I am brand new to this site and thought I would try it out and see if I might get some help on my Dodge Truck. I just reworked the entire air conditioner system in my 89 Dodge Cummins and it don't blow as coll at 65-70 mph as it does at idle speed. The guy worked on my system put three canisters of r-134 refrigerant in it. Is that too much or not enough? It does blow cooler air at higher rpms but it doesn't seem to be as cool as it is at idle speed. Can anyone help? Thanks in advance!

 

I live in FL where the outside temps are already a bit warm. So keep that in mind when comparing temps.

I can get about 57F out of the center vent once the system has cooled down the truck a bit. I get about a 30-35 degree difference between the cab temp and the vent temp. Eventually the lowest vent temp I will see is 57F or so during the day with the Florida sun shining in the cab. This is the same driving or idiling.

I can't remember how much I put in since I have the manifold/guage set and added till I saw the pressures I wanted. I think the conversion spoec is 32-36 oz. If I remeber right my pressures are 35 low and 275 high.

The low side will increase in pressure until a certain fill is acheived and then it will start settling back down as you add more. This makes it hard when your adding refrig. cause you think your putting in too much if your looking at the low side pressure. Especially using one of those parts store guages on the can or the hand held deals.

Also the AC compressor should be cycling once it starts blowing out cold air. The switch on my 91 will start cycling on and off quite a bit. This is to keep the system from freezing up. There's a sensor(copper probe) that goes in a port on the line.

I replaced everything except for the compressor and the evaporator in the dash. Also flushed the compressor with mineral spirits, used new PAG oil and pulled vacuum on the entire system.

Set on Max air the air temps coming out of the vent should stay consitant. With the controls set on just AC you might see the temps rise since it's pulling in outside air as you drive. The temps on mine with outside air rise quite a bit. I keep it on max all the time.

Only other thing I think I might change on mine is the expansion valve. There is a special order valve that is meant to be used on a conversion. My guess is it changes the oriface size for use with the 134. This might solve the cycling because the system is getting too cold in the lines.

Here's what I use for temps

Den