• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

Rear AC repair info: Yes, it has a Thermal Expansion Valve (TXV)

Great info FERM, I'll factor thickness to see if there is much difference if not I'll use that condenser you suggested as it is a direct fit. Again thanks!
 
Ok, I worked out the depth on each condenser the one I have now is 418.5 square inches, the one FERM suggests is 447 cubic inches or about 6.40% larger than the one I have and the BIG condenser is 467 square inches or about 10.80% larger than the one I have now and about 4.4% larger than the condenser FERM recommends.
 
My condenser is 16" x 35" or 560 sq " Its the newer block type, I had the proper fittings welded in like the old condenser had. I had to make a couple custom hoses to. The orifice tube go's right into the evap.
 
Burning oil said:
My condenser is 16" x 35" or 560 sq " Its the newer block type, I had the proper fittings welded in like the old condenser had. I had to make a couple custom hoses to. The orifice tube go's right into the evap.
Click to expand...

Have a part number for it, is it 1" thick core, or?

I had to subtract (155.45 sq inches) of total frontal square inches because of the big units core thickness of .75". BTU rejection is a big factor as FERM pointed out but by .25" less depth 155.45 is a lot of square inches lost on the big core I found.
 
Burning oil said:
http://www.jcwhitney.com/p3088421/sku-8739585.jcwx

Cant remember where I bought mine, this was at the top of google search.
It fits my truck real nice and I'll be able to use stock mounts.
Click to expand...
Did the math; about 566 square inches frontal however it's .63" thick so minus .37" of 566 sq in = 209.42 square inches so that unit has 356.58 actual square inches of cooling surface.

The actual cooling surface is what FERM was talking about determines the efficiency of the condenser BTU rejection and as you can see 566 square inches is not that size when you factor the thickness or depth of the core in this case, if the core was 1" thick then it would be 566 square inches actual cooling surface, if 2" thick then it would be 1,132 square inches actual cooling area.
 
Last edited:
Take a look at the oil coolers (with an IR temp gun) in front of the condenser. If the transmission oil cooler is getting hot oil from the transmission first before the oil goes through the radiator it will heat up the freon just before it leaves the condenser. The Engine Oil Cooler doesn't help. Keep in mind the AC condenser runs at 160 degrees (suggest this is near the max temp it gets up to.) So oil that is hotter than the condenser in front of the condenser is not cooling or heating the condenser up.

I got good results making sure the trans oil cooler got oil already cooled by the radiator and leaving the EOC in place. I would get better results if I moved both oil cooler behind the condenser. There is a "V" support in the way between the radiator and condenser.
 
My trans fluid flows from converter to the radiator then to dual fin plate coolers and gets to 150 deg f in the pan on triple digit days tops, the oil cooler runs hotter and I'm trying to figure just where to place them after my CAC/IC install because the new condenser will fill the space the coolers use now. In any case I'm trying to place the aux coolers below the batteries behind the radiator support and cutting properly sized opening in it to connect ducts to ram cool them at speed and fans during idle, slow moving and stop and go traffic.
 
Perhaps this is moderately related and maybe not. Years ago - maybe close to 15 years - I got some advice from a guy on a Chevy 4x4 forum that said to always run the rear fan on medium or higher when the rear A/C was on. I can't recall the problem he said it would create if we did not, but we've always done this since we've had our '94 and we've never had an issue with the rear system. We always control all HVAC from the driver seat. Always.

Related?
 
SnowDrift said:
Perhaps this is moderately related and maybe not. Years ago - maybe close to 15 years - I got some advice from a guy on a Chevy 4x4 forum that said to always run the rear fan on medium or higher when the rear A/C was on. I can't recall the problem he said it would create if we did not, but we've always done this since we've had our '94 and we've never had an issue with the rear system. We always control all HVAC from the driver seat. Always.

Related?
Click to expand...
I seem to remember rear HVAC on medium or high prevented evaporator from freezing.
 
FellowTraveler said:
I seem to remember rear HVAC on medium or high prevented evaporator from freezing.
Click to expand...
SnowDrift said:
Perhaps this is moderately related and maybe not. Years ago - maybe close to 15 years - I got some advice from a guy on a Chevy 4x4 forum that said to always run the rear fan on medium or higher when the rear A/C was on. I can't recall the problem he said it would create if we did not, but we've always done this since we've had our '94 and we've never had an issue with the rear system. We always control all HVAC from the driver seat. Always.

Related?
Click to expand...

Whenever the A/C is on, the rear fan NEEDS to be on to prevent liquid slugging of the compressor, and starving it of oil. The problem was with the rear TXV used up till 95 would completely close off when the rear fan was off. This would allow liquid refrigerant to collect in the high pressure line to the rear A/C, and with it oil would collect. After long enough, the high side line to the rear could collect enough oil in it to starve the compressor of oil, and cause compressor failure. Starting in 96 GM used a different TXV for the rear A/C that would never completely close off to help reduce the amount of oil that could collect in the rear line. Also by not running the rear fan, the rear system will get cold enough to pull enough charge out of the system to make the compressor rapid cycle like it would when it is low on charge making the front air get warm. I pretty much always run my rear fan on low, and my front one on 2. I can hang meat inside the cab on a 95 degree day once it stabilizes the temp inside. I RARELY turn my front fan above 2, or put the rear on medium, just don't need to.
 
I was going to make a joke about hanging meat in my truck to, but I'll just zip it (oh wait that could be another joke:) )
 
THEFERMANATOR said:
Whenever the A/C is on, the rear fan NEEDS to be on to prevent liquid slugging of the compressor, and starving it of oil. The problem was with the rear TXV used up till 95 would completely close off when the rear fan was off. This would allow liquid refrigerant to collect in the high pressure line to the rear A/C, and with it oil would collect. After long enough, the high side line to the rear could collect enough oil in it to starve the compressor of oil, and cause compressor failure. Starting in 96 GM used a different TXV for the rear A/C that would never completely close off to help reduce the amount of oil that could collect in the rear line. Also by not running the rear fan, the rear system will get cold enough to pull enough charge out of the system to make the compressor rapid cycle like it would when it is low on charge making the front air get warm. I pretty much always run my rear fan on low, and my front one on 2. I can hang meat inside the cab on a 95 degree day once it stabilizes the temp inside. I RARELY turn my front fan above 2, or put the rear on medium, just don't need to.
Click to expand...

Thanks FERM for the good info.
 
FellowTraveler said:
I seem to remember rear HVAC on medium or high prevented evaporator from freezing.
Click to expand...

This condition is also described in post #1 as the sensor for the TXV being loose from the evaporator pipe. However, I agree with FERM's answer. Adding to it the lack of a accumulator for the rear is why a liquid slugging condition can exist. The real solution to slugging would have been to join the suction lines Before the accumulator or feed both evaporator lines into a single accumulator.
 
WarWagon said:
This condition is also described in post #1 as the sensor for the TXV being loose from the evaporator pipe. However, I agree with FERM's answer. Adding to it the lack of a accumulator for the rear is why a liquid slugging condition can exist. The real solution to slugging would have been to join the suction lines Before the accumulator or feed both evaporator lines into a single accumulator.
Click to expand...
GM didn't put an accumualtor in the rear line because all of that 5/8" ID tubing from the rear to the front acts as an accumulator, so it isn't needed. All an accumulator is is a storage vessel for liquid refrigerant as to prevent liquid from making it to the compressor when the system pulls down and doesn't get enough heat in it to boil off all the liquid before it exits the evaporator.
 
You must log in or register to reply here.
Back
Top