Ok I changed my r12 to 134, did all the good things & it blows cold air as long as I jump the switch at the accumulator. The thing is I pumped the system down for an hour, it held, then I charged it with 134 & the compressor kicked on & off. My low side is at 40, my high side broken ?
Any ideas, not enough freon?
I agree you need more 134a. You'll see and hear the compressor click on longer each time as the system gets closer to full and then it will finally run on it's own.
Also you might have a bad pressure switch. They're only $15. If you didn't replace it originally it might be worth it to try that too.
I had the same problem with mine. It had been not working for years, and I evacuated it and recharged it with 134a. It seemed to click on and off too much, so I adjusted the accumulator switch a little bit to help it stay on longer. If you take the elec plug off, and look between the spade connectors, you will see the adjustment screw.
Adjusting the screw helped the cooling, and it worked well at idle, but as you drove down the road, it would stop cooling. By reading in the A/C forum below, I found out the clutch on the compressor could be out of adjustment. It should have a .14 to .30 inch gap. I could put a .40 feeler guage in the gap, and still had room. So I borrowed a puller tool from Autozone, and pulled the clutch out and took one of the spacers out and re-installed the clutch. That solved the no cooling while driving down the road, and it also helped cooling at idle. The large gap at the clutch makes the clutch more stubborn to pull in, and it makes it want to slip also.
P.S. Also make sure you have the A/C controls on normal, and have the windows rolled down. I made the mistake one time of turning the controls to MAX like the directions tell you, and I had the windows rolled up. Max pulls inside air into the evaporator, and with the windows rolled up, the inside air gets colder and colder, so the pressure goes lower and lower, and the compressor will want to cut off. I kept adding freon, but I overfilled it because of the evaporator getting so cold. You want to make sure you have outside warm air hitting the evaporator when filling the system, and this will keep the pressure up and keep the compressor kicked in longer.
Now I have cold air, just not much of it, seems even at hi speed the fan puts out little air. Is there an obstruction or something dirty not allowing air flow? Is there an easy way to see if the evaporator is clogged. I removed the fan and there was all kinds of junk, leaves & dirt in the chamber, cleaned as best I could.
There is no easy way. You have to split the box apart in the engine compartment. If yours is like my 80 was, the evaporator was almost completely clogged with junk and I supposed since the evap gets wet when it's working, dirt sticks to it.
The evap plugged was not on the A/C system I described in my previous post(that was my 89) but I was contemplating getting the A/C system on the 80 working, but someone had taken a hacksaw and cut the evap pipe off. That's why I was in there. I never got around to getting the A/C working after I replaced the evap core, but what a difference in the defrost and the heater. If you have one of these trucks and think the heater and defrost system is marginal, think again. After I put the other evap core in, that system would run you out of the cab, no matter how cold it was outside.
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