AC question

[300D]

Last summer I just about completely rebuilt my AC. New compressor, new condenser, new Fan Control Module, new drier, new expansion valve. Seemingly all good parts from AutoHausAZ. Compressor is a Nissens. Early this summer I discovered it not working again. Thought that maybe it was a leak at the drier. I really struggled getting good access at that point to get a good feeling tight connection. I pulled out my gauges and discovered that the pressures are good. Did the fan test, and both fans are coming on. Checked the pressure switch duty cycle and it was within spec. Checked all the fuses and they are all good. Pulled apart the fuse connector on top of the battery and there is no corrosion under there. Tested the power at the compressor plug. The AC troubleshooting guide says that there should be 9-9.5 volts at the connector, but I got something a wee bit different. First I tested unplugged with car running and AC on and I got 10.5V. Then I tested it again with the car running, but with it plugged in and I got about 11.6V with the AC system switched off, and 12V with the system switched on. Throughout all this, compressor clutch is not engaging. I am about to give up and bring it to a respected VW mechanic, but figured I would check in here first. Although I have not tested resistance yet on the compressor plug, my feeling is the Nissens compressor's clutch is the culprit.

What do people think? Do I need to go through the rest of the troubleshoot? Or have I narrowed it down to a faulty compressor clutch? It just kills me to think that I have all new bits in there and maybe one of them has already failed.

Oddly enough, the car's idle does just barely drop when turning on the AC. I am chalking this up to the fans coming on and adding load to the alternator.

 

[Zak99b5]

Ohm out the clutch. Should be like 3-5 iirc. You could also feed it direct battery voltage to see if it clicks (I’d do both, but I’m a belt and suspenders kinda guy).
Clutch can be replaced with compressor still connected to the lines. $40 for a new one (at least for the sanden compressor).

 

[csstevej]

^^^^ what he said ^^^^

 

[oilhammer]

You may have a bad clutch, Nissens is not the first (or second, or third...) choice I would make for an ALH. You may find it has no replacement clutch available, and you'll just have to buy the whole thing.

FWIW, the voltage on the plug to the clutch coming from the FCM will spike to a high(er) amount, maybe 11-12v, then settle back down to around 6-8v. That's because it takes more 'oomph' to pull the clutch in, but not much to hold it there. Some test lights will simply "flash" once when doing this test.

 

[300D]

Alright, I will stick the OHM meter on there. And here I thought I was buying up the scale a wee bit with the Nissens. That is super annoying. I am a pay more to buy it just once kind of guy.

Oilhammer, what is your first and second choice? OEM I imagine, and then?

Thanks.

 

[P2B]

Oddly enough, the car's idle does just barely drop when turning on the AC. I am chalking this up to the fans coming on and adding load to the alternator.

In my experience the fans do not draw enough current to affect idle, but fans plus compressor will make the tacho needle dip momentarily at switch on. I suspect your clutch coil will ohm out as good.

 

[300D]

The compressor is not turning on in anyway whatsoever. It might be trying to turn on and creating a draw. But the rpm dip is very very slight. Probably shouldn’t have mentioned it. Way less than when it actually turns on.

 

[oilhammer]

Sanden is the OEM supplier for these, that would be my first choice. Second would be a Denso (which these are often just a restickered Sanden anyway), then a Valeo, then Behr.

 

[300D]

Thanks for the recs, Oilhammer.

I almost just pulled the trigger and ordered a Sanden, but first I figured I would get down under the car for some quick tests, and there is definitely some weird electrical stuff going on.

First up, I put the test leads on the compressor electrical receptacle to test resistance. I was always under the impression that it didn't matter which lead went where for resistance. But, I found no continuity when black tester lead was put to the pin that leads to the black wire on the compressor, and 6.75 ohms when red tester lead was put to the black wire.

Secondly, and also a clear problem is that the plug going to the compressor has power at all times. Even with the key off and removed. Odd.

This sent me back to the troubleshooting PDF, and this is confirmed with finding power at T14/9(connector at the Fan Control Module) at all times. This is supposed to be switched with the key. Fun.

Finally, T14/6 is supposed to be a good ground with about 0.5 ohm resistance. With the car running this ground had 23.1 ohms resistance. So, I took apart the battery tray and got down in there and lo and behold everything looked fine, and T14/6 now had good continuity to ground.

I think I have reached the limit of my pay grade.

 

[P2B]

I was always under the impression that it didn't matter which lead went where for resistance.

That is correct

But, I found no continuity when black tester lead was put to the pin that leads to the black wire on the compressor, and 6.75 ohms when red tester lead was put to the black wire.

One reading is spurious. The 6.75 reading is probably correct, which means the clutch coil is good.

I would describe the rpm dip when a fully functional AC system turns on as very brief and very slight.

 

[Zak99b5]

Just to confirm the coil for the clutch, jumper battery voltage to it and see if it engages or not. Belt AND suspenders lol.

 

[csstevej]

That or just ohm it out with a meter….should be around 3-5 ohms.

 

[300D]

Going to start with getting all the pins in T14 to read correctly. Will post results of my wire chasing.

 

[300D]

Update: I had my VW guy go through the electrical gremlins. He sorted a suspect ground, but also determined with 1000% certainty that the servo on the compressor clutch is dead. He is going to put in a new Denso compressor. He couldn't get quick access to a Sanden, and ordering one was going to take 2 weeks. I am having him do it so that this one will be warrantied. AutoHausAZ, where I got the Nissens, has a great parts warranty, but only applies to compressors when there is a purchase order for 'professional installation'. It's nice having a quality VW mechanic when I run out of steam working through something a second time...

 

[csstevej]

What is “ the servo on the compressor clutch “?

 

[300D]

Its the little motor that when powered makes the compressor’s clutch engage.

 

[csstevej]

Unless you have something different on your 03 , there is no servo for the clutch. It’s just two wires to the clutch electro magnet on the A/C.

 

[300D]

Unless you have something different on your 03 , there is no servo for the clutch. It’s just two wires to the clutch electro magnet on the A/C.

Then it is that that is bad. Didn’t use the right terminology. The thing that activates the clutch. Not a servo. An electro magnet.

 

[csstevej]

Ahh ok then.

 

[300D]

Sorry about that, my bad. A million different projects on the brain at the moment. Hence the taking it to the mechanic part...

 

[csstevej]

Lol I truly understand that.

 

[BobnOH]

Servo is a general term sometimes referenced to a specific device, like actuator or controller. Merriam Webster defines it as a Servomotor or Servomechinism. So the clutch electro magnet is a servomechanism. Semantics, always good to watch your language.

 

[P2B]

You need a compressor clutch coil. It can be replaced for a lot less money than replacing the entire compressor, and you do not need to evacuate and replace refrigerant.

 

[300D]

You need a compressor clutch coil. It can be replaced for a lot less money than replacing the entire compressor, and you do not need to evacuate and replace refrigerant.

Unfortunately there is not one available for this compressor.

 

[ToxicDoc]

Unfortunately there is not one available for this compressor.

Check this one if it matches

2003 Volkswagen Jetta TDI Sedan 4-Door 1.9L A/C Compressor Clutch (GG554-CL)

2003 Volkswagen Jetta TDI Sedan 4-Door 1.9L

www.rycompressors.com

 

[P2B]

Unfortunately there is not one available for this compressor.

Definitely available for Sanden, what brand is yours?

 

[300D]

Definitely available for Sanden, what brand is yours?

As discussed earlier in the thread, a Nissens.

 

[300D]

Update. All is now good in the world of AC. My excellent VW mechanic (Kyle Bergey at Berg-Werks in Appleton, ME) popped in a new drier and new Denso compressor this morning. He doesn't do refrigerant so I took it home, pulled a vacuum, and then did a refrigerant fill up myself. After putting in 750g of fresh and shiny R134a as called for on the sticker under the hood, the system is now working perfectly once again.

Thanks to all for your input. Much appreciated as always.

 

[BobnOH]

Nice work!

 

[pkhoury]

Sanden is the OEM supplier for these, that would be my first choice. Second would be a Denso (which these are often just a restickered Sanden anyway), then a Valeo, then Behr.

Just what I was looking for. The other Brian, @alphaseinor , keeps telling me to buy a Sanden, but I can't justify spending over $600 for it. I don't want to do the job twice, but I decided I'll be redoing my whole AC system in my 2000 Golf, reusing some lines, but running AC flush just to be safe.