Check your radiator/condenser fan operation NOW

smomarkiv · Jun 26, 2017

smomarkiv said:
Between T14-6 and negative terminal of the battery is 0.1ohms, 20ohms if the battery is fully connected. The rest I'll get out and check in the next couple days, including checking resistance on the ambient temp sensor. Work has been keeping me busy, but I'll check all that Sunday, probably. Thanks!

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Ok, I spent some time on it yesterday, and here's what I found regarding your questions:

Regarding the ambient temperature switch:

Resistance between pins T14-5 and T14-14 were 0.626Kohms when I started. It was roughly 75 degrees outside. I put the switch in the freezer for a while, and after that it read 12.2Kohms, dropping immediately and steadily. It dropped as far as 1.2Kohms before my arms got tired of holding the probes and I gave up.
While the sensor was in the freezer and I was waiting, I jumpered the connector with a paperclip, and resistance was jumping all around between 0.0 and 0.7ohms.

I checked the different ground connections you said I should check. Between T14-6 and N25 jumps around between 0.3 and 1.0ohms. Same for T14-6 to driver side fan. Same for T14-6 to passenger side fan. Between G65 and ground is 0.0ohms.

I also went back and looked at T14-3 while I was in there. That is supposed to be and 11v reference voltage from the ECU. Once upon a time I saw 12v there, but now I'm seeing 56.6mV DC. Readings from T14-3 when unplugged as follows: continuous to battery negative, 300ohm resistance, 53% duty cycle, 0.5mVac, 0.8Khz. None of those look correct based on Dan's write-up. Supposedly this can be grounded due to a loss of throttle basic settings, but the car drives fine, plus according to what I'm reading the car will do a throttle basic settings every time you turn it on anyway. I can get someone with VAG-COM to do a throttle basic settings, but I don't have a lot of hope for it. Also, if that is the problem, supposedly raising throttle above 2500rpm will make it work, and that doesn't work.

I'm still at a total loss. I guess I'm going to do a throttle basic settings and just rule that out.

SilverGhost · Jun 27, 2017

The ambient temperature sensor and its wiring looks good.

T14/3 is probably a serial buss wire and shares info between FCM and ECM about G65 pressure, engine load, engine overheat condition, etc. Duty cycle or AC voltage will tell you if something is happening.

That ground bothers me. Should still be near 0ohms with battery connected. Can you please check voltage on that wire T14/6 (pick a connector) to battery ground. Key on and Key off.

If all else checks out then ECM will still store a code indicating AC enabled or why it is disabled. Just have to try the MVBs in the 50s or higher 60s. I think VCDS will pop up a box to tell you what the 2 digit code means.

Jason

wonneber · Jun 27, 2017

smomarkiv said:
Between T14-6 and negative terminal of the battery is 0.1ohms, 20ohms if the battery is fully connected. The rest I'll get out and check in the next couple days, including checking resistance on the ambient temp sensor. Work has been keeping me busy, but I'll check all that Sunday, probably. Thanks!

Sent from my SM-G930P using Tapatalk

You shouldn't be testing resistance on a powered circuit.
Will not provide meaningful readings.
Do a voltage drop test with the car running, AC on, on fan full.
Measure from the battery post (my preference) and the T14-6 point you referenced.
I would not want to see more then a few tenths of a volt.

smomarkiv · Jun 28, 2017

SilverGhost said:
The ambient temperature sensor and its wiring looks good.

T14/3 is probably a serial buss wire and shares info between FCM and ECM about G65 pressure, engine load, engine overheat condition, etc. Duty cycle or AC voltage will tell you if something is happening.

That ground bothers me. Should still be near 0ohms with battery connected. Can you please check voltage on that wire T14/6 (pick a connector) to battery ground. Key on and Key off.

If all else checks out then ECM will still store a code indicating AC enabled or why it is disabled. Just have to try the MVBs in the 50s or higher 60s. I think VCDS will pop up a box to tell you what the 2 digit code means.

Jason

Ok, here's what I got. Checked between T14/6 and battery negative:
Connector connected, key off - jumps between 20.9 and 21.3 ohms
Connector connected, key on - between 249.2 and 250.6 ohms
At this point I pulled the key and it read 79ish for say 30 seconds or so before dropping back down to the 20-21 range
Connector disconnected, key off - between 16.7 and 17.2 ohms
Connector disconnected, key on - between 226 and 233 ohms

I checked again what would happen if I disconnected the battery. Between T14/6 and battery negative terminal, disconnected - between 0.0 and 0.7 ohms

To answer wonneber -

T14/6 to battery negative showed 1.3mV car off
With car on, A/C on, fan full, it climbed steadily to around 140mV, then the engine settled into idle and it dropped to between 70 and 71mV.

I don't know what all this says about what I should do next. But I'll be meeting a friend with VCDS in a few hours to try running throttle basic settings and see if anything happens. I'll report back.

BobnOH · Jun 28, 2017

Ohms are a unit of measure for resistance. They can tell you the capacity of a circuit or the condition of a a component. All automotive circuits complete their connection to ground. The ground can be a wire or a simple connection to another grounded component (ie body).
So I said all that to say this, I don't know what you're testing with those live circuits. I glanced at the links up on Post #1 and they refer to check voltage at various spots.

wonneber · Jun 28, 2017

smomarkiv said:
Ok, here's what I got. Checked between T14/6 and battery negative:
Connector connected, key off - jumps between 20.9 and 21.3 ohms
Connector connected, key on - between 249.2 and 250.6 ohms
At this point I pulled the key and it read 79ish for say 30 seconds or so before dropping back down to the 20-21 range
Connector disconnected, key off - between 16.7 and 17.2 ohms
Connector disconnected, key on - between 226 and 233 ohms
I checked again what would happen if I disconnected the battery. Between T14/6 and battery negative terminal, disconnected - between 0.0 and 0.7 ohms
To answer wonneber -
T14/6 to battery negative showed 1.3mV car off
With car on, A/C on, fan full, it climbed steadily to around 140mV, then the engine settled into idle and it dropped to between 70 and 71mV.
I don't know what all this says about what I should do next. But I'll be meeting a friend with VCDS in a few hours to try running throttle basic settings and see if anything happens. I'll report back.

The 140 mV is .14 volts.
I wouldn't worry about that.
Will wait to see what VCDS indicates.
Did you open the harness to look for frayed wires?

SilverGhost · Jun 29, 2017

What do you mean "connector connected"? T14 plugged into FCM?

Checking voltage drop needs everything connected and a load on the circuit to be meaningful. Ohms test needs everything disconnected and no load on the circuit to be meaningful.

I usually don't see voltage drops that high unless I'm check charging circuit under full load (90-140A) or starter.

Lets see what VCDS says...

Jason

wonneber · Jun 29, 2017

I've seen more then a volt drop on lighting circuits with a bad ground.
Back in the late 70's (iIrc) some GM cars had a welded connection that broke in the rear tail light sockets.
Car's would fail inspection because the brake/parking light would go out if the lights were on and the brake applied.

InfoSec · Jun 29, 2017

Dan:

I've gone through the steps (as well as I could) and I replaced by driver's-side fan. Both fans come on as they should with key on, a/c switch on, fan speed = 1, and I have an open circuit on my coil. Ordered the coil, clutch, and bearing. I'm pretty sure the bearing is fine a the compressor spins freely with the car off, I do want to replace the clutch and coil, but my question is, can this be done with the compressor still on the car? I cannot find anybody in the Grand Rapids, Michigan area that wants to just replace the clutch/coil for me. Most folks want to replace at the very least the whole compressor. I don't want to do that. Since I cannot evac the refrigerant myself, is it possible to replace the clutch/coil with the compressor still in-place, and by that I mean, w/out dropping it down from it position after you remove the two 16MM bolts? If I get a pulley-puller, clutch tool, can this be done? I'm wondering if I remove the right tire, inner fender well, any I/C piping, would the clutch face be accessible???

-Mike in GR.

jiveabillion · Jun 29, 2017

InfoSec said:
Dan:

I've gone through the steps (as well as I could) and I replaced by driver's-side fan. Both fans come on as they should with key on, a/c switch on, fan speed = 1, and I have an open circuit on my coil. Ordered the coil, clutch, and bearing. I'm pretty sure the bearing is fine a the compressor spins freely with the car off, I do want to replace the clutch and coil, but my question is, can this be done with the compressor still on the car? I cannot find anybody in the Grand Rapids, Michigan area that wants to just replace the clutch/coil for me. Most folks want to replace at the very least the whole compressor. I don't want to do that. Since I cannot evac the refrigerant myself, is it possible to replace the clutch/coil with the compressor still in-place, and by that I mean, w/out dropping it down from it position after you remove the two 16MM bolts? If I get a pulley-puller, clutch tool, can this be done? I'm wondering if I remove the right tire, inner fender well, any I/C piping, would the clutch face be accessible???

-Mike in GR.

Yes, you can replace the clutch, pulley and coil without disconnecting the compressor from the AC system. I did it 2 days ago on my 2003 Jetta TDI.

I did have to unbolt the compressor and let it hang down so I could get my snap ring tool where it needed to go to get the snap ring off and pull the pulley out. I had to pry the compressor out of its place after removing the bolts and I had to use my jack and some more prying to get it back where it goes, but unbolting it did make replacing the pulley and coil easy.

Make sure you shim the clutch correctly. I ended up using the shim that was already on the compressor instead of the ones that came with my kit because it fit on the spindle better and was exactly the right thickness needed.

The clutch works great now, but I still don't get cold air. I'm going to have to try recharging it again.

UPDATE: I just recharged it again using a better hose and gauge and it blows cold air now!

smomarkiv · Jun 29, 2017

Yes, when I say "connector connected," I mean the T14 connector connected to the FCM. Likewise "unconnected" means T14 not connected to FCM.

So I had a buddy run throttle basic settings with VCDS. It all checked out ok, but it didn't change anything as far as the A/C or fans, they still refuse to come on. His battery on the laptop died and he had to leave, so we didn't run a full scan. I'll be away for the weekend, but next week I'll get back together with him to run a full scan so I can report back what that says.

I opened up the T/14 and T/4 harness all the way back to under the battery tray, everything looked kosher there.

I'm talking to a tech who wants me to pull the rain tray and look at the harness there, check the other end of the T14/3 wire that comes from the ECU, make sure nothing's broken there. I'll probably do that next, but I think that wire's intact. After all, it shows continuity to ground, so the connection is good, the problem is just that the ECU is grounding it to command compressor off, as it is designed to do, I just don't know why it's insisting on doing that.

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InfoSec · Jun 30, 2017

jiveabillion said:
Yes, you can replace the clutch, pulley and coil without disconnecting the compressor from the AC system. I did it 2 days ago on my 2003 Jetta TDI.

I did have to unbolt the compressor and let it hang down so I could get my snap ring tool where it needed to go to get the snap ring off and pull the pulley out. I had to pry the compressor out of its place after removing the bolts and I had to use my jack and some more prying to get it back where it goes, but unbolting it did make replacing the pulley and coil easy.

Make sure you shim the clutch correctly. I ended up using the shim that was already on the compressor instead of the ones that came with my kit because it fit on the spindle better and was exactly the right thickness needed.

The clutch works great now, but I still don't get cold air. I'm going to have to try recharging it again.

UPDATE: I just recharged it again using a better hose and gauge and it blows cold air now!

Thanks for responding!!! I'll have to remove my diesel geek side skirt (at least, I think I'll have to remove it). I was hoping I could remove the tire, inner fender well cover, charge tube, in order to get at the front of it w/out having to actually take out the compressor bolts. But if that's not a feasible way to do it, then I'll have to drop it down... I have read (not only your comments about it) other threads that it's a pain to do that, but it will save me having to pay someone to vacuum and recharge the system... I'll just man-up and give it a whirl. Thanks!!!

DanG144 · Jul 4, 2017

I am just getting back from a month in a wilderness area, and have not had time to totally catch up.

But you can probably just cut the wire from the ECU that grounds to command the OFF status.

The ECU generally does this (as you seem to know) due to full throttle demand or overheating of the engine.

If your throttle and pedal tests are ok, and your engine temperature sender is good then you may have a problem in the ECU. At least one other person has had this, and cut the wire to restore operation. I would not lose any sleep over operating with that feature gone.

Remember that the ECU will often substitute readings in the measuring blocks without warning you of the substitution. I would pull the engine coolant temperature sensor and check the resistances of both elements.

Dan

smomarkiv said:
Yes, when I say "connector connected," I mean the T14 connector connected to the FCM. Likewise "unconnected" means T14 not connected to FCM.

So I had a buddy run throttle basic settings with VCDS. It all checked out ok, but it didn't change anything as far as the A/C or fans, they still refuse to come on. His battery on the laptop died and he had to leave, so we didn't run a full scan. I'll be away for the weekend, but next week I'll get back together with him to run a full scan so I can report back what that says.

I opened up the T/14 and T/4 harness all the way back to under the battery tray, everything looked kosher there.

I'm talking to a tech who wants me to pull the rain tray and look at the harness there, check the other end of the T14/3 wire that comes from the ECU, make sure nothing's broken there. I'll probably do that next, but I think that wire's intact. After all, it shows continuity to ground, so the connection is good, the problem is just that the ECU is grounding it to command compressor off, as it is designed to do, I just don't know why it's insisting on doing that.

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cabot · Jul 4, 2017

So, in the first post, there is a description of the what each pin goes to on the connectors. This is useful information but not what you really need to be able proceed though the troubleshooting PDF. The first post should have a simple diagram of each connector with the pins numbered. Every time I fool with the AC on one of these things, I've forgotten how the pins are all numbered and spend hours looking for this.

DanG144 · Jul 4, 2017

Page 9 and 10 of the linked PDF has the pictures showing the numbering of the T4 and T14 connectors and battery fuse box.

You are welcome to cut the photos out and post them if you wish. Heck, if you will post them, I will link to them. I am long past the capacity of my account here, and must delete some photo every time I post a new one.

Each of the connectors has the numbering on them, you know. You just need a bright light and magnifying glass to read them.

InfoSec · Jul 5, 2017

Dan et al:

Replaced both of my large fans on my 03 Jetta and 03 Golf. All pressures are within spec. Was able to drop the compressor and remove the clutch face, pulley, and coil w/out too much trouble. My belated Xmas presents of a pulley puller, and a snap-ring plier set w/ multi-angled tips were Godsends. Very useful. I did not have any trouble removing the compressor from its location after the two 16mm bolts were removed. I was able to jostle it free and set it on top of a 5-gal pail in order to remove and replace the clutch/pulley/coil. The only tough part of the ordeal was having to sit half-supine in order to remove the snap rings and the pulley. Putting everything back together was actually quite easy and quick. A/C temp at the vent was reading 38F. So very happy. Now I can think about selling it again!!!

Thanks for a wonderful post and to whose that may have responding to my questions.

-Mike in GR.

smomarkiv · Jul 6, 2017

DanG144 said:
I am just getting back from a month in a wilderness area, and have not had time to totally catch up.
But you can probably just cut the wire from the ECU that grounds to command the OFF status.
The ECU generally does this (as you seem to know) due to full throttle demand or overheating of the engine.
If your throttle and pedal tests are ok, and your engine temperature sender is good then you may have a problem in the ECU. At least one other person has had this, and cut the wire to restore operation. I would not lose any sleep over operating with that feature gone.
Remember that the ECU will often substitute readings in the measuring blocks without warning you of the substitution. I would pull the engine coolant temperature sensor and check the resistances of both elements.
Dan

Hey Dan! Thanks so much for the help! I'm getting pretty close to cutting that wire, especially if it will finally make it work, but I'm still hoping I can figure out the problem before I resort to that. Yesterday I took a look at the wiring going to the G62 green top coolant temp sensor. The wires were all frayed at the connector. So I pulled and re-pinned all four there. No change in my symptoms however. I measured half that sensor, it seems to be operating within spec. It's also pretty new, it was replaced this winter as an earlier attempt to fix the A/C. I'm told the two pins on the round end of the sensor send the temp info to the ECU and the two pins on the square end send the temp info to the dash. I measured the two pins on the round end, got 1.73Kohms when the engine was cold. Started it up, and watched it drop continuously as far as 220ohms before I shut the car off. Tonight I should be able to get the car read by VCDS, see if there's anything in there that somehow helps me. I'm going to go inspect the wiring again, maybe pull the pin for T14/3 and just see if that makes it work.

Genesis · Jul 6, 2017

VCDS will tell you what the ECU thinks the coolant temperature is off the part of the sensor that feeds it (as opposed to the part that feeds the cluster's needle), yes. I would not cut that wire because odds are IF it is being commanded off finding the cause is not going to be very difficult *and* if the ECU thinks the engine is hot enough to command the AC "off" then it also is probably making bad decisions that will hurt drivability, fuel economy or both. (That certainly is the case when it thinks the engine is too cold due to a sensor problem -- from direct experience!)

smomarkiv · Jul 6, 2017

Genesis said:
VCDS will tell you what the ECU thinks the coolant temperature is off the part of the sensor that feeds it (as opposed to the part that feeds the cluster's needle), yes. I would not cut that wire because odds are IF it is being commanded off finding the cause is not going to be very difficult *and* if the ECU thinks the engine is hot enough to command the AC "off" then it also is probably making bad decisions that will hurt drivability, fuel economy or both. (That certainly is the case when it thinks the engine is too cold due to a sensor problem -- from direct experience!)

Thanks, Genesis. I am inclined to agree with you that finding the cause for the ECU commanding A/C off is better than finding a work-around. Unfortunately I can't agree with you that finding the cause should be easy. It's taken me 7 years to get to this point and I still don't have any answers. There are only 2 reasons the ECU commands compressor off, and they are: 1. full throttle (or loss of basic throttle settings) and 2. overheat. Neither of those situations is true, so I'm just at a total loss as to why it's commanding compressor off. If I'm reading Dan's troubleshooting document correctly, it's commanding off via the wire that it uses to command off for throttle issues. But I've reset throttle basic settings and it didn't help, and I've revved the engine above 2500rpm and it doesn't help... There just doesn't seem to be any answer for me that fits in with the established troubleshooting procedures.

SilverGhost · Jul 10, 2017

Actually there is a list (somewhere) of about 15 or more AC compressor off codes. Usually when I'm working with the scan tool the test plan (VAG scan tool) will give a list to go with the code.

I'll try to remember to read my car when I get home and post up a list.

Jason

DanG144 · Jul 10, 2017

On the Mark IV cars, the subject of this thread, the scan tool is of very little help. There is no list of codes.

For the Mark V and up, the scan tool is of great help, with lists of codes (both shut off and DTC) available and posted on this site.

Nevada_TDI · Jul 11, 2017

I could have saved myself a lot of grief if I would have ever read this thread at anytime in the last 9 or so years.. Just recently at 262k plus miles, my A/C started acting up. I thought it may have needed a recharging, but when I put a gauge on the suction side and the pressure was up over 150 PSI, I knew something was wrong. I apparently had not listened for the fans running in a very long time, and when I posted in a different thread about my non-running fans and high suction pressure I was basically told to get my fan problem sorted out first. They were both dead, and the small fan had apparently gotten so hot that the center of the fan hub was almost one inch lower than the bearing center. A trip to Pick-N-Pull fixed my fan problems; neither fan was dead quiet when running but they spin for 5 or 6 seconds after the power is turned off, and for $52.00 out the door for the pair I could not be more pleased. Thanks again to everyone on this website who has taken the time and done the hard work to simplify solutions to our various problems in our aging TDI's.

SilverGhost · Jul 13, 2017

It's been that long I forgot about that. Just checked mine and you get two things - feed back that you asked for AC (pushed the button) and feed back that the compressor is engaged and working. Can't remember if one of those will indicate the ECM blocking AC or not. EDC 15 doesn't help much.

Jason

DanG144 · Jul 17, 2017

Rgdylan1 said:
Dan,
I just registered with TDI club so i could try and solve my AC issues but it seems i am not allowed to post yet? I want to post in the AC sticky so maybe you can provide some insight on why i cant post or why my fans dont work lol.
I bought a 2002 jetta recently and have been finding the previous owners horrible work all over the car (please dont get me started). I recently discovered that the AC is not working (what a suprise - the engine bay is a mess) so i of course found your trouble shooting guide and atttempted to follow it as best i could. Unfortunately, i was unable to come to a conclusion regarding my problem. With that being said i do not own a dmm that reads duty cycle so i could have missed something there.
A little back ground on what i know right now.
1.) I turn the key to ON and AC on with low blower fan speed and my radiator fans DO NOT come on.
2.) I jumper pins 1 and 2 on the thermo switch plug and the fans DO NOT come on.
3.) I jumper pins 2 and 3 on the thermo switch plug and the fans DO NOT come on.
4.) I do have 12 volts (11.7 V - is that enough? it matches my battery terminal voltage with the vehicle off) present at the thermo switch plug.
5.) The only way i could get the fans to run was to jumper them directly to the battery...both fans ran at both speeds.
6.) I replaced the Fan Control Module because it looked like the PO had messed with it bad (looked like went inside the FCM?).
Now for the part that i find most interesting: I didnt notice this until after replacing the fcm but when i jumper pins 1 and 2 on the thermo switch plug i can see the small cooling fan budge ever so slightly like it wants to move but then it stops and just starts buzzing. Ever seen this before? I asked the previous owner about this and he said at one time he replaced the "B5 resistor or something." I cant find anything on that; he said he "fought it once with the (kerma) Q loader and it said which relay or resistor it was." I wasnt aware that the Q loader could do that.
I do have a question regarding your trouble shooting procedure. When you refer to the "test light" what kind of voltage are we expecting?
I apologize for sending a PM but i have been chasing this problem for a couple of weekends/weeks now and i am begining to lose my patience. I will prevail, however. If you want to post this to the sticky feel free, that would be great. Either way i would appreciate any insight and help on this issue.
Thanks in advance,

Dylan,
No problem with the PM; I get several a week on this topic.
It sounds to me as if you may have a problem with the wiring. Too much voltage loss. This problem is usually in one of three places due to too much voltage loss at high current draw
The voltages can appear normal at no current draw.
1) Most prevalent- bad connections at the battery terminal fuse panel causing low voltage delivery to the fans. The problem is usually right at the 30 amp fuse that powers the slow speed fans. Take the fuse panel apart and repair it (clean it up, maybe tin the contact areas with solder) or replace it.
2) There is a splice in the heavy wiring to the fans. This has started to corrode apart on some older cars, especially those in wet or rust belt areas on cars with no engine belly and side pans. You can take this apart and solder it again, once you find it in the wire bundle.
3) Bad grounds. Remove the battery tray and physically clean (wire brush) the grounds. Don't just look at them.
I bought a 40 amp automotive circuit breaker (auto reset) and installed it instead of my 30 amp slow speed fuse. I powered it from one of the clean bolted connections on the fuse panel. Others have replaced the wiring right down to both the radiator thermoswitch and the fans.
Do a very thorough visual inspection first, repair anything that shows up, then while trying to power the fans (so with everything plugged in and hooked up) measure the voltage at your fan terminals and T4 terminals on the FCM.
11.7 is very low battery voltage, by the way. Clean your battery terminals and check your voltage with the engine running to ensure your alternator is working properly. 11.7 is plenty to run the fans, though. Just mentioning it as a side bar.
You should be able to post within a few hours.

Jesterking · Jul 17, 2017

It's been over a year since i had a very similar problem...
Locating the splice in the wire bundle wasn't too much of a hassle, once I wrapped my head around the fact that there was a "y" splice from the factory hidden in the bundle behind the battery.. I stopped asking WHY? and fixed it..A/c has been working great ever since ... Thanks Dan for your assistance!!

smomarkiv · Jul 18, 2017

smomarkiv said:
Hey Dan! Thanks so much for the help! I'm getting pretty close to cutting that wire, especially if it will finally make it work, but I'm still hoping I can figure out the problem before I resort to that. Yesterday I took a look at the wiring going to the G62 green top coolant temp sensor. The wires were all frayed at the connector. So I pulled and re-pinned all four there. No change in my symptoms however. I measured half that sensor, it seems to be operating within spec. It's also pretty new, it was replaced this winter as an earlier attempt to fix the A/C. I'm told the two pins on the round end of the sensor send the temp info to the ECU and the two pins on the square end send the temp info to the dash. I measured the two pins on the round end, got 1.73Kohms when the engine was cold. Started it up, and watched it drop continuously as far as 220ohms before I shut the car off. Tonight I should be able to get the car read by VCDS, see if there's anything in there that somehow helps me. I'm going to go inspect the wiring again, maybe pull the pin for T14/3 and just see if that makes it work.

Hey, so I'm still no closer. I pulled pin T14/3 out of the connector to see if that would work, but no change. Still no fans, no A/C. I put it back in, since it didn't change anything. Last time I measured that pin, on July 6, it no longer read continuous with ground, like it used to, with the key on, A/C on. It read 066.0mV, 0.75Kohms, 30% duty cycle, bouncing around a bit. It still feels like the T14/3 is a problem somehow, the way I understand it I should be getting 11v reference voltage, and instead it's 066.0mV...

DanG144 · Jul 18, 2017

I think the voltage actually comes from the FCM, not the ECU...for that control signal.

Look at the above posts, I think you may be having a wiring problem - a high resistance connection causing a voltage drop under load. While this is conjecture, I would act on it.

Unplug both your fans and see if the compressor clutch engages. If it does, this is because the voltage is dropping too far (at T4a/3 and/or T4a/1 when the fans try to start. Of course you cannot operate the system this way, but it may help with the troubleshooting.

Those splices are failing pretty frequently these days on rust belt cars, and cars in wet areas.

smomarkiv · Jul 25, 2017

DanG144 said:
I think the voltage actually comes from the FCM, not the ECU...for that control signal.

Look at the above posts, I think you may be having a wiring problem - a high resistance connection causing a voltage drop under load. While this is conjecture, I would act on it.

Unplug both your fans and see if the compressor clutch engages. If it does, this is because the voltage is dropping too far (at T4a/3 and/or T4a/1 when the fans try to start. Of course you cannot operate the system this way, but it may help with the troubleshooting.

Those splices are failing pretty frequently these days on rust belt cars, and cars in wet areas.

Excellent, I will try that next! Thank you!

AnotherPerson · Jul 26, 2017

Another fan failure to note here. My large one I checked while having a strange randomnidle vibration and when I gave it a little push it spun up slowly. Figures my Subaru loaner gets returned first thing in the morning.

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AnotherPerson · Jul 27, 2017

Confirmed that the fan couldn't spin itself up anymore. Apparently the high speed fans would kick in and once it got going and spun to low it kept going. Why can't we just get decent fans out there. :/

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Check your radiator/condenser fan operation NOW

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