dpuckett

I have been putting off spending the money to have my AC system evacuated and recharged, but finally did it last week. I had to open the system to install my 2ndGen intercooler. WHile I had it all apart, I installed a new filter/drier, then had a local shop evacuate the system. I charged the system with 2 cans of Duracool, bringing my low side pressure to 40psi at idle, 30psi @ 1200rpm. I thought this was enough, but could it hav ebeen too much? I bled some out, then it definitely wasnt cooling. I added most of a 3rd can, bringing my low side up to 30psi at 1200rpm. I am not going to do any more to it til I get some better ideas. The FSM is kinda vague on what RPM to run when charging, and if there is a difference from gas to diesel.

So, I have been told that lower pressure is good (to a point) for cooling, but doesnt seem to be true in my case.

1. WHat RPM do I need to run the engine at to charge the system?
2. What pressure should I shoot for? The FSM gives a range of ~26-45psi at 100deg ambient temp. That is quite a range.
3. Is there something else I should have changed/ flushed when I had the system evacuated?
4. I'd had it charged with 134 to check for leaks earlier this summer, and found no leaks with the tracer dye.
5. High pressure side is ~150psi with the 25psi idle pressure. Havent checked it with the engine at a higher idle speed, though.

I have checked all the electrical stuff, and the compressor is engaging. I have the cycling switch bypassed for now, though it seems to be functioning under normal circumstances when hooked up.

I am at a loss for now. Where do I need to look next?

Daniel

wannadiesel

How much crud is in the heater box?

My truck (on 134a) is marginal in traffic when airflow over the condenser is low, but cools well at road speed. Have you tried it on the road or just idling in the driveway.

dpuckett

It does get better with speed down the road, it is livable if I keep the fan on high (has relay on HIGH setting, so it really blows). Once I get stopped, it warms fast. Still cant compete with the g/f's 04 Dakota, which is marginal, in my opinion.

Evaporator box is clean. I made hole and checked it out last spring. Previous owner burned off the downpipe and "had" to drive it 200mi that way, so all that stuff is pretty new.

Daniel

90firstgen

Ideally, what should the high side run at idle?

RuralCruiser007

The problem asking what pressure you should have on the high side, it depends on ambient temperature, and relative humidity.

To check the charge of your AC system you have to look at the top of the reciever/dryer and watch the flow of freon going through. If the charge is right then you will see the freon flowing all the time. (It has to many years since I have worked on these systems) HTH

90firstgen

Let's say 90 degrees ambient and 30% humidity.

fordsrbetter

going to be at least 225-250 high side at 1200-1500 rpm low side anywhere form 40 and lower

90firstgen

My high side was at 200 on idle in those conditions. I thought it was a little high so I didn't put anymore freon in. How much pressure difference do you think there would be from idle to your 12-1500 rpm? I know just enough about A/C to be dangerous. Filling at idle, ideally what should my high and low side be at 90* and 30% humidity?

12valve@heart

Durocool seems to be a unique substance. I suspect that you may be overcharged but I can't speak with any authority since I haven't had time to get my Durocool install fine tuned yet.
I evacuated and recharged mine by weight last year when I fixed a leak but then I blew the tranny so I didn't mess with it till this year. It was running way warm until I bled it down to closer to 25psi low side during a trip. It's still too warm but I haven't had time to work on it any more.
Durocool is basically refined propane so propane charge levels should be close. Let us know where you end up.

dodgezilla04

warm the can in hot water, start the truck with ac on, allow the suction side to pull what it needs till there is a slight amount of frost on the suction pipe about 1' from the compressor. then stop filling.

FSM's are great if all components are new, no crud in system, compressor at 100%, and orifice is clean and clear.

12valve@heart

. . . and the stock refrigerant is being used.

dpuckett

I checked the pressures at 1200rpm. 175 high side; 28 low side. Sounds like I am in the "sweet spot" (maybe a little low on the high side) but still not as good as I expected.

Is there anything else that could be causing my problems? Is there a way to recover the propane I have in there, if I need to evacuate the system again?

Thanks for the help, guys.

DP

97catintenn

I think you should keep adding coolant to the system till you get your high side up around 200. Your low side will still be at or around 28psi.

90firstgen

How much high side pressure is too much when youre idling? I think my system needs more refrigerant but seeing 200 high side at idle has me scared.

pred

If you idle your truck with ac on max, and fan on high, and there is a 30 to 40* differance between the ambialt temp (in shade) and the air coming out of the vents, This is all you are going to get using anything but R12 or straight propane,,,,, Tint the windows and be happy.
I still run R12, And on a 90* day, Parked in the sun my vents are pushing 38-40*f,, But this is old made of gold R12,
Seriously, If there if a 30 to 40* differance, You are doing okay!
Peter.