2002 Pontiac Ram Air Trans Am ac is not cooling properly

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dannyual320
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Location: Montgomery, TX (just north of Houston)

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

Postby dannyual320 » Wed Sep 02, 2020 2:13 pm

A19, according to Rock Auto, my car's orifice tube color is black.
Al9
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Al9 » Wed Sep 02, 2020 2:50 pm

Good. If you're looking at a replacement, i'd recommend you use the fixed one instead of the variable one. The compressor's control valve likes the suction pressure to be as steady as possible while it's operating within the "destroke" suction pressure zone. Whenever a TXV is used with these compressors, it's carefully designed so that the metering pin never seats fully while the control valve is destroking the compressor in order to bring suction pressure up. No point in making a proportional control system turn into a bang-bang one.
dannyual320
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Location: Montgomery, TX (just north of Houston)

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

Postby dannyual320 » Wed Sep 02, 2020 4:18 pm

A19, thank you for your information. I'm planning on just replacing the OT with another black OT when I open up the system. I did notice on Rock Auto that they do offer "Premium" automatic adjusting orifice tubes but I'm going to stick with the OEM AC Delco part for less than 3 bucks.
dannyual320
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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

Postby dannyual320 » Wed Sep 02, 2020 4:40 pm

This non-working ac system is bothering me so I had to go outside and do yet another test. Those low H pressures that I got earlier today are not consistent with the higher H pressures I saw 3 days ago.

Ambient temp had increased to 90F. I restarted the car and the radiator fans running on low.

Idle-----------------1500rpm
H210----------------H210 rising to 240
L30------------------L25
vent 93F------------92F

I did a second idle and 1500rpm test and the pressures were a little lower on the L side and the vent was 90F



I then turned the ac OFF and then back on to MAX and now the H pressures went way up. More like what I saw 3 days ago.

Idle------------------1500rpm
H320----------------400
L24------------------24
vent 82F------------82F

Last test:

Idle------------------1500rpm
H350-----------------400
L25-------------------25
vent 77F-------------77F


Notice that the vent temps did inch down. The driver's door was open so the cabin of the car wasn't really getting cooler and the blower fan was on high for all tests that I've posted. There was plenty of water condensation dripping out of the bottom of the car. I did look closely at the water with my UV light and saw no dye.

These varying High pressures have me baffled. There is no obstruction in front of the condenser and the two fans are running on high speed when the High pressures are up higher.
Al9
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Al9 » Thu Sep 03, 2020 1:43 am

The "automatic adjusting" stuff is nothing but an orifice tube that pretends to act as a cross-charged TXV, basically by restricting as the high side goes down due to limited compressor capacity and the opposite (the comparison comes from the fact that the cross charged TXV would be acting with positive superheat and hence flow restriction in this case, unless heat load was very low so to easily pull suction pressure below the "cross" value even at idle; and then eventually lose that restriction as the suction starts falling due to a sudden increase in compressor capacity). Only really useful with some fixed displacement compressor systems, as proven here in this thread. Keep in mind that if the evaporator gets starved of refrigerant while the compressor is running destroked, you will hear an awful moaning/motorboat like noise inside the car (here's one example https://www.youtube.com/watch?v=AHB-LkzL7ng&t=2s). So just use the standard one.

The evaporator/low side getting cooler/down as the high side climbs up is a peculiarity of mechanical control valves. The pin inside the top orifice (the one responsible for getting the compressor destroked) gets pushed down as discharge pressure increases, actually preventing the bellows from expanding and pushing the same pin upwards to the open orifice position until a lower suction pressure is met. That is, the destroke pressure depresses (i.e. the evaporator is able to get colder) as the discharge pressure increases. In my CVC compressor (and same control valve as yours) equipped car this is made evident by the vent temperature beginning to feel a little colder a short while after coming to a halt, provided the correct charge is inside. Look up patent US4428718A to understand this better.

Lots of water dripping from the condensation drain and no reheating issue still tells me that aside from a possible overcharge/residual air amount in system (do what i and Tim said to rule all of this out) the evaporator may be getting cold but warm air is somehow running around it rather than through it. The repeated evaporator freeze-up condition you stated possibly ended up causing some damage. Maybe too many bent fins/damaged packing?
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bohica2xo
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby bohica2xo » Thu Sep 03, 2020 4:25 pm

18 year old electric fans. You are chasing your tail.

Spray the condenser with water and watch the pressures. You should be able to get the system to stabilize at the control valve pressure on the low side - if you can get rid of the heat.

We went through this at length on the old board. The electric fan may be running at "high" as far as the pcm is concerned, but the tired fan motor can't cope with the heat load.

Clean the heat exchanger stack too. While the face of the condenser may look clean, it can have plenty of bugs & debris deep in the fins. Avoid high pressure washers, just use a good surfactant like Simple Green sprayed in to the fins of a cold condenser. Let is soak for a few minutes, and flush it out with a garden hose. You may be surprised at what comes out.
dannyual320
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby dannyual320 » Fri Sep 04, 2020 8:40 pm

bohica, thank you for your information as well. When my electric fans were running on high, I was able to get my hand behind the passenger side fan and confirm that it was pulling a lot of air. I wasn't able to get my hand in a good position to confirm that the driver's side fan was pulling the same amount of air.

Over the course of the next week, I'm going to disassemble the whole "cold air intake" system sitting right above the radiator so that I can get to the top of the radiator and condenser. I'm going to visually confirm that there is no debris between the two. I'll clean it all up just to be sure. While I've got things apart, I'll try to figure out whether or not those two electric fans are working at 100%.

On Wednesday, I sprayed down the condenser with water and the H side pressure dropped a lot. I posted those numbers in post #10 (2 Sep 20 @4:12pm.)
dannyual320
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Joined: Tue Aug 18, 2020 2:23 pm
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby dannyual320 » Fri Sep 04, 2020 8:46 pm

Earlier in this thread I had mentioned a Robinair RG3 recovery machine. In addition to the Trans Am that I'm currently working on, I have two project cars in the garage that will need ac work. My wife suggests that I just buy the recovery equipment and be able to do what I need to do when I need to do it. Unless you guys tell me not to buy my own equipment, I think that I'm going to add this machine to my tool collection :D .

I have a question on recovery whether I do it myself or if I paid the shop $100 to do it. Doesn't some oil come out of the ac system along with the refrigerant? If so, wouldn't that affect my scale's weight reading? How would I know how much oil to add back into the system?
Al9
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Re: 2002 Pontiac Ram Air Trans Am ac is not cooling properly

Postby Al9 » Sat Sep 05, 2020 3:17 am

Yes, some oil always comes out with the recovered refrigerant, but the recovery machine has an oil separator and a measuring scale/bottle. If the technician isn't a complete idiot, the same amount recovered will be injected back into the system right after the vacuum is done as fresh oil.

By the way it's a very small amount, around half an oz/1 oz depending upon the system's size, to the point that most shops only store and use Ester 100 and PAG 100 as universal oils, since the viscosity/type apparently won't matter in that case as long as it's compatible with the refrigerant (things may start to get wrong once they fill a replacement compressor with the same universal oil, not caring about the proper viscosity required; i saw the shop that replaced my compressor fill a Denso swashplate unit with PAG 100 when it should have been PAG 46, and luckily enough i supplied them with the right oil for mine). If you want the shop to use the proper oil for your compressor, supply them with a bottle of PAG 150/PAG Blue.

A RRR station once pulled out half an oz of oil from my little Kei car featuring front AC only and a little more than a pound of nominal refrigerant charge.
dannyual320
Posts: 37
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

Postby dannyual320 » Sat Sep 05, 2020 7:16 am

So it sounds like only 1/2-1 oz of oil would come out of my Trans Am's ac system during a refrigerant recovery. According to Rock Auto, my car should have PAG150 type oil.

Unfortunately, the little Robinair RG3 doesn't come with an oil separator so I would have to just guess on how much PAG150 to add back in.

Here is the Robinair RG3 that I was thinking about buying:

https://www.robinair.com/products/rg3-portable-refrigerant-recovery-machine

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