Here are the details: 85 F150 w/ 300 I6 and 4spd trans, Duraspark II setup.

I just replaced my AC compressor, and want to confirm I'm on the right track before putting any more freon in it. The PO had already switched it to R134a, so it was running fine on that before the compressor went out. Upon beginning to recharge the system after making my repairs, the compressor clutch didn't engage right away, then as some freon started to get into the system it began engaging and disengaging really quickly (on for maybe a second, then off for a couple). As the pressures started to rise, the clutch was staying engaged longer.

Now, after 3 small cans of the stuff, my pressures are reading about 40psi low side and 220psi high side. According to the R134 pressure/temp chart, I should be at about 50/315 in my neck of the woods. What concerns me about adding more freon is that now the compressor clutch stays on constantly...it isn't disengaging at all when the AC is on, though the pressures stay steady.

Is this normal? I had thought perhaps it was because the pressures were still low so it is staying engaged trying to bring them up, but that wouldn't explain why it was on and off as the pressures were first rising. The air is getting colder, but definitely not back to where it was.

Thanks for any help!

 

I think you need more gas. Initially the clutch didn't come in as there is a low-pressure switch that doesn't let the compressor run if the system is very low or out of gas. Once you get enough to close that switch the compressor comes on, but only briefly as the low-side pressure drops as the compressor pumps the gas out, and the switch opens.

Eventually you get enough gas in the system that the switch stays closed and some cooling starts. But, as the gas level is low you never get full cooling until you put in more gas. So, keep charging the system - assuming you pulled a vacuum on the system after installing the new compressor. Did you?

 

I did pull vacuum on it beforehand. My compressor couldn't quite keep up with the vacuum pump so I didn't run it for a full half hour, but I did have it on a vacuum as long as I could.

Thanks for the input...looks like I'm buying a couple more cans of refrigerant

 

I don't think I would put more than 3 12oz cans in it. There should be a sticker somewhere that tells you how much r12 it originally took. They usually run fine with 2 1/2 cans.

 

That's what had me concerned. I just finished topping it off tonight. I put in 5 cans total, which seemed like an awful lot, but my pressures are good and the air is nice and cold. However, the compressor clutch is still not cycling on and off...just stays on all the time. It's not overheating the truck or anything, but I don't wanna burn up my compressor. Any ideas?

 

The compressor will not cycle on and off on a hot day. Only on cooler fall days will it cycle. It's perfectly normal for it to run continuously.

If you put 5 12oz cans in it, I am surprised the pop off safety valve hasn't blown on the compressor.

 

I'm not an expert on AC systems, but if your pressures are where they should be given the outside air temp, then I think the system is properly charged. And the fact that it is cooling properly confirms that. I can't explain why it too so many cans, but perhaps you had a leak while charging?