A/C on my Daytona not working properly

[DoubleD]

I have a 1992 Daytona IROC R/T. Long ago the stock a/c condenser was removed. I have recently replaced that condenser with a brand new unit out of a 1992 Dodge Caravan. This is a smaller thicker unit, I have a large front mount and the normal TII radiator so the stock condenser would not work. I had the A/C professionally charged, the first night I got it, it was working great it was a nice 73 degree evening and I drove the car for a least an hour with the A/C on the whole time. The next couple of days I drove the car to work, the A/C would be cold right away, then it would blow hot for about 2-3 minutes and then blow cold for about a minute, it cycled like this all the way home on a 85 degree day. I have rebuilt the compressor, I replaced the condenser, drier, expansion valve, and all seals. I cleaned the evaporator when I had it out of the car this spring.

My theory is the system is overcharged now with the different condenser that's smaller, but I am unsure. My A/C guy is not a specialist and can charge and evacuate with a nice system, but does not have a lot of knowledge on the A/C system. I know the refrigerant is not leaking out. It is charged with R134a
Just last night I was driving the car and i Had nice cold A/C for about 2 mins after turning it on and then it went warm after that. Any help is appreciated! Thanks

[4 l-bodies]

Bradd,
Did you install an expansion valve for r132a or r-12? My guess would be cycling or low pressure switch is bad if it is not low on refrigerant. When it goes warm is the compressor clutch engaged or disengaged? My guess is the compressor disengages. What are the pressures on the discharge and suction side when compressor is running? It would be good to note temps of ambient air and AC outlet vent temps as well while you get pressure readings. Probably need to dignose this with gauges attached.
Todd

[A.J.]

When I build an AC system with either aftermarket universal parts or parts from different vehicles, I have to come up with a NEW charge for the system. I do it on the hottest day possible and then charge the system starting at one pound and adding two ounces at a time while watching the temp coming out of the dash and the high and low side pressures on the gauges. Sometimes I over charge it and have to suck it back out and start over until I get it right.

[DoubleD]

Bradd,
Did you install an expansion valve for r132a or r-12? My guess would be cycling or low pressure switch is bad if it is not low on refrigerant. When it goes warm is the compressor clutch engaged or disengaged? My guess is the compressor disengages. What are the pressures on the discharge and suction side when compressor is running? It would be good to note temps of ambient air and AC outlet vent temps as well while you get pressure readings. Probably need to dignose this with gauges attached.
Todd

Todd,
I just cross referenced all of the parts that I replaced, the expansion valve and drier is compatible with R12 and R134a. I talked to the local shop that charged it before, they are going to use A.J.'s method to evacuate and then re-charge the system. When it is cooler out at night, the A/C is operating correctly. I have a low pressure gauge and I have checked it a few times over the week, with a cold engine, the system pressure has held steady at 70 psi all week. Car's headed back to the shop on Monday, I hope to have a positive update then.

[Force Fed Mopar]

I've always found most vehicles to work best with around 40psi on the low side.

[A.J.]

I've always found most vehicles to work best with around 40psi on the low side.

Correct 30-40 psi on the low side. 70 psi is WAY to high for the low side. I bet the high side switch is shutting the system down because it's over charged. R134a runs about 25% less charge than R12.

[DoubleD]

70 psi was with a cold motor, not running and sitting over night on the low side, in the time I assume the pressure in the system stabilized. I did this just to make sure the system was holding pressure. I did some calculations and the overall condenser core in my car is 39% smaller than the factory one (92 caravan).

[A.J.]

PSI readings without the system engaged are worthless other than to tell if there is anything in the system or not. Even if you have a leak, unless it's LARGE, psi readings with the AC off won't tell you anything.

Condenser size doesn't matter as much as the type. I replace the factory condenser in my wagon with a smaller more efficient one and it blows colder than the larger factory one.

[mopar-tech]

PSI readings without the system engaged are worthless other than to tell if there is anything in the system or not. Even if you have a leak, unless it's LARGE, psi readings with the AC off won't tell you anything.

As a trained Mopar a/c tech I politely disagree. Gauge readings while running give you much useful information as long as you know what to look for.

[A.J.]

As a trained Mopar a/c tech I politely disagree. Gauge readings while running give you much useful information as long as you know what to look for.

We're saying the same thing, the system has to be turned on with the engine running to make a gauge reading.

[DoubleD]

Ok guys, I picked the car back up from the shop last night, this things is just being a nightmare. Going from the tech that charged it, they put 16 oz in the system, the AC was blowing cold but the compressor was getting really hot. What could cause this?
I have the car back now, it was fully evacuated when I went to pick it up, the system is currently under vacuum. What temperature should the compressor get up to while running? I am debating just tossing a pound in the system and then see how it works, I have a temp gun so I can get the accurate temp of the compressor. This is just becoming quite the pain to get AC in the car and to really figure out what is wrong.
Also, how warm should the metal line be leaving the compressor for the condenser?
Thanks for everyone's help figuring this stupid system out.

[83scamp]

They get hot, you won't be able to keep your hand on it. Not sure how much different the A/C system is on your 92, but my 89 took 36oz of R134a to get the system fully charged, and the gauges reading what they should...

[DoubleD]

The stock system held 32oz or 2 lbs. I have a different condenser that is 39% smaller than the factory one, so I calculated that out to be 19.5oz capacity. I am not sure how accurate this is. The gauges reading from the shop were good at right around 40psi low side.
The tech at the shop said they usually don't get as hot as mine was getting, so I am going by that, I prefer an actual temperature number instead of a generic term thou.

[DoubleD]

Decided to put 12oz in the car last night. After adding the can, the gauge was jumping all over and was averaging 50 psi on the low side, thinking I have a blockage or my compressor is not working properly.

[83scamp]

Could be the dryer. That's the conclusion I came to on mine. I had good pressure, but no cooling. When I bled the system, I watched the gauges until it showed virtually nothing. Went to unhook the lines, and I still had pressure behind the dryer, a lot of pressure( shot oil about 3 ft in the air). Let it bleed off a while longer, and still had pressure , but low enough I could unhook stuff.

I replaced everything but the condenser & evaporator. System works pretty good now. Not as cold as newer systems, but enough to keep me comfortable...

[A.J.]

Decided to put 12oz in the car last night. After adding the can, the gauge was jumping all over and was averaging 50 psi on the low side, thinking I have a blockage or my compressor is not working properly.

A fluttering needle usually indicates bad valves in the compressor, just like an engine with a fluttering vacuum needle.

[DoubleD]

When I am driving the car the A/C will blow cold for awhile 5-10 mins while driving, when the car is sitting in traffic no cold air. As I am driving at some point the check engine light will come on for a second and then the A/C will stop blowing cold. I am thinking there is something wrong with my compressor. Should the car bog down and be noticeably slower with the A/C on, I mean like almost boggy, it night and day with the AC on and off?

[acannell]

When I am driving the car the A/C will blow cold for awhile 5-10 mins while driving, when the car is sitting in traffic no cold air. As I am driving at some point the check engine light will come on for a second and then the A/C will stop blowing cold. I am thinking there is something wrong with my compressor. Should the car bog down and be noticeably slower with the A/C on, I mean like almost boggy, it night and day with the AC on and off?

Does the car run fantastic normally? The A/C will put big transient load on things and is depending on the idle control system to raise the idle. If the idle-raising system isnt working for some reason, and the car doesnt idle well normally anyway, I could see the two combining to cause a near stall

[DoubleD]

The car does run fantastically in every other situation. Idle is not an issue normally. I found a good deal on a re manufactured unit with a warranty so I'm going to install that and see what happens. I rented the manifold gauges and electric vacuum pump from autozone. I'm going to try to do it all myself correctly and find any issues out on my own.

[black86glhs]

I wonder if the expansion valve is not working and causing a high low side pressure. This will cause high compressor temps and the AC will eventually get warm as the flow in the system drops.