06 jetta ac problem (let's beat the dead horse some more)

Alright folks my Jetta had the typical problem of the AC taking several miles to get cold. I replaced the Refrigerant control valve (Usual problem) Now my AC won't come on at all even though I've charged it and the low pressure switch shouldn't be causing it to cut out.

So I tested the voltage to the RCV and it was jumping from 3v to 30vdc which is odd considering the car only has a 12v system. I guess the question is, would a bad fan control module cause this?

Does anyone know the typical range of the voltage to the RCV?

Have you scanned the car with VCDS? That would help finding the issue. Also you can test the functionality of the fans with VCDS. Are you sure that you have not under or over-charged the system? If the system is undercharged, you will get a G65 sensor pressure error. If the system is over-charged, you will also get an error, and the AC will not come on.

I’m going thru a similar issue with my ’06 Jetta TDI. I first thought that the system was needing more 134a so I bought a can and added to the system. However, the system started shutting down almost as soon as I started it. I bled some Freon off and the system started working again but didn’t fix my problem. It seems that the system was over charged and causing the overpressure switch to stop the compressor. My problem ended up being a blend motor in the under dash system.
My suggestion is to borrow or rent a set of AC gauges and see what your system is doing. You will be able to see the low and high pressures to compare to factory spec’s .
JMHO, Steve.

^^thats some good advise.
With the availability of can-with a single gauge R134A itsneasy to overfill.
The beast way to load the right qty is to evacuate refrigerant (not dump into atmosphere) vacuum it, amd charge the system using a scale following the car manifacturing specs and use the high and low side gauges to confirm system behavior.

However those magic single gauge R134A are optimistic at best. In the hands of the layman with no training or tools can make your AC problem harder to diagnose.

On my 06 jettat tdi, probably all the jettas, there isnt a straight 12volts open/close. Its a pwm ( pulse width modulation) signal. With a test light you will find one wire has a constant 12 volts. The other wire is pulsed at around 4 pulses a second by going to ground to energize the solenoid. The length of time of each ground ' pulse' determines how much refigerant flows. The right way to check it is with a scope. But i could see i was getting some sort of rapid ground pulses by putting one lead of my Fluke DMM on the ground signal wire and other to ground post of battery with continuity check selected.......and got a rapid beep-beep-beep.

Compressor turn-on pressure for 06 Jetta TDI?

I think i now have the correct RCV valve from Polar Bear. Will install and then re-attempt to charge the system.The first attempt didnt work, as I think I really had the wrong RCV valve. Kept adding in more and more r134a, but the compressor never turned on even when when low side went above 100 psi. If the compressor still refuses to run, i really dont want to subject the compressor to such high low side pressure again. So when i start charging th low side, at what pressure should low side ptessure zwitch activate and start compressor running?

jimigunne said:

I think i now have the correct RCV valve from Polar Bear. Will install and then re-attempt to charge the system.The first attempt didnt work, as I think I really had the wrong RCV valve. Kept adding in more and more r134a, but the compressor never turned on even when when low side went above 100 psi. If the compressor still refuses to run, i really dont want to subject the compressor to such high low side pressure again. So when i start charging th low side, at what pressure should low side ptessure zwitch activate and start compressor running?

Click to expand...

How are you recovering and charging your refrigerant?

banshee365 said:

How are you recovering and charging your refrigerant?

Click to expand...

Now with a robinair unit. I installed the new rcv from polar bear. This was an exact match for the bolt-on, pig tail style rcv that was installed on the car. Matched it up by the pics on their web page. The lady at Polar bear said that the pig-tail style is aftermarket, not oem! So it was replaced before i bought car at 180K. i also replaced the smaller ac fan....found it bad, read open circuit for ohms check.also the receiver dryer was replaced, but not expansion valve or compressor. Its a Sanden. But it was working with a discarge temp of 43 deg. It just would sometime take 30 minute (driving) before compressor would kick in and start cooling. So this second attempt with a second rcv from polar bear has had a similar result. On recharge only about 8 oz went in and the low side hit 100 psi while the high was 85. Blower on high, temp set to min, ac control switch on(and light illuminated. Car idling
. so i shut off recharge attempt at that point. Compressor is still not turning on. I checked car while idling with vcds. Auto hvac. Show no malfunctions, no codes. (Its the Climatic. Control, not climatronic). Neither engine fan or ac fan ever cycled. But engine heat stayed normal, and i understand the ac fan doesnt run until pressure hits 130, and it never went over 85. Seems like the compressor seals on rotary vanes are not destroyed....would not the low and high sides equalize pretty quick if compressor was shot?
Now i read on another thread that vcds can run a test on the ac hvac system and it teports back shut-down codes. This is what i need to do, but i didnt see this system test option in vcds. ( I just ran the test for all controllers.) Have to search for the manual on this diagnostic test.... or better yet a video primer.
I really dont want to spend the 250.00 or so for a reman compressor on this car since its got 280k miles on it! Thanks!

Another thought. I could connect my scope up to the hi/low wires going to the rcv and look at signal. What is the signal when in shut-off mode vs signal for max cooling? Probably nobody in forum knows?

Heres a great start...

You cant use the typical high/low pressure gauge sets to diagnose these systems or any R134 systems...

After powering on the AC CHECK the AC fan(small one) to see if its turning, if not replace it.

You have to evacuate/recover the Freon, vacuum the system for 10-15 minutes and weigh in 18.5 ozs of R134 Freon. This is just the minimum required work to get it where you can diagnose the system.

To even try to diagnose/work on these systems would be futile.

The electronic valve is going to be partly open and mess with your gauge pressures anyway.

If anyone can get the charge to the correct without doing this, I am all open ears...I live in Texas and would love to know..

Mach1 said:

Heres a great start...

You cant use the typical high/low pressure gauge sets to diagnose these systems or any R134 systems...

After powering on the AC CHECK the AC fan(small one) to see if its turning, if not replace it.

You have to evacuate/recover the Freon, vacuum the system for 10-15 minutes and weigh in 18.5 ozs of R134 Freon. This is just the minimum required work to get it where you can diagnose the system.

To even try to diagnose/work on these systems would be futile.

The electronic valve is going to be partly open and mess with your gauge pressures anyway.

If anyone can get the charge to the correct without doing this, I am all open ears...I live in Texas and would love to know..

Click to expand...

As i said: the system was evacuated and held 29 in. all day! i only got maybe half the first can (6 OZ.) in on a second attempt to charge system (and with a new/ correct solenoid valve from Polar Bear) and the compressor never turned on. The low side pressure reached about 100 psi and climbing. Car running, ac selected ON and max cold. Registers still blowing 100 deg air. So i stopped the recharge attempt.
I am not real experienced with this, but I am sure the low press switch should have activated the system at a much lower press than that. There was nothing wrong with it, so i am sure it did, and something else prevented the compressor from running. If it had started running, the pressure should not have been going up so much higher than normal pressure. Because 35 to 45 psi is normal for this car. As i said, i initially had about 40 deg discharge air.....the only issue i with the ac was that sometimes the ac was blowing ambient for 30 minutes before it would cool. Now am having to drive car with NO ac! I know i have a signal to the new solenoid valve, but dont have any info on how to analyze the pwm signal to see if its correct. I dont see that i could have done something to block the refrigerant loop. i replaced the receiver/dryer. Unless the expansion valve just happened to become blocked? Its a huge job to replace expansion valve. And i dont want to spend another 250.00 or so to try a new compressor, only to find that it still doesnt work. Any ideas?