2002 Pontiac Ram Air Trans Am ac is not cooling properly

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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Tim » Tue Sep 15, 2020 11:48 am

So when you put the replacement compressor on? How much oil did you add?
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby dannyual320 » Tue Sep 15, 2020 5:44 pm

Tim wrote:So when you put the replacement compressor on? How much oil did you add?


Tim, the compressor and all the other ac parts are factory OEM. Other than add a little refrigerant earlier this summer, nothing on the ac system has ever been touched. I'm the original owner of the car.

I did have trouble with the compressor starting about 8-10 yrs ago in that the evaporator would freeze up on drives longer than an hour. I guess the variable displacement compressor wasn't "variable displacing." I was told on this forum that the only fix was to replace the compressor. Since the ac system back then worked fine otherwise, I decided to live with it since 99% of my drives in this Trans Am are way under an hour.

A19 mentioned a compressor control valve several posts ago. Does that control the variable displacement?
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Al9 » Wed Sep 16, 2020 1:09 am

Yep, that's what controls compressor displacement. I even told the patent number where its inner workings are described to great depths.
IMHO, definitely worth to try replacing it before condemning a compressor. Had yours been a Sanden SD7V16 comp, things would have been completely different. In the Sanden's case, i would have told you to go get a new compressor too.

But the Harrison V7? Go Google for V7 compressor pictures. See that colored dot on the head, that is, to the compressor's back (generally pointing downwards with the compressor mounted on the car), surrounded by a little circlip? That's the control valve. It's an externally accessible control valve. Recover the refrigerant, pull circlip out, pull valve out, put new one back in, put (preferably new) circlip back in, done. Knowing which color yours is, however, is important. The color tells you how cold your evaporator will get before the compressor will destroke with that valve in place. Different colors because suction line length can vary (longer suction line=a greater pressure drop will develop between the evaporator and the control valve at maximum compressor stroke) and evaporator wall thickness can vary too. Price of a new control valve? Around 10-20 bucks. Waaay less than a new comp. Comes with new o-rings and a new filter element too.

PS Nick's Al9 (as in ay-ell-nine) ;)
Last edited by Al9 on Wed Sep 16, 2020 8:53 am, edited 1 time in total.
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby dannyual320 » Wed Sep 16, 2020 7:27 am

Oh. A "L" 9! I apologize for getting this wrong. My eyes just aren't as good for near vision as they used to be! On the other hand, my distant vision has been improving as I've been getting older :D !

AL9, you've got me sold on trying a new compressor control valve. I just looked up these control valves and I see that one online company sells two different color control valves for my car's compressor:

1. Purple (41psi)
2. Orange (45psi)

Is this the right one from Tim's online store?

https://www.ackits.com/31-55313-control-valve-purple-gm-v5-r134a-11517?keyword=control%20val
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Al9 » Wed Sep 16, 2020 7:49 am

No problem about the nick.

Orange sounds way too high to me.
If your compressor comes with the purple 41 psi control valve, both the purple 41 psi one and the blue 42 psi one might be fine as replacements. Your choice.
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Tim » Wed Sep 16, 2020 7:54 am

Santech list Purple for the 02 5.7L

I can understand if you are just trying to make it better. But if the compressor was never changed. Why mess with what came from the factory? Just asking is all.
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby dannyual320 » Thu Sep 17, 2020 8:22 am

I can understand if you are just trying to make it better. But if the compressor was never changed. Why mess with what came from the factory? Just asking is all.


Tim, are you saying that I should change out the original control valve with a new purple valve? Do you think that the control valve could be the problem with my ac system?
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Tim » Thu Sep 17, 2020 8:28 am

No. Just saying what vendors list as the OEM CV.

I had a 96 Z28 for a short time. It never cooled well. Not sure about how similar they are. You might be doing the best the system, will do. Way too many pages of posts to read them all. What I have read is your pressures did not seem that far off.
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Al9 » Thu Sep 17, 2020 8:51 am

He probably meant to comment my suggestion of a 1 psi higher rated valve. I suggested it only because you stated (in the opening post) that you had evaporator freeze-up issues, as if the compressor wasn't destroking once the correct evaporator pressure was met or wasn't destroking at all.
1 psi higher rating isn't going to impact cooling performance or noise, especially on an orifice tube system, and it may prevent further occurrence of the freeze-up issue, provided that it's just a bad design issue (can happen). If the problem turns out to be elsewhere than the compressor, it's still routine maintenance as i'll explain better. If the problem turns out to be the compressor itself, you can remove it and keep it as a spare for a replacement compressor.

I'm not trying to sell anyone into buying a new control valve or anything like that. I recently had a 17 year old one removed from my car's (now decommissioned) CVC compressor unit, and noticed the 3 inner o-rings were terribly shrunken compared to original spec.

Shrinking of the 3 inner ones means refrigerant being routed elsewhere than supposed to, and this means abnormal compressor displacement regulation. A shrunken outer one, on the other hand, means a refrigerant leak.

That's why i consider a new control valve as a routine maintenance item for any compressor having them (except those with internally mounted ones, where opening the compressor's head up can equate to opening a can of worms).
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby dannyual320 » Thu Sep 17, 2020 11:36 am

Tim wrote:No. Just saying what vendors list as the OEM CV.

I had a 96 Z28 for a short time. It never cooled well. Not sure about how similar they are. You might be doing the best the system, will do. Way too many pages of posts to read them all. What I have read is your pressures did not seem that far off.


Tim, yes this is a long thread and I should probably summarize it soon. Other than the evaporator freezing on drives longer than 1 hour, my black Trans Am's ac always cooled very well in the Florida and Texas heat. At the beginning of last summer, during my first couple of ac uses, it seemed to take just a little longer for cold air to come out of the vents. After several uses, the ac seemed to be working normally and I just thought that maybe it needed a "wake up" from not using it during the cooler winter months.

At the beginning of this summer, the "wake up" was much worse. No cool air for quite a while and even then, it didn't get very cold. I started driving with a thermometer in the vent and could only get 55F temps at best. It would take a while to get down to 55F. I never measured the good working OEM vent temperatures but I would guess they were close to 40 degrees.

Even before I recovered the refrigerant several days ago, I couldn't get any cold air. Vent temps were barely lower than ambient. After running the ac for about 10 mins (doors open, fan on high) I got the vent temp down to the mid 70s. Not good.

I've been driving my wife's 2013 Honda CRV and the ac puts out cold air almost immediately after start up. I've also been driving my big, 2001 Ford F250SD crew cab diesel and it too puts out cold air almost immediately. With both of those perfectly working ac systems, I usually end up turning the blower speed down after a short while even when it's 95+F outside.

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