Rear Air Issue - Solved.......
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Elder User
Joined: Aug 2003
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From: Houston, TX
Rear Air Issue - Solved.......
First off I would like to thank all of the contributors to my original thread on my Aux A/C problem. I want to especially mention 99f350sd. He mentioned that the high side should get cold at the orifice tube. I did not know that. I thought as long as the entire tube was sweating everything was ok and the problem was in the evaporator.
Well, it turned out to be a plugged up filter/drier (whatever that bulb looking thing is). It was just letting enough refrigerant through to vaporize and make the tube sweat. The pressure apparently was not enough to traverse the orifice tube and cool the evaporator. I took the hose assembly out of my '90 and replaced it. Now the rear vent temps are just as good as the front. 51 at idle and 30 at freeway speeds.
Again, thanks to all the contributors; my grandkids are especially grateful, they ride back there.
Klaus Cook
Houston, Texas
Well, it turned out to be a plugged up filter/drier (whatever that bulb looking thing is). It was just letting enough refrigerant through to vaporize and make the tube sweat. The pressure apparently was not enough to traverse the orifice tube and cool the evaporator. I took the hose assembly out of my '90 and replaced it. Now the rear vent temps are just as good as the front. 51 at idle and 30 at freeway speeds.
Again, thanks to all the contributors; my grandkids are especially grateful, they ride back there.
Klaus Cook
Houston, Texas
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Not meaning to wet on your parade but if your air is 30 degrees at the outlet, it is too cold. If it ices up and stops blowing you need to adjust your low pressure switch clockwise to raise temp. The evaporator can not run below freezing or it will freeze into an air blocking chunk. 40 degree air at the outlet would be about the coldest that will work.
Ken
Ken
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From: Houston, TX
Originally Posted by ken1mod
Not meaning to wet on your parade but if your air is 30 degrees at the outlet, it is too cold. If it ices up and stops blowing you need to adjust your low pressure switch clockwise to raise temp. The evaporator can not run below freezing or it will freeze into an air blocking chunk. 40 degree air at the outlet would be about the coldest that will work.
Ken
Ken
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It depends on the weather. If it does not freeze up, no big deal.
If your thermometer is accurate, and you do have 30 degree air, you have a 20 degree evaporator which is too cold.
Pull off the connector to the low pressure switch on the accumulator. You will see a slotted adjustment. If you turn this clockwise, the pressure in the evap will rise. It is easy to adjust.
Too cold an evaporator also wastes a bit of fuel as the compressor runs more.
Ken
If your thermometer is accurate, and you do have 30 degree air, you have a 20 degree evaporator which is too cold.
Pull off the connector to the low pressure switch on the accumulator. You will see a slotted adjustment. If you turn this clockwise, the pressure in the evap will rise. It is easy to adjust.
Too cold an evaporator also wastes a bit of fuel as the compressor runs more.
Ken
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Joined: May 2003
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From: Lyndonville, Vermont
Ya you would need a low pressure of 20 psi to get that cold..I thought you said it was 60 psi. 40 deg is about as cold as it gets on r134a. The old cadilacs i used to work on would blow ice at you...
Dick
Dick
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I would tend to bolster Klaus's findings. My conversion runs around 32 degrees center vent at highway using the same type thermometer. I just assumed because it was a cheapo thermometer, it was off a few degrees. But it does run really cold when using just the front system. When the rear is turned on, the front temps are higher, around 38-40 degrees (highway). The front unit throws a bunch of condensate but hasn't frozen yet in 4 years of service.
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Elder User
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From: Houston, TX
Originally Posted by 99f350sd
Ya you would need a low pressure of 20 psi to get that cold..I thought you said it was 60 psi. 40 deg is about as cold as it gets on r134a. The old cadilacs i used to work on would blow ice at you...
Dick
Dick