1999 Ram 1500 - AC blows hot when decelerating and stays hot for a while afterwards.

[SwampChuck]

This is a strange one. I'm fairly certain I have a coolant leak somewhere, but for now, when I fill it I notice that it blows nice and cold but will get warm as I decelerate. It almost feels like fluid in a pan is moving forward in the pan when decelerating, but I know that's not how AC coolant works. The compressor clutch stays on. Once this hot air happens, the AC won't blow cold again for a while, perhaps 3 or 4 minutes. Then it will start working again. The truck is a real ****** and I barely have a dash for it to blow cold air through, but that cold air was one last saving grace for the truck in the 95° Florida heat.

Thanks for tips.

 

[RodeoRam]

A few things come to mind. First, a compressor clutch continuously engaged is a sign of low freon or a bad clutch. A short-cycling clutch would be low freon, too. Second, if you hear fluid sloshing when accelerating/decelerating or turning, you may have a plugged A/C condenser drain. The condenser box can get so full you'll have water running out of the floor heater vents onto your feet or your passenger's feet depending on which direction you turn. Pretty easy fix for that. Third, the delay on getting cool air again could be a check valve and/or blend door/actuator problem.

The A/C on my 2001 while accelerating would shift from the dash vents to the defrost vents and then switch back to normal when I let off the accelerator which was a check valve issue from what I've read. That's not exactly your problem, but it shows how a check valve can mess with stuff. I also had to have the blend door replaced because the plastic on the door where the actuator connects had broken. An open blend door allows outside air into the HVAC system and thus the cab making it seem the A/C is not working.

 

[Bear_Gibson]

First, get yourself a set of R134 gauges. So much can be diagnosed from gauges. Also, My 99 had a similar problem where unless you were moving the a/c wasn't very good. Turns out that the old fan clutch was worn out. The truck never overheated, but you could never hear the fan in the mornings when first taking off. It never occurred to me it was weak until I put the new one on.

I put a short clip of the fan clutch I'm talking about on youtube.

1999 Ram fan clutch that kept the engine cool, but not the a/c.

1999 Ram fan clutch that kept the engine cool, but not the a/c.

youtu.be