A/C not cycling off

I just installed A/C from a 91 into my 90, all new o rings and vacuumed it and then charged it. It is blowing cold 35 degrees at the center vent, but the compressor does not cycle off. When the A/C is set to A/C the compressor is on the whole time.

After searching It sounds like half the people think this is normal and the other think it is not.

Should I be worried or just run with it?

See if it cycles at a lower setting (such as non-recirculation on low fan speed). In my 2001, the compressor is on 100% of the time when in recirculation mode, regardless of fan speed, but cycles as needed in other modes (cycles less with lower fan speeds on non-recirc modes).

Yea After taking it for a drive it would cycle on lower speeds so it is probably normal, it was removing a ton of moisture as it is dripping like crazy when on.

Sounds Normal, its a combination of things but the key is the low pressure switch. If its hot enough and you have the AC on your and pulling enough hot air through to drop the temp of the refrigerant (thus powering its pressure) the low pressure switch will tell the compressor to stay on. if your pulling cooler air or not as much air the pressure drop will not be as much so the low pressure switch will tell the compressor to turn off.

On some vehciles when on MAX A/C since the compressor is on all the time you may get the High pressure switch turn off the MAX or recirculation function because the high pressure switch trigers that off.

I have a new pressure switch you think it is worth swapping? I believe it can be changed without losing pressure.

To change the switch you have to EVAC the system. you AC is working fine, I wish my system was in your situation. if it aint broken dont fix it.

Not sure how relevant this is, but on my 2001 the switches screw down onto little schrader valves, so no evacuation is needed.

After re-looking at the part, looks like they might on mine also... either way, i would not replace it... your AC is working and blowing cold air. As long as your charge levels are right and you are getting cold air you should not need to worry about how the compressor cluctch cycles.

So last night I put a little more r134 and it is working much better, even cooler than before and I can run it on low so it cycles.

I am guessing I was under charged so it was having a hard time building pressure.

The off cycle is actually longer than the on cycle now.