Engine Size: 3.5L
Refrigerant Type: R134a
Ambient Temp: 70
Pressure Low: 0
Pressure High: 0
Country of Origin: United States
Hi all. I'm new here, and fairly new to automotive a/c, so I thought I'd stop by with a couple questions. My car has a V7 variable displacement compressor that's showing the symptoms of a stuck refrigerant control valve - low pressure side reads too high, only cools at high RPMs - so I'm going to throw a new one in there, which sounds cheap and easy. I have a friend with access to a shop that's going to evac the system for me, as I understand I'm supposed to do that with the valve change.
My questions: I don't know if quickly pulling a valve out and popping a new one in is enough to count as opening the system and all the extra work that comes with it. Do I need to replace the receiver? I'm asking because I don't have any PAG on hand and hate to buy an 8oz bottle when I only need 1oz. Do I need to change the orifice tube? I'd rather not if I don't have to - I've heard the brake master cylinder needs to come off to get to it. Do I need to worry about a long deep vac before charging or would 15 minutes on a crappy Harbor Freight venturi-style (I bought one long ago for another car and then it got wrecked and still have it out sitting in the box in the garage) down to 28" be good enough if I'm not introducing moisture to the system?
you need to pull a long deep vacuum with a good pump. The Harbor Freight venturi type is a poor pump. As long as the system is opened, change the accumulator/drier and at least inspect the orice tube, They are inexpensive so I would replace it. Add the oil as you will only want to do this job once.
I don't inspect or open the orifice tube -especially on W cars- that brake booster is a PITA- unless I see a need to - such a a restriction on the high side- swap the control valve- no need to change accumulator- I've ran tests without using a desiccant bag in A/Ds and 134a- not a problem.....just everyone is used to changing them to pay for the warranty on the compressor- as long as oil is not contaminated- you will be fine. It is quite possible to change control valve without removing compressor from engine.
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
If I opened a 12 year old vehicle's AC system, it is going to get an accumulator. Just covering my butt. 15 minutes open to the atmosphere and the oil starts to pick up moisture. If you are not replacing it, at least give it an over night evacuation with a good pump.
Well it seems to be a moot point, now. I got under there today, and the RCV is pointing straight down at the frame of the car that is about 1" away from it. No way to get it out like that... considering if I take of the belt and unbolt the compressor if I can tilt it slightly without removing the lines. It looks like the a/c lines are rubber hoses most of the way up to it, so they should give it plenty of room to move. If that doesn't work, I'm going to have to take the compressor off to change it and then I'll just replace the accumulator and pull a good vac.
Edited: Wed June 25, 2014 at 12:03 PM by Nabby
Man, don't ever work on these shortstar engines. I had to remove the battery (and the plate that holds it), airbox, coolant hoses, fan assembly, top front motor mount, thermostat housing, overflow bottle, alternator, idler pulley, and under-engine deflector just to get the compressor out. I didn't bother with the orifice tube, but I did replace the receiver while I had the airbox off (it's under that). It was an 8-hour job from start to finish, including vac, recharge and refilling/air-bleeding the coolant system. But I have cold air again.
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