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Date: Wed, 25 Jun 1997 23:33:47 -0400

I would estimate that Jim's truck was blowing out air as cold as a normal car with good a/c, about 40 degrees. I think Jim F. was having Lynch install this upgrade on his truck along with the other maintenance.

What year and type truck do you have? According to my 95 shop manual you should get a 30 to 40 degree temp drop from outside ambient measured at the air intake or there is probably something wrong. The biggest problems are hot water valve not closing causing hot coolant to flow into the heater, compressor not kicking in or a leaky discharged system.


What is the vent temperature now? An a/c unit that yeilds 55 to 65 degree air on a 92 degree day sounds dreamy to me, so I can't imagine what a "good" a/c is capable of doing!

Date: Thu, 26 Jun 1997 09:22:37 -0400

Not true. A/C systems in cars even have valve to sense when the evaporator freezes up. One of the reasons you need antifreeze in your car in the summer is because of the potential of the heater core freezing and spliting from the A/C. I looked in my Mitsubishi Diamonte shop manual and they say the discharge air temp should be 32 to 37 degrees. I have a Porsche 928 that I think is overcharged and actually froze up last weekend when it was 92. I had to shut the A/C off for a few minutes before air started to blow out. Automotive A/C systems are supposed to be this cold. If your Cherokee is as warm as you say it has problems.

Actually the Hummer's A/C is uniquely inadequate in all but 1997 trucks. What I was saying is that if you install their fix which consists of a new condenser and an electric cooling fan the truck will work the way it should have all along.

You can't compare a car with a house or a fridge. If you measure the discharge air temp at the evaporator in the duct ( central forced air ) it will be much colder. By the time you measure the temp at the discharge duct it will have risen because is has been diluted with warm air and duct losses. If your home unit A/C temps are as high as you claim (at the evaporator) you should get your unit checked.

I don't doubt that something might be improved, but it's the numbers that puzzle me. 40 degrees is much colder than the air in my fridge, and far, far greater than any a/c unit I've ever seen. This evening I tested both my house a/c units, a friend's house a/c, and the ones in each of our cars. All five of them yeilded air between 60 and 69 degrees, when set to maximum and allowed to run for a few minutes. Does the Hummer have a uniquely huge system of some kind?

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