Check your radiator/condenser fan operation NOW

[kball]

This helped me find it was the ambient sensor causing all my headaches. The harness was broken.
https://forums.ross-tech.com/showthread.php?14597-mk4-Fan-Control-Module-(J293)-chart-and-A-C-tips

 

[E31]

No engine cooling fans at low or high speed

2004 Volkswagen Beetle convertible 5 speed
I have no low speed fans when I turn on the ac and blower. To try and resolve the problem I've replaced the following:

FCM (twice), the thermoswitch on the radiator, along with the fusebox over the battery.As well as the fan unit itself.

I've attempted trouble shooting the problem with the instruction in this thread. I have signal at the FCM (T14/8) when the ac switch and blower are on but the fans do not turn on. All fuses are good including 5,16, and 25 inside the car.
On T4/1 and T4/3 I have 12 volts. I do not have 12 volts on T4/2 which is required for low speed fans. I took the connector off the thermoswitch and jumper pins 1 and 2, the fans turn on. However when I jumper pins 2 and 3 following the instructions in this thread, I do not get high speed. I took off the connectors for the fans and applied 12v directly, both high and low speeds are working.

Not sure how the lack of high speed would prevent the low speed fans from coming on but this is what I see so far. Also in the pinout for the T$ and T14 connectors for the FCM, it indicates there's another signal required for the low speed, T14/3 for a ground from the ECM when the engines under heavy load. If this is constantly ground would that cause my problem?

I could really use some help here.

 

[Nuje]

Assuming the radiator fans are turning...

Behind the glove compartment is the interior fan HVAC blower motor (looks like a hamster wheel), which has a little tray attached to it with a resistor pack in it. The resistor is what takes the "blow air" signal and dials it back for speeds 1, 2, 3. Speed four is "wide open", which is what you have when the resistor pack is blown.

You can replace the resistor pack alone, but typically, it blows because there's too much resistance (e.g. bad bearings) on the hamster wheel. So best to replace both.

It's been a while since I fixed a Mk4 with this issue, and it wasn't a Beetle, but I don't remember it being too hard; some skinned knuckles from confined spaces IIRC, but doesn't require any fancy-pants tools to do the job.

 

[E31]

Assuming the radiator fans are turning...

Behind the glove compartment is the interior fan HVAC blower motor (looks like a hamster wheel), which has a little tray attached to it with a resistor pack in it. The resistor is what takes the "blow air" signal and dials it back for speeds 1, 2, 3. Speed four is "wide open", which is what you have when the resistor pack is blown.

You can replace the resistor pack alone, but typically, it blows because there's too much resistance (e.g. bad bearings) on the hamster wheel. So best to replace both.

It's been a while since I fixed a Mk4 with this issue, and it wasn't a Beetle, but I don't remember it being too hard; some skinned knuckles from confined spaces IIRC, but doesn't require any fancy-pants tools to do the job.

Thanks for the quick response Nuje. Is there a way for me to check whether the resistor pack is good? What would be the ohm reading and can I find the removal procedure in Bentley Manual?

 

[Maccapro]

Mine is working, but I had to fix it last year, the whole system 1000€-1200€ aproximately

 

[Nuje]

Thanks for the quick response Nuje. Is there a way for me to check whether the resistor pack is good? What would be the ohm reading and can I find the removal procedure in Bentley Manual?

I can't remember off-hand, but I think the reading was the same as if the little resistor (available for like $.25 at Radio Shack if it still existed) was just not there; that is, an open circuit. Or possibly as if you were on two ends of a continuous wire - can't remember the details; in any event, it was obvious that the resistor was the issue.

Edit:
Link to how-to thread
Link to .pdf on removal contained within above thread

Either way, my experience was that I replaced the little resistor - which lasted a little while then failed again. Then replaced the resistor pack....which again, did the job for a little while, then failed. (Like I mentioned, the reason the resistor pack fails is typically that it's getting too much resistance from bad bearings or whatever on the blower motor).

So, I then replaced the blower motor and replaced the resistor pack again...and that worked until I sold the car (18months+).

 

[E31]

I can't remember off-hand, but I think the reading was the same as if the little resistor (available for like $.25 at Radio Shack if it still existed) was just not there; that is, an open circuit. Or possibly as if you were on two ends of a continuous wire - can't remember the details; in any event, it was obvious that the resistor was the issue.

Edit:
Link to how-to thread
Link to .pdf on removal contained within above thread

Either way, my experience was that I replaced the little resistor - which lasted a little while then failed again. Then replaced the resistor pack....which again, did the job for a little while, then failed. (Like I mentioned, the reason the resistor pack fails is typically that it's getting too much resistance from bad bearings or whatever on the blower motor).

So, I then replaced the blower motor and replaced the resistor pack again...and that worked until I sold the car (18months+).

Nuje thanks again. I've ordered the blower and resister pack and will update once installed.

 

[dloomis]

Holy crap was this job a roller coaster. After determining that both fans were non-functioning (via direct power method), I ordered new fans and got them installed without too much fuss. I ended up ordering FEBI BILSTEIN fans from RMEuropean...the quality seems awesome and the price was super cheap. I reused all brackets.

So....I finished up everything and just when I was reinstalling the bottom engine cover I notice that the driver axle boot was torn to shreds. OK, I've never replaced an axle boot so I figured it would be a good learning experience. Technically it wasn't hard job but CHRIST was that axle hard to get out of the hub. I think I might have damaged the wheel bearing getting it back in, cause wouldn't you know it now I have a wheel bearing to replace too. I've never swapped a wheel bearing out either so now there's even more scope creep to deal with.

Fast forward through that and I FINALLY get everything put back together and working. Thanks again to this thread and the awesome community. I couldn't do it without you.

P.S. New Beetles are terrible to work on! So much crap to remove to get to the part you need. Sigh.

 

[E31]

I can't remember off-hand, but I think the reading was the same as if the little resistor (available for like $.25 at Radio Shack if it still existed) was just not there; that is, an open circuit. Or possibly as if you were on two ends of a continuous wire - can't remember the details; in any event, it was obvious that the resistor was the issue.

Edit:
Link to how-to thread
Link to .pdf on removal contained within above thread

Either way, my experience was that I replaced the little resistor - which lasted a little while then failed again. Then replaced the resistor pack....which again, did the job for a little while, then failed. (Like I mentioned, the reason the resistor pack fails is typically that it's getting too much resistance from bad bearings or whatever on the blower motor).

So, I then replaced the blower motor and replaced the resistor pack again...and that worked until I sold the car (18months+).

Nuje replaced both the blower and resistor pack and the fans still do not come on at low speed when the interior fan selector's on and the ac button's pushed. I checked the resistance between each of the 4 points in the resistor pack with the two points with the diode between them of the old unit and compared with the new unit and they looked the same. I installed anyway cause the issue could happen under load. On the FCM T14/8 is where the signal from the fan blower (E9) and the AC switch (E35) should occur. In the J293 pinout there is a mention of a S225 fuse, I've not been able to find this. Also T14/3 is another signal needed for T4/2 of the FCM to provide 12v for the low speed fan power. T14/3 is the AC load cut-out signal. Is there a way to check this? Has this ever presented a problem?

 

[Nuje]

Another thread with other ideas / suggestions:
http://forums.tdiclub.com/showthread.php?t=371910

 

[E31]

Another thread with other ideas / suggestions:
http://forums.tdiclub.com/showthread.php?t=371910

The thread you're referencing appears to address problems when the blower does not spin or spins only on setting #4. This is not my problem. I have all four speeds working before and after replacing the blower and resistor pack. No fuse appears blown but I don't have the low speed cooling fans working when AC and a blower fan speeds selected. Again, the things replaced to fix has been the fan unit, the fuse box, the thermoswitch on radiator, the FCM (twice), and now the blower and resistor pack. And again I'm asking, in the J293 pinout there is a mention of a S225 fuse, I've not been able to find this. Also T14/3 is another signal needed for T4/2 of the FCM to provide 12v for the low speed fan power. T14/3 is the AC load cut-out signal. Is there a way to check this? Has this ever presented a problem? Also does anyone know which wires to check from the fuse box to the FCM and to the thermoswitch for continuity?

 

[E31]

When I pull fuse #16, the fans come on at low speed as they should, however when I turn the car off, the fans don't. They continue to run until I pull the T14 harness of the FCM. Fuse #16 controls the power water pump which I don't have and the AC clutch. I tried removing the connector from the clutch but still have the same problem.

UPDATE After researching found that is fuse 16 is blown (or removed) it will cause the fans to run continuously so this is no the problem.

 

[seaglf]

Fan speed

I can turn my ac on high with key on, and both fans work, but how do I know if it's high speed or low speed? Also I tried to put some refrigerant with dye to check for leaks , but it won't except any.

 

[ToxicDoc]

I can turn my ac on high with key off, and both fans work, but how do I know if it's high speed or low speed? Also I tried to put some refrigerant with dye to check for leaks , but it won't except any.

Fans should not come on with the key off. VW is crazy with their circuit logic - check the fuses.

 

[Genesis]

I can turn my ac on high with key off, and both fans work, but how do I know if it's high speed or low speed? Also I tried to put some refrigerant with dye to check for leaks , but it won't except any.

If the key is off and the fans are running check the fuses -- there's a specific fuse that often leads to this (but I don't remember which one it is.)

If the system has a reasonable amount of charge in it it will not take refrigerant without the compressor running to suck down the low side pressure, as the static pressure (with it off) is high enough to prevent it.

 

[seaglf]

Sorry I don't know why I wrote "off" I meant on, because I was following the instructions from the first part of this thread.

 

[CameraJack]

Hi Guys,

I made another thread but I was directed here so I hope somebody can help me shed some light on my situation.

2002 PD130 Estate/Wagon, Climatronic, 09A Tiptronic.

I have no AC or radiator fans (either slow or fast). When 12V is momentarily applied to the compressor clutch, it engages and blows cold air in the cabin. So it is an electrical issue.

When testing my rad fans, slow works when the thermoswitch is bridged. Fast does not but I will look into that later, it seems like slow is the most important and fast is rarely utilised in TDIs (especially in the cool climes of the UK).

It seems like there are only a couple of things that will inhibit both compressor clutch and rad fans.

The most likely culprits are the pressure switch and the ambient temp sensor.

I followed some of the diagnosis procedure and here is what I got:

9 volts at the compressor plug with no load. Did not test under load.
3.2V duty cycle on T14/2 from the pressure sensor. Seems to be in range.
Battery power to T14/4 is good.
10 ohms to ground on T14/6 (seems way too high to me - would splicing in a new ground here help?)
Switched battery power to T14/9 is good.
14 ohms to ground through compressor on T14/10. 4 ohms through the compressor is supposed to be good. I imagine my seemingly bad ground is what is increasing the resistance.
No continuity between T14/5 and T14/14 for ambient temp sensor F38.

Seems to me like making a new ground for the FCM and checking out my ambient temp sensor might be my way forward.

Except that I cannot find my ambient temp sensor. Where the hell is it?! I've looked and felt all around where my pollen filter is under the windscreen and there isn't a hint of it up there. No wires or anything.

Any help would be appreciated. I'd love me some nice cool AC for the summer.

Thanks in advance.

 

[seaglf]

Fan

As I reposted when I turn the key ON but not starting the car and turn AC to low the fans come on. But I don't know how to tell if they are low or high speed.The reason I ask is because I read somewhere that if they come on high then it could be an indecation of something wrong.

 

[CameraJack]

A small update on my AC/fan saga from the post before last.

After further inspection it turns out that T14/5 and T14/14 and jumped with a short length of wire on my FCM plug. I was somehow mis-reading my meter before and when retested it showed continuity. I guess VW decided the ambient temp switch wasn't necessary in the UK market. This would explain why I spent the best part of an hour searching for it in the cowl under the windscreen to no avail.

I made a new ground for my FCM and had no improvement. With the new ground in place I tested resistance through the AC clutch, expecting now to see the correct ~4ohms rather than the ~14ohms before, assuming that the AC clutch grounded through the FCM. It still read ~14ohms. Upon further checking of the FCM pin-out, there is no return from the AC clutch, which means it grounds elsewhere. Hmmmm.

I unplugged the fans and checked the grounds there as well. ~10ohms to ground on both chassis-side fan plugs.

I looked up the ground point table and low-and-behold; the FCM, AC clutch, and rad fans all ground at the same point - point 12. This point is shared by the headlights, front indicators, etc, which all work fine. So either there are two ground wires to the same point and there is a contact issue at the point, or there is a problem with the wiring between the ground point and everything else.

Looks like I'm digging under the battery again tomorrow night! Annoyingly I pulled all the battery out about a month ago and cleaned up all the grounds I could see under there. And because it's an Auto there's a ton of massive conduit under there for all the gearbox wiring which gets in the way making it a massive PITA. Lovely. Fingers crossed there's a smoking gun and I don't have to go tracking down the ground cables.

I hope this is helpful for anyone else having similar issues. I will keep it updated.

 

[CameraJack]

FINALLY AN END TO MY SAGA.

Spent another three hours on this today. I moved the two grounds for front lights and rad fans/clutch/FCM to the other ground point to rule out an issue with the point itself. I had good resistance readings through the ground. Was now reading good resistance through the rad fan ground, clutch ground, and FCM ground when I wasn't before.

Chased my tail for a good hour because I was reading 10 ohms between the negative battery terminal and the gearbox (easiest good ground), but removing the negative terminal from the battery made it shoot down to near enough 0 ohms. Simply adding the battery to the equation changed the ground resistance. Removing/replacing the positive terminal did the same thing. Had no idea what was going on. Fiddled with it a bit and it seemed to stop doing it.

Ran around in circles for ages rechecking everything. Everything seemed to be good and I couldn't work out what was going wrong.

As a last resort I decided to figure out why I wasn't getting power for high speed rad fans. Low speed worked fine when the thermo switch was bridged but no high speed. I had no 12V at the FCM plugs for high speed rad fans. I was getting 12V out of the back of the fuse box on top of the battery so the fuse and fuse box was good.

I did some digging up the wire, pulling off tape and untwisting the loom. And I found this sucker:

I figured it couldn't hurt to fix it, especially when I noted that on my FCM pinout this wire was labelled as "Battery power for FCM". I assumed that it just powered the rad fan through a relay, but seeing as I was getting nowhere I went ahead and spliced in a new section of wire.

Started her up just to try it. AC WORKED. BOTH RAD FANS WORKED ON LOW SPEED.

I couldn't believe it. I noted this issue and put it on the back burner to resolve the "real problem". This was the real problem all along. I now have ice cold AC and working rad fans for the first time since I've owned the car.

I really hope these monologues can help another person in need out at some point.

Thanks for listening to me ramble.

 

[seaglf]

Fan speed

Fans should not come on with the key off. VW is crazy with their circuit logic - check the fuses.

I'm still waiting for someone to answer my question. I can turn my key ON but not start car, and both fans come on. But how do I know if they are on low or high speed?

 

[Genesis]

If they're running on high they're QUITE loud; it's rather obvious. If they're running but start sort of slowly then they're on low.

 

[seaglf]

If they're running on high they're QUITE loud; it's rather obvious. If they're running but start sort of slowly then they're on low.

Thanks for the response, but its not obvious to me since I don't have any reference to go by. Also I can't tell if its starting out slow because I'm in my car when I turn it on. Is there some way to test high and low speed, so I could have a reference. I do have a rosstech vag com.

 

[Genesis]

Open the hood and driver side window. Reach in from the outside by the driver side window with the hood open, A/C switch on and turn the key to ON while looking at the fans. If they're on high they're VERY loud.

If you turn OFF the A/C switch and turn on the ignition they should NOT run at all unless the coolant temp is very high.

If they switch on and off with the A/C switch (engine off, ignition on) odds are overwhelming they're running on low.

They run on high if (1) the A/C pressures are quite high (which can will happen in hot weather if the car isn't moving -- or is creeping along such as in stop and go traffic and there's no or nearly no airflow through the radiator and thus the low speed is insufficient) or (2) the thermoswitch in the radiator is closed, indicating excessive coolant temperature.

 

[DanG144]

There are some fan tests in post #1 of this thread. You can test the fan speeds by jumpering the radiator temperature switch.

It is obvious once your ear is trained, not obvious otherwise if fast or slow. This is a very common question.

Genesis, add the following, as well - if the AC refrigerant pressure sensor is failed the fans often run in fast. If your refrigerant pressure sensor (called a switch in much VW literature is leaking oil at the electrical plug it is almost certainly failed. Otherwise testing is as specified in post #1.

 

[wonneber]

Chased my tail for a good hour because I was reading 10 ohms between the negative battery terminal and the gearbox (easiest good ground), but removing the negative terminal from the battery made it shoot down to near enough 0 ohms. Simply adding the battery to the equation changed the ground resistance. Removing/replacing the positive terminal did the same thing. Had no idea what was going on.

This is why I am not a fan of resistance tests for higher current devices.
A voltage drop test should have shown more then a few tenths of a volt.

 

[CameraJack]

There are some fan tests in post #1 of this thread. You can test the fan speeds by jumpering the radiator temperature switch.

It is obvious once your ear is trained, not obvious otherwise if fast or slow. This is a very common question.

Genesis, add the following, as well - if the AC refrigerant pressure sensor is failed the fans often run in fast. If your refrigerant pressure sensor (called a switch in much VW literature is leaking oil at the electrical plug it is almost certainly failed. Otherwise testing is as specified in post #1.

I could be wrong but I believe earlier versions with four pins were a high/low pressure switch, and the later ones with three pins are pressure sensors.

 

[seaglf]

Open the hood and driver side window. Reach in from the outside by the driver side window with the hood open, A/C switch on and turn the key to ON while looking at the fans. If they're on high they're VERY loud.

If you turn OFF the A/C switch and turn on the ignition they should NOT run at all unless the coolant temp is very high.

If they switch on and off with the A/C switch (engine off, ignition on) odds are overwhelming they're running on low.

They run on high if (1) the A/C pressures are quite high (which can will happen in hot weather if the car isn't moving -- or is creeping along such as in stop and go traffic and there's no or nearly no airflow through the radiator and thus the low speed is insufficient) or (2) the thermoswitch in the radiator is closed, indicating excessive coolant temperature.

Thanks I'll check it again.

 

[seaglf]

There are some fan tests in post #1 of this thread. You can test the fan speeds by jumpering the radiator temperature switch.

It is obvious once your ear is trained, not obvious otherwise if fast or slow. This is a very common question.

Genesis, add the following, as well - if the AC refrigerant pressure sensor is failed the fans often run in fast. If your refrigerant pressure sensor (called a switch in much VW literature is leaking oil at the electrical plug it is almost certainly failed. Otherwise testing is as specified in post #1.

Thanks I will check it further, I believe there running fast. I also have been getting the high coolant signal code, even though I have changed to the green sensor. Someone told me it might be the ambient air sensor.

 

[Genesis]

Read here: There is a test for both high and low speed fan operation, so figuring out which you've got is easy.

http://pics.tdiclub.com/data/516/A4_Coolant_Fan_testing_Rev_7.pdf