Strange a/c problem - Dodge Cummins Diesel Forum
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post #1 of 5 (permalink) Old 07-12-2019, 06:29 PM Thread Starter
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Strange a/c problem

My a/c is acting up, it cools but it takes 15 miles or 15 to 20 minutes to get there!!! I have a thermometer in the vent, it will get down to 55 to 57 degrees. I checked the freon and it is fine. Replaced the compressor and dryer and some lines 4 years ago(about) Got a leak and replaced the evaperator core last year. The only thing I havent replaced is the condenser. Any ideas or help is appreciated. It also seems to blow colder when I am on a back road going slow?

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post #2 of 5 (permalink) Old 07-12-2019, 08:55 PM
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It's probably taking the 10 to 15 miles for the fan clutch to catch. If I first leave work and hit the stop light within 5 miles of my office, my ac pressure will sky rocket and the high pressure switch will cut the compressor out. I live in PHX and it was 113 today. If I get the green light instead, the truck will get up to temp and the clutch will kick in so the pressure never gets up. Theoretically, you could replace the high pressure switch, install a trinary switch and wire a electric pusher fan which would kick in such instances. The fan wouldn't be on during highway speeds.

I've never done that because I'm too lazy to care and my ac gets really cold after so it would only be useful for that first few miles.
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post #3 of 5 (permalink) Old 07-13-2019, 08:14 PM
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Sounds low on fluid. Have it professionally checked at an AC shop. They do not charge much to check and charge.

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post #4 of 5 (permalink) Old 07-17-2019, 02:51 AM
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Last time i measured my vent temps, was on a day in the low 90s, direct sun all day, idling...and 45F at the center vents.
2017 company Ram was 42F at the vents, parked right beside me.
You system definitely is not at optimal performance

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post #5 of 5 (permalink) Old 07-17-2019, 04:01 AM
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Run it and see if you can hear the ac Clutch locking up.

If it's kicking in/out there's two causes. Either you are low on refrigerant and the pressure switch is forcing it to shut off, or the filter/dryer is plugged and freezing up. Give it seems to cool better when going slow I'd lean towards the filter/dryer end of things.

To also note, a system that is overcharged will freeze up intermittently as well. There is a temp sensor on the filter/dryer for that very reason.



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