Basic AC questions

My 2000 Golf TDI no longer has AC. It was working marginally until last week when it was really hot. Now nothing. It doesn't come on at all. Both fans are running. I checked the power to the compressor and it just comes on and off immediately every second or so. I believe that means that it has no charge left.

I bought the Redtek kit at Canadian Tire and now I need basic instructions. There is a snap-on connection to the low pressure fitting on the AC. I did manage to get it on but it was not easy. The gauge still read zero psi. I took this to mean that the AC system was indeed empty. But when I opened up the can of coolant it went up to 100 psi quickly. From this I take it that the low pressure valve on the AC is not working and needs to be replaced. Or am I doing something totally wrong? I tried gently pushing on the pin in the AC valve but it didn't seem to want to budge. Is there still coolant in the system? It seems highly unlikely.

Any help is appreciated.

Last time I checked, one of those redtek cans is about 6oz, and your system takes about 800g, meaning that to fill an empty system, you will need to charge it with 4-5 of redtek.

An empty system will have 0 psi, but if it was functioning marginally last week, I doubt it was completely empty.

When you got the redtek charging hose/gauge to attach to the low-side fitting, did you turn the knob (the one on the hose fitting, not the one attached to the can)?

was there any appreciable change in the gauge when you did so?

You saiud that the gauge went to 100psi. What did you do to make that happen? turn the screw/knob on the can? how many turns in? how many turns out?

I think you have already determined that the problem is not with the parts of the system that don't require evacuating and recharging the system. Time to call in the experts. An incorrect amount of refrigerant in the system can do a lot of damage, and you don't have any way of establishing this. Take it to a shop, tell 'em to fix it.

I think the redtek is more efficient so less is required, maybe 2 cans. The instructions say to fill it until the low pressure side reaches a certain pressure.

My setup doesn't have a valve on the hose fitting. When I attached the hose fitting, nothing happened. There is the hose fitting, a fancy gauge, and the connection to the can.

The gauge went to 100 psi when I turned in the screw and it pierced the can. Thus I have concluded that there is something wrong with the hose fitting on the low pressure connection.

GoFaster said:

I think you have already determined that the problem is not with the parts of the system that don't require evacuating and recharging the system. Time to call in the experts. An incorrect amount of refrigerant in the system can do a lot of damage, and you don't have any way of establishing this. Take it to a shop, tell 'em to fix it.

Click to expand...

That's too easy. I bought a VW so that I could learn about these things.

If you go to the RedTek website, there you can look up the equivalent of their product to R134a. I was informed that the capcity of the system in the TDI is 25oz. I think I was also told that the sticker under the hood should have that info.
One can of 6 oz Redtek is the equivalent of 18 oz of R134a.


Also YOUR system needs to be totally void of R134a, RedTek and R134a DO NOT MIX!!!

RED TEK® 12a Hydrocarbon Refrigerant
Replaces R 12, R 134a 301 12a 6 oz. Can (18 oz. equivalent)



Also some info from PartSource

The coupling for the low pressure service port was a very tight fit. I had to use some oil for lubrication and channel lock pliers to get it on. Turns out I do have pressure (80psi), so the problem is with the electronics. Maybe switches? I have had some funny readings on the temperature gauge, but not sure if that is part of the AC system.

Seems to be the compressor clutch. I believe that I put 12 volts to it and nothing. It is hard to get into those connectors, to be sure. Also I measured the resistance and it appeared to be inf. Is it safe to assume that the compressor itself is okay? Or best to replace the whole thing?

Looks like the sources of the clutch (perhaps just the coil) are ebay or a used compressor with clutch. Anyone have luck buying on ebay?

hmm... it should not be a tight fit as such unless we have very different hoses.

Are you sure you were at the low pressure side?
On an ALH engine it is just infront of the Injection pump and a little to the left I believe.
You should be able to pull up on the metal fitting of the hose and push down quite easy to fit it in place, then release the fitting to lock it in.
make sure the can is on the other end though, and the handle fully unscrewed to not puncture the can.
Those gauges on the hose seem to be iffy btw.
Turn your A/C system to max when filling.
Then screw it down completely on the can side, then unscrew to release refridgerant.
Make sure can was pre-shaken, also shake gently as it's releasing. Make sure you hold can upside down, so hose would be pointing down toward
the car, and bottom of can up.

However, you seem to think it is not a leak issue.
If it is a leak though, make sure you have a DRYER can to remove the moisture from the system after it is charged, and then a SEALANT can to seal the system.
Good luck.

Re the compressor clutch:

In your first post, you stated that the power to the compressor is going on and off every second or so (it is not supposed to be like this, by the way). You have now said that you put 12 volts to the compressor clutch and "nothing".

When the compressor clutch is disengaged, the outer (pulley) part is supposed to spin with the engine and belt, and the inner (shaft) part stays stopped. When the clutch engages, the whole deal is supposed to spin with the pulley. What's yours do?

sidshock said:

hmm... it should not be a tight fit as such unless we have very different hoses.

Are you sure you were at the low pressure side?
On an ALH engine it is just infront of the Injection pump and a little to the left I believe.
You should be able to pull up on the metal fitting of the hose and push down quite easy to fit it in place, then release the fitting to lock it in.
Good luck.

Click to expand...

The low pressure and high pressure fittings are different and I had it on the low pressure one. Perhaps new fitting, tolerances, dry, made in China, Canadian Tire, other? It went on fine with channel lock pliers and some force. Sure didn't leak!

GoFaster said:

Re the compressor clutch:

In your first post, you stated that the power to the compressor is going on and off every second or so (it is not supposed to be like this, by the way). You have now said that you put 12 volts to the compressor clutch and "nothing".

When the compressor clutch is disengaged, the outer (pulley) part is supposed to spin with the engine and belt, and the inner (shaft) part stays stopped. When the clutch engages, the whole deal is supposed to spin with the pulley. What's yours do?

Click to expand...

I was able to turn the compressor by hand; no binding or sounds. The coil is open circuit and doesn't respond to power.

Hopefully, the cycling is happening because the clutch isn't engaging and the pressure switch is turning it off. Otherwise, I will have more trouble-shooting to do.

I found just the coil on ebay; just needs the wiring spliced, for less than $50. So will try that first.

Reporting on this problem. Removed the serpentine belt and pryed down the compressor. My snap ring pliers were too fat to fit into the space, so had to disassemble it and use the gripping part with separate pliers and vice grips to remove them. There was quite a bit of rust in the clutch itself which I removed somewhat. Installed the new coil, re-assembled and it seems to be working! Don't know for how long. But I learned enough to get cool air for now.

Your compressor clutch failed and the system is probably still fully charged. Same thing happened to me 4 years ago. Bought a used VW compressor, pulled the cluch and replaced it on to the original comrpessor while it was still on the car and has been fine ever since. A new AC cluthc at the dealer is around $500.

imo000, would you be able to have a look at mine and see if it's the same problem some time. I ran half the summer last year without the AC cause I couldn't figure it out and I didn't want to bring it to the StealerShip.

Any help would be appreciated. I work in Kitchener and live in Acton so anyone in between or at both ends would be great.

Payment is BEERS

Brian B said:

imo000, would you be able to have a look at mine and see if it's the same problem some time. I ran half the summer last year without the AC cause I couldn't figure it out and I didn't want to bring it to the StealerShip.

Any help would be appreciated. I work in Kitchener and live in Acton so anyone in between or at both ends would be great.

Payment is BEERS

Click to expand...

Sure no problem but if you could take the belly pan off before coming, that would make things a heck of a lot easier to check. However checking the AC clutch is very easy. Pull the electrical connector apart, start the car and turn the AC on. If there is +12V at the connector, your clutch is gone. If there isn't then the clutch is ok. Send me a PM and we'll set something up.

Us TDIs have it easy, on the 1.8T the compressor is where the alternator is. Took me 8hrs to change my neighbours AC clutch, with the compressor bolted onto the engine. Had to make custom snap ring pliers and all this working from a mirror.

I found this thread over at vwvortex to be helpful, although it was to replace the entire compressor and clean the A/C system.

http://forums.vwvortex.com/zeropost?cmd=tshow&id=3244824

Here's the drawing of the clutch:


I only replaced item 43, the coil, obtained on Ebay at a good price. No need to open up the A/C system!