A/C Problem - No output power to compressor clutch

So I just got this car, and am in the midst of getting everything properly operational. The AC is the ticket now with rising ambient temperatures.

I replaced the FCM straight off the bat because I heard how they are often the culprit. Everything appears to be fine except for two things; my compressor coil reads open on a ohms test.. and it doesn't receive its 9-9.5v signal.

I found a chart of the T14's pin out (not a picture mind you of the pin layout) and what each does, but i don't think its correct for my car anyway. I have battery voltage on a pin the chart says is unused for one thing, and battery voltage on other pins that i think should be other pins according to the chart.

I found what appears to be t10 as having continuity to the compressor from the T14 plug, so thats in order. I also found a myriad of battery voltage pins, but they didn't necessarily line up the charts pin out.

With the KEY ON and AC ON, we have the AC light on and both fans running on LOW speed. There is no output to the compressor.

---EDIT--- upon writing this and doing more research I found a pinout picture!

T13 shows on the chart as engine overheat signal from ECT, in my connector this pin fluctuates between 10v, drops a little to like 7v and then drops to 5v and back up to 10v in a completely steady rhythm of voltage fluctuation. Is this what a duty cycle sensor looks like to an analog voltmeter??

I am pretty sure I read that if the fans are coming on, then the OUTPUT for making the AC run is correct??

does the clutch work? monitor things in vag com. it will show a direction.

You no read? LOL

No, the clutch does not work, its coil reads open. HOWEVER, I still havent any voltage leaving the FCM to go to the compressor clutch.

I didn't think you could do anything in regards to the 01/vag com/air conditioning system. I'll have a look see here this evening.

SIDE NOTE ---

I now have an odd thing that hasn't happened in my 4 months of driving it.. the rad fans will just come on when i turn the key on (stone cold, no AC selected) and not shut off with the key. I haven't sat around long enough to see if they go off by themselves, but pulling their 30a fuse above the battery will shut them off and not restart them when you reinsert the fuse.. weird.

Check fuse #16 for you fan issue.

This connector is attached to the bundle of wires on top of your starter. The broken one in my picture runs the ac compressor.

Tdijarhead said:

Check fuse #16 for you fan issue.

This connector is attached to the bundle of wires on top of your starter. The broken one in my picture runs the ac compressor.

Click to expand...

Could you expand on this please? What specific issues were you experiencing? I am having similar difficulties.

8v-of-fury said:

So I just got this car, and am in the midst of getting everything properly operational. The AC is the ticket now with rising ambient temperatures.
I replaced the FCM straight off the bat because I heard how they are often the culprit. Everything appears to be fine except for two things; my compressor coil reads open on a ohms test.. and it doesn't receive its 9-9.5v signal.
I found a chart of the T14's pin out (not a picture mind you of the pin layout) and what each does, but i don't think its correct for my car anyway. I have battery voltage on a pin the chart says is unused for one thing, and battery voltage on other pins that i think should be other pins according to the chart.
I found what appears to be t10 as having continuity to the compressor from the T14 plug, so thats in order. I also found a myriad of battery voltage pins, but they didn't necessarily line up the charts pin out.
With the KEY ON and AC ON, we have the AC light on and both fans running on LOW speed. There is no output to the compressor.
---EDIT--- upon writing this and doing more research I found a pinout picture!
T13 shows on the chart as engine overheat signal from ECT, in my connector this pin fluctuates between 10v, drops a little to like 7v and then drops to 5v and back up to 10v in a completely steady rhythm of voltage fluctuation. Is this what a duty cycle sensor looks like to an analog voltmeter??
I am pretty sure I read that if the fans are coming on, then the OUTPUT for making the AC run is correct??

Click to expand...

What issues were you experiencing prior to replacing the FCM? Again, I am experiencing similar issues.

well if your clutch doesnt ohlm out where it should. open or short. i would think that is bad. check your fuses.

8v-of-fury said:

You no read? LOL

No, the clutch does not work, its coil reads open. HOWEVER, I still havent any voltage leaving the FCM to go to the compressor clutch.

I didn't think you could do anything in regards to the 01/vag com/air conditioning system. I'll have a look see here this evening.

SIDE NOTE ---

I now have an odd thing that hasn't happened in my 4 months of driving it.. the rad fans will just come on when i turn the key on (stone cold, no AC selected) and not shut off with the key. I haven't sat around long enough to see if they go off by themselves, but pulling their 30a fuse above the battery will shut them off and not restart them when you reinsert the fuse.. weird.

Click to expand...

what i was getting at is can you directly power the clutch to get the pump working. but if its open. the computer probably sensed this and shut off the a/c till the code was cleared. just as my car has a bad kessy antenna. when i try to open the hatch without unlocking it first it senses the bad sensor and shuts the exterior kessy off. Making it not lock or unlock by touching the door handle. But if i clear the code the front doors work as intended. No need to insult just because we are not on the same wavelength.

DivineChaos said:

well if your clutch doesnt ohlm out where it should. open or short. i would think that is bad. check your fuses.

Click to expand...

A little confused. As stated, my A/C clutch reads 4.1 ohms which is commensurate with just about everything that I have read. Additionally, as stated, fuses are good.

Fuses 5, 16, and 25 are all good.

01m_jetta_02 said:

A little confused. As stated, my A/C clutch reads 4.1 ohms which is commensurate with just about everything that I have read. Additionally, as stated, fuses are good.
Fuses 5, 16, and 25 are all good.

Click to expand...

can you read in vag com that the computer is actually energizing the clutch? would start by making sure the switch outputs the on signal to the computer. then the computer outputs the signal to the clutch checked by back probing at the computer. and beyond that. have you checked the pressure of the system? if the pressure is too low it will not allow it to activate. also if the pressure switch is bad... Do you have vag com? also i got confused with the thread jack. the op said his clutch read open. you never stated anything of the like.

01m, the thread jack you have started here has made it confusing to help either of us lol.

The clutch ohms out as open, my ac switch lights up and commands the fans on at low speed. I will try and see if I can back probe the fcm while it is plugged in and operational.

I have a hunch, I think my after running fans may be linked to a false overheat? Hmm, but I think that would command high speed fans.. it does run them about ten minutes, I hung around and waited to see what would happen the other night.

Power and ground at the pump will not make the clutch pull in no.

Ps. Sorry you were insulted, I wasnt meaning for it to be that way at all.

That picture I posted above shows a broken wire. The #4 wire as listed on the connector, if you look closely. That wire supplies power to the ac clutch. Check that wire and also the wire in the #3 slot which also goes to the ac compressor.

Tdijarhead said:

That picture I posted above shows a broken wire. The #4 wire as listed on the connector, if you look closely. That wire supplies power to the ac clutch. Check that wire and also the wire in the #3 slot which also goes to the ac compressor.

Click to expand...

well i would fix that wire first. you can temporarily cut and splice on both sides of connector. if that fixes it. you can repair the wire however you like. But if your clutch ohlms at zero directly at the compressor connector. might also have a bad clutch. and i think 8v (i mean 01m) got confused and thought it was his own thread.

DivineChaos said:

and i think 8v got confused and thought it was his own thread.

Click to expand...

It is his own thread, and he has a bad coil on his a/c compressor.

Tdijarhead said:

Check fuse #16 for you fan issue.

Click to expand...

Fuse 16 was good when I originally started messing around.. but it was blown. What a pain in my ass lol.

I have all the proper 12v inputs to the fcm. Ambient temp switch is proper, however the T10 of the 14 pin plug is sending out only 4.5v to the compressor.. but it is happening at all times.. even with the ac switch off and key off as well.

Ps. I literally hate this over complicated ecm controlled ac system.. lol

csstevej said:

It is his own thread, and he has a bad coil on his a/c compressor.

Click to expand...

Yes, loool and I know I must replace the coil, i have one on order. I am trying to diagnose the rest of the system in the mean time.

I didn't mean to thread jack. The issues were pretty close and were both entitled in a similar manner. Probably posted while looking at both threads at the same time. My issue is done.

meant 01m and not 8v. dangit. lol

csstevej said:

It is his own thread, and he has a bad coil on his a/c compressor.

Click to expand...

your right. was talking about 01m. whoops

8v-of-fury said:

Yes, loool and I know I must replace the coil, i have one on order. I am trying to diagnose the rest of the system in the mean time.

Click to expand...

well, it may be only sending part voltage looking for the resistance of the circuit. waiting to see if it sees current draw. not sure how they work.

I have read I should be seeing no lower than 9v.

From what I have read as well, the fact there is output on T10 and the fans are on. The pressure switches and such are reporting back "OK".

Well as it would turn out, the 4.33v I was seeing at the compressor wiring was indeed enough to suck the new coil in.. WEIRD. Upon dropping the compressor to remove the clutch, pulley and old coil.. it seems my nut came loose at some point and beat the splines off the clutch. No big deal! booger welds from a $90 mig to the rescue lol.

So after fixing that (albeit permanently lol) the system was working as it should, SCORE.

I got some gauges on it, and they were more or less fine. This was at 90f;



So I had some cans of the KwikKool and I decided to add one slowly to see what it would do. It worked incredibly!