AC not working

For the life of me, I can't get the search to work. Or I wouldn't be asking for help.

Anyways, last year my ac had stopped working. It was basically the last hot day we had. So I figured I'd look into it later. Well long story short, it's time to fix it. The rad fans do not come on unless the AC button is pressed. The button lights up and all cabin fan speeds work. And all speeds blow air. The in cab fuse is good, as well as the under hood green fuse. I'm thinking it's the fcm. But wondering why the fans both work when the AC button is on, but not when the button isn't on. The clutch is not engaging. AC port gauge shows past safe. I assume that is because it isn't being circulated. Any help as always is greatly appreciated.

The fans are used to help cool the Freon from a high pressure gas to a high pressure liquid so when the A/C switch is on....then those fans come on.
The only other way those fans come on is when the temp switch in the RAD tells them to come on given a certain coolant temp, low speed for on temp,and high speed for the higher temp....don’t remember what the temps are but I think the low speed is 208-212f and the high is around 220 f or there abouts.

Also check to see if you have 10-12 volts at the compressor connector, if yes then see what the resistance is across the coil, see if it’s open, normal should be about 3-4 ohms.

Understood. Is there anything else I can test as to why the AC clutch isn't working?

I checked voltage at the clutch and have 9.3 volts at the compressor plug. Car running or not and with the AC button on and with it off

I checked resistance at the coil. Either my meter is acting up, or the coil is bad. It's giving me no reading at all

Then the coil is open and bad.

If you touch the meter leads together do you get zero or there abouts? If yes. Then meter is good.
Make sure that you are touching the contacts on the connector and recheck the readings, if still funky or no readings then bad coil.

9755 said:

I checked resistance at the coil. Either my meter is acting up, or the coil is bad. It's giving me no reading at all

Click to expand...

Touch the meter leads together.
The needle should move or if it's digital the numbers should change.

How old is the battery in it?

I will double check the numbers this afternoon. The battery is a little over a year old

If the coil is reading open it's bad; it should read ~4 ohms or so. Very common failure on these vehicles; it can be replaced on-car. It's a bit tricky to get right but not horrid and materially cheaper and easier than replacing the compressor (which requires recovery of the refrigerant, etc.)

Any specific brand or place recommendations for the coil?

I have been buying my parts from ID-Parts. https://www.idparts.com
Good stuff.

I agree. I get 99% of our stuff from them and kerma. Unfortunately I can't find the AC clutch or coil on idparts

9755 said:

I agree. I get 99% of our stuff from them and kerma. Unfortunately I can't find the AC clutch or coil on idparts

Click to expand...

Contact ID Parts and ask. They are very helpful. Parts like that are a bit specialized and there is a lot of junk out there.

you should be able to find a clutch but this is what i did for my 01 Passat. - it had the exact failure - open circuit on the clutch for which my local mechanic of course quoted many hundreds and hundreds of dollars because they wanted to replace the entire compressor. They, of course didn't mention the open circuit.

I went to Ebay and found the worst looking (hence cheapest) compressor I could find and I bought that.

I took the clutch off that used compressor which also gave me some practice and a good idea of what the job would be like on the car.

compressor goes into the recycling bin.

Guys I’ll piggyback. Same scenario as above except replaced the fuse panel about a year and a half ago due to corrosion. Fuses good. Connected a bottle and pressure was in the red zone. Fans DO come on when ac is pressed and blower on. Voltage lead to compressor is 9 volts and resistance on the compressor side is 3.8 ohms

Mkivbren, you really should start your own thread with a link to this one stating same issues, otherwise some confusion will occur.

Yours seems to have correct resistance at the coil and you appear to have voltage, the OP does not have resistance as his appears to be open.

Every AC diagnosis thread needs this link. The PDF linked in the thread is excellent:


http://forums.tdiclub.com/showthread.php?t=242699

csstevej said:

Mkivbren, you really should start your own thread with a link to this one stating same issues, otherwise some confusion will occur.

Yours seems to have correct resistance at the coil and you appear to have voltage, the OP does not have resistance as his appears to be open.

Click to expand...

..Or present both scenarios in one place?

300D said:

Every AC diagnosis thread needs this link. The PDF linked in the thread is excellent:


http://forums.tdiclub.com/showthread.php?t=242699

Click to expand...

Thanks!

Oh, and the best way to search these forums is to run a constrained Google search.

Type your search words, followed by “site:forums.tdiclub.com”. This will force google to look only at the forums on tdiclub. The forum’ search function doesn’t work all that well.

Example, if I were searching for info about the T14 connector at the fan control module I would type into Google the following string:

T14 fan control module site:forums.tdiclub.com

mkivbren said:

Guys I’ll piggyback. Same scenario as above except replaced the fuse panel about a year and a half ago due to corrosion. Fuses good. Connected a bottle and pressure was in the red zone. Fans DO come on when ac is pressed and blower on. Voltage lead to compressor is 9 volts and resistance on the compressor side is 3.8 ohms

Click to expand...

As a follow up, my issue was the original compressor, as suspected.