Re: auto a/c

Posted by jdemaris on July 23, 2008 at 09:11:27 from (67.142.130.38):

In Reply to: Re: auto a/c posted by Allan In NE on July 23, 2008 at 08:21:26:

I just went through that - sort of - on a 98 Dodge Grand Caravan with front AC only with optional HVAC computerized controls.

Put a new compressor and dryer in it. The previous compressor had a slow shaft-seal leak - i.e. it wasn't trashed.

Got all done - pulled a vacuum for two hours and then charged exactly to specs - 34 ounces of 134A. Then ran it - it would blow cool air at first (cool - not cold), and then get warm after five minutes. I checked low side pressure and high side pressure against outside temps. Also checked high-line temp. All checked in-range as to the factory book. Dodge provides one of the most comprehensive charts I've seen with all pressures at all line temps, evaporator temps, and air temps.

Everything checked pefect but the thing would not cool. In perhaps a stupid bout of desparation - I added an extra 12 ounce can - and the duct air temp went down from 68F to 58 degrees F (on an 80 F degree day). I then added a second 12 ounce can and the duct temp went down to 50 F degrees. So - I got all done and it now works pretty well. It passed the computerized cool-down test. Low and High pressures with the two-can overcharge still pretty much read the same as before - with the low side slightly higher.

I've got no answer to this one - except it now works and I'm going to leave well enough alone.

I had been suspecting that maybe some of my 12 ounce cans - some 10 years old - were maybe not completely full? Well, now I doubt it. I checked one - 15 ounces full and 3 ounces empty - right on the nose.

It was running 38 PSI on the low, and 270 PSI on the high at 85 degrees F. Dodge factory manual says that at 80F - normal is : low at 17-35 PSI and high at 230 - 360 PSI. Air coming out of the AC duct should be 38F to 50F.

This one's a bit beyond me - but it's working good enough for now - especially since I'm sick of working on it.

Replies:

• Re: auto a/c Allan In NE 10:05:53 07/23/08 (0)

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