2002 Pontiac Ram Air Trans Am ac is not cooling properly

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Al9
Posts: 257
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Joined: Tue Mar 10, 2020 3:26 am
Location: Southern Europe

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

Post by Al9 »

Whenever you're in doubt, a visit to an RRR station equipped pro is always money well spent, no matter how much.
When you turned the compressor on, it pulled refrigerant inside so slowly because, with so little refrigerant inside and so cold ambient temperature, it was fully destroked.

If it can be of consolation somewhat, i'm getting a steady (compressor is correctly regulating stroke at all rpms) 49F vent at 72F ambient with my new compressor and the new radiator fan, a new and externally clean condenser, a genuine (albeit second hand) factory TXV and the correct rating compressor control valve for my car. Not a heater core/box issue since it does the same with a cold engine. Charged in the summer with an RRR station, flushed system, every required oz of refrigerant and DEC PAG oil inside right before engaging the clutch for the first time. Double checked that everything was leak free because i got the control valve replaced to the correct one about 2 weeks later after having the compressor fitted so it again got serviced with an RRR station and the charge weight got evaluated. Either normal, or someone provided me with a valve whose rating is higher than what the color states. Vent temperature definitely felt colder (unless in very hot sunny days, when AC started acting up) right before i replaced the radiator fan (one cause for the AC issues i had), and right after replacing it, unfortunately, ambient never managed to climb up above 72F where i live, so i'll have to wait for next Spring.

In other words, wait for warmer weather to evaluate your system performance further. As i said earlier, the control valves used in both our compressors (yours and mine) have that little quirk of dropping vent temp as the high side pressure climbs up, and the opposite.
dannyual320
Posts: 49
Joined: Tue Aug 18, 2020 2:23 pm
Location: Montgomery, TX (just north of Houston)

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

Post by dannyual320 »

Thank you Al9 for your consoling words describing what is going on.

I was wondering if that variable displacement compressor was "destroking" since I never saw a high side pressure above 70 last night.

About a week ago, I told my father-in-law that . in the past, I've noticed that auto ac systems act differently in the cool weather vs the heat of the summer. I told him that I was a little apprehensive about doing this final reassembly, charging and testing while we're experiencing abnormally cold temperatures for the Houston area. On the other hand, I just wanted to get it done.

For now, I'm just going to give it a rest and like you, wait for warmer weather to do a proper test.
dannyual320
Posts: 49
Joined: Tue Aug 18, 2020 2:23 pm
Location: Montgomery, TX (just north of Houston)

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

Post by dannyual320 »

Hello everybody. We've had a cool winter/early spring here in the north Houston area. Remember the great Texas freeze in February?

I drove the Trans Am for a quick drive to the gym and back on Saturday, 27 March 21 and it was in the upper 70s and muggy so I said that this would be a decent time to try the ac system. It had been a long time since I'd turned the ac system on. It's a short drive back from the gym (4 1/2 miles) but I did see 45F on my thermometer with the ac on MAX. I'd rather have seen 40F but I was satisfied with the 45F.

Back in December 2020 when I was charging the system in the cold ambient conditions, I was just a little shy of 24 oz of refrigerant because I just couldn't get it in. As the weather warms up over the next month or two, I'll continue to monitor my ac's performance and if need be, I'll add another ounce or or so to bring me up to 24oz total.
Al9
Posts: 257
Joined: Tue Mar 10, 2020 3:26 am
Location: Southern Europe

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

Post by Al9 »

See? Vent temp climbed down as heat load (humidity is also additional heat load) increased.

I'd have turned AC on for a few mins during any warm spell.

Rather than adding one ounce or so, i'd recommend you visit an RRR equipped pro and have everything recovered, weighed and restored to proper spec. Dead on charge weight is critical with this system, since, as you've just seen, it uses discharge pressure to adjust vent temperature.

Other posters with V5/V7 comp equipped vehicles said, in archived posts that now got removed for some reason, that the real icy blast will come around 100F ambient.
dannyual320
Posts: 49
Joined: Tue Aug 18, 2020 2:23 pm
Location: Montgomery, TX (just north of Houston)

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

Post by dannyual320 »

Al9 wrote: Tue Mar 30, 2021 1:12 am See? Vent temp climbed down as heat load (humidity is also additional heat load) increased.

I'd have turned AC on for a few mins during any warm spell. If I'm being 100% honest, I'll have to admit that there was a fear factor that kept me from doing this. I was afraid that the ac system wouldn't work or that the refrigerant had leaked out since December

Rather than adding one ounce or so, i'd recommend you visit an RRR equipped pro and have everything recovered, weighed and restored to proper spec. Dead on charge weight is critical with this system, since, as you've just seen, it uses discharge pressure to adjust vent temperature. This has been a long thread that has spanned months and many posts. I do own a Mastercool refrigerant recovery system as well as a very good air conditioning service scale.
That being said, I'm confident in my 1.43 lbs of refrigerant added in December. The only unknown would be if any of my seals weren't holding and the system is leaking some.


Other posters with V5/V7 comp equipped vehicles said, in archived posts that now got removed for some reason, that the real icy blast will come around 100F ambient. This I understand but I think that it goes against "logical thinking." I would guess that most people would assume that an ac system would produce colder vent temperatures if the ambient temperature were cooler. I'm confident that my vent temperatures will be even better than 45 when the hotter summer temperatures arrive here before the end of May.
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