Help: AC not working

[GMC_2002_Dmax]

My brother and I are stumped, my son's VW-GTI had ice cold air last summer and fall, sometime over the winter the compressor clutch went bad so I attempted to swap just the clutch out in the car, couldn't get it off in the car so I had the system discharged, I pulled the compressor out, swapped clutch assembly and re-installed within a few hours and pulled a vacuum down but it would not go under 24" of vac so I picked up new O-Rings for the suction and discharge side of the compressor and then it pulled down fine to almost 30" of vac.

Also while the compressor was out I drained/flushed and refilled with the proper PAG100 oil, reinstalled everything and we charged the system.

Started the car, pressures are equalized while the compressor if off, compressor running low side drops to between 35-40psi and the high side goes up to between 190-225 psi and the low side will not get cold.

Pressures are in spec, everything worked fine last year and now it all appears to be working and in spec but no cold air, no cold and sweaty low pressure side ???

WTF is it ?? I got two days of dicking with this and neither of us knows where to go with diagnosis ??

HELP......

 

[Chevy1925]

did you replace the reciever/dryer as well? if the lines were left open in humid weather for more than ten min it probably went bad. it doesnt have a huge affect on the a/c but its doesnt help the issue.

the high side seems low on pressure to me. generally i see atleast 275psi or more with the car at Rpms at 2k.

 

[GMC_2002_Dmax]

We saw it up at 300 psi and we thought it might be slightly overcharged so we pulled a little out, tried revving the car to 1500-2000 rpms, nothing.

I wouldn't think the receiver/dryer would be bad, maybe it is ??

 

[ecc_33]

If your going to do a new reciever dryer you will want to install a new orfice tube also. Its cheap small insurance. If trash went through the system they get plugged up quick. How long did the system hold vaccum for? Is the compressor short cycling? kicking on and off more than normal kinda fast? The low side seems alittle high and the high side is almost to low

 

[GMC_2002_Dmax]

No short cycling

 

[ecc_33]

Is the clutch staying on all the time. Sorry for the dumb questions in my head im trying to rule things out and my strong point isn't A/C as I don't work on that all the time. Have you tried driving it down the road( assuming you have as i know your mechanically inclined) usually a system with trash or a blockage the low side will be very low to a vaccum iirc. I really think it wasn't just the compressor clutch but the whole compressor itself is bad. Yea, after thinking about it i bet the compressor is wasted. Not sure on that car how easy it is to access but see if you can stethoscope it and see if any wierd noise is coming from the compressor itself. Please post what you find as i am curious

 

[GMC_2002_Dmax]

Clutch cycles fine, drove it down the road, no AC just hot air blowing.

 

[ecc_33]

i edited my post so read above at the end

 

[GMC_2002_Dmax]

Is the clutch staying on all the time. Sorry for the dumb questions in my head im trying to rule things out and my strong point isn't A/C as I don't work on that all the time. Have you tried driving it down the road( assuming you have as i know your mechanically inclined) usually a system with trash or a blockage the low side will be very low to a vaccum iirc. I really think it wasn't just the compressor clutch but the whole compressor itself is bad. Yea, after thinking about it i bet the compressor is wasted. Not sure on that car how easy it is to access but see if you can stethoscope it and see if any wierd noise is coming from the compressor itself. Please post what you find as i am curious

The compressor clutches are prone to shorting out on these VW's, the system had a full charge and wasn't open that long, in fact it held suction/vacuum all night until I swapped the O-Rings out today.

It held for an hour at almost 29"/Vac.

I might just buy a new R/D and Orifice as well as all new O-Rings and flush with Nitrogen.

This is why I usually buy a new truck every 4-5 years...........

 

[ecc_33]

I know what your saying but im thinking its the actual compressor itself. Not just the clutch. If it had a full charge before and no a/c it will usually be a bad clutch and or a bad compressor itself. Thats what it sounds like here, bad compressor. a system thats almost to high or high on the low side and almost to low or low on the high side is usually a bad A/C compressor. I hope that makes sense. As long as the system didn't get contamenated with stuff from the bad compressor you should be fine on the reciever dryer and orfice tube or expansion valve as some call it. As a rule of thumb a change O rings in the system that ive takin apart just for safe measures. If your holding that good of a vaccum i really doubt you have any leaks so thats good.

 

[Chevy1925]

If the compressor is bad there a some very good signs of it. One, the orfice tube will be packed with crap. Two, pressures will be relativly low. And three, it will be makin a lot of noise.

Id make sure your blend doors are going to the "cool"side. Make sure the electric fans are on with the a/c (normally one is dedicated to turn on when the a/c is on). And replace what you said you were gunna do. The orfice tube will tell your story on the compressor.

I would also charge the whole system with nitrogen to 150 psi after a vac test and spray every line/connection with soapy water. Sometimes a crack will seal under vaccum but not under pressure.

 

[Chevy1925]

I know what your saying but im thinking its the actual compressor itself. Not just the clutch. If it had a full charge before and no a/c it will usually be a bad clutch and or a bad compressor itself. Thats what it sounds like here, bad compressor. a system thats almost to high or high on the low side and almost to low or low on the high side is usually a bad A/C compressor. I hope that makes sense. As long as the system didn't get contamenated with stuff from the bad compressor you should be fine on the reciever dryer and orfice tube or expansion valve as some call it. As a rule of thumb a change O rings in the system that ive takin apart just for safe measures. If your holding that good of a vaccum i really doubt you have any leaks so thats good.

30-40 psi is pretty good pressure on the low side

 

[ecc_33]

Yea,I usually like to see it between 25-35 but your right its not bad. It helps to have someone around that does a lot more A/C work than i do lol. Good points!

 

[Chevy1925]

Yea,I usually like to see it between 25-35 but your right its not bad. It helps to have someone around that does a lot more A/C work than i do lol. Good points!

Lol i use to do alot of car a/c repair (living in az, you learn quick lol). Ive avtually seen a few cars where 50psi was concidered a good low pressure and 400+ was a good higb pressure

 

[GMC_2002_Dmax]

Compressor is quiet, clutch engages smoothly and stays on until the high limit switch is reached and then it kicks off as designed.

The system would freeze you out last year, would the compressor making proper pressures on the low side and high side rule out a bad compressor ?

Equal pressures on the low/hi when at rest should rule out the TXV or expansion valve?

The fact that the compressor is making the pressures but no cold means the expansion valve might be bad but then I would expect the low side to be up vs in spec.

 

[Chevy1925]

Does the air feel any little cooler than ambient? Even the slightest?

 

[GMC_2002_Dmax]

Nope

 

[Chevy1925]

I dont think your blend door is flipping over like it should. Even with the low, high pressure you should be feeling something.

If you really dont think its a blend door and it looks to be working correctly, put more freon in and bump the pressure on the high side to 300 and See where the low side is. If the pressure on the low side jumps to fifty or so, something is a miss in the low side.

Its sounds more and more like a blend door or expansion valve but with those pressures you should still feel something.

Do you have a thermometer you can stick in the vents?

 

[GMC_2002_Dmax]

I dont think your blend door is flipping over like it should. Even with the low, high pressure you should be feeling something.

If you really dont think its a blend door and it looks to be working correctly, put more freon in and bump the pressure on the high side to 300 and See where the low side is. If the pressure on the low side jumps to fifty or so, something is a miss in the low side.

Its sounds more and more like a blend door or expansion valve but with those pressures you should still feel something.

Do you have a thermometer you can stick in the vents?

Unfortunately it is not a blend door..........the cold side (low side) is not getting cold, it is not for whatever reason even at the pressures stated getting cold.......I have four other cars or trucks and tow others I have checked as well and within 20 seconds each of my other vehicles has a noticeable drop on the cold side, my son's 14 years old VR6 Passat wagon blows 42 degree air out of the vents, I can hang meat in each of my Dmax's.

Only reason I think it could not be an expansion valve (TXV) is because the pressures equalize when the compressor is off and the the low side drops and hi side rises when the compressor is running ??

Time to schedule an appointment with an AC guru and get it resolved.

if anyone has any more suggestions please keep them coming

:thumb:

I found this

http://www.aircondition.com/tech/questions/82/

 

[Chevy1925]

well if the expansion valve is stuck open, you can still see a pressure drop jsut by the difference in tube size and due to the condensor cooling the freon. Specially with the low high pressure you have going on. this is why i wanted you to add more freon. it would increase your low side pressure to "out of spec" if the valve is stuck open. Right now, your fighting yourself because atleast one thing needs to be taken care of before a difinitive diag can be made.

You do need a reciever/ dryer (if it was not capped when you opened the lines or if you blew air through it) and you do need more freon in the system. Pressure is more important in a A/C system than volume to a point since you are dealing with a very little volume of freon. kinda like a CP3 . If/when that is fixed and still absolutely no change in vent air temp you have a evaporator/expansion valve issue. we pretty much narrowed it down to that as a plug in the line would cause high, high pressure or freezing at the evaporator but with the freezing, you would still notice cold air at first then nothing. And if the expansion vlave is stuck open, there is nothing to restrict the freon to make it stay a liquid before entering the evaporator and turing back into a gas.

If i was a gambeling man, id be puttin a good chunck of my pay check on the expansion valve. this is jsut by going with what you and i have discussed.