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MK4 & MK5 Owner
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Discussion Starter #1
So I go to use my a/c today and it never turned on. I push the button, it lights up but no cold air. Blower is blowing good. Thing is I never heard the compressor kick on. Usually it makes my car idle high and vibrate like a sob. What should I be looking for? Not sure what fuses to check or relays. Kinda stumped.
 

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AC fuse is position 5 which is a 7.5amp and position 25 which is 25amp fuse.
Here's where I used to look at the fuse info for the MK4 Golf/Jetta IV Fuse List

See if the clutch is engaging. At idle with the AC off the center of your AC compressor pulley should not be moving.

Also, turn your AC on for a minute or so and touch the AC compressor, it should be cold to the touch if it's working.
 

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First thing I would do after fuses is check power to the compressor clutch.

Compressor clutch is a common problem on these. My A/C is out for this reason.
If the clutch doesn't engage then it's not going to kick the compressor and put noticeable strain on the motor.
Can check power on it right here.


And the DIY I stole it from. VWVortex.com - DIY - MKIV GTI, Golf, Jetta Compressor, TXV, Dryer
 

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MK4 & MK5 Owner
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Discussion Starter #4
Well I opened the hood and briefly checked it out. With the car running and the a/c button on my car idles normal the. Bumps up like its trying to kick on. Then goes back to normal, then again and so on. Also the rad fan is working just fine when the button is on. Going to see if I can see the clutch doing its thing.
 

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MK4 & MK5 Owner
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Crazy storm just rolled in. Knocked my grill over, patio table and chairs and ripped branches out of the tree. Heading inside for now.
 

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Measure the resistance across the 2 terminals of the compressor clutch coil. You should see about 4 ohms. If not, if you get 0 ohms, the clutch coil is shot. It can be replaced on the car without dumping the freon.
 

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Knows nothing about VWs
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Sounds like a vac leak. Weird. Car revs to get back to proper idle and over revs itself. Not sure how you a/c would cause it unless the compressor is trying to seized amd pulling too much current thus killing the engine. I am betting your voltage drops right before the rev happens.
 

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I wonder if the compressor is trying to kick on, and that's when the idle changes.
 

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That's the exact sound you will get when the compressor doesn't engage.

The ECM is raising the idle speed in anticipation of the compressor engaging. When the compressor doesn't engage, the ECM reverts back to the lower idle setting. It will continue to try to engage the compressor every few seconds.

See my post above. Check the resistance across the compressor clutch coil and let me know he results.
 

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Well I've been doing alot of reading on this problem, and numerous people say that the expansion valve is bad. I just went and bought it today from the local auto parts store (almost $40) and I am going to pick it up tomorrow afternoon. Hopefully this will fix my A/C.

My question is can I change this valve without losing any freon???
 

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Well I answered my own question by looking under the hood and finding this expansion valve. I will have to drain my system, change this valve, and recharge the system. I will probably grab my test light and check power to the compressor and then change this valve. I will give an update tomorrow on weather or not this fixed the problem
 
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