AC Compressor Cycle too short

[1990new]

The AC is out on Nellie until I get the system flushed out and a remanufactured compressor installed.
Trixie's ac works but the compressor does not remain running long enough during the hot weather.
I hooked up the manifold gauges this afternoon and the readings are go to Low 30 and hight 225 but
the compressor doesn't run long enough to bring the vent temperature lower that 60 degrees.

This is an 89 automatic efi car with factory installed AC converted to R134a. Before I converted
the system (replacing the compressor, receiver dryer and expansion valve) it cycled ok with the Freon.

I'm sure this is not a refrigerant charge or bad compressor issue.
Can anyone give me some tips on how I can get the ac clutch to remain engaged longer?

[itstock]

one of your pressure switches is bad, hence not allowing it to stay on long. I would think it would be the hi pressure switch.

Chad

[1990new]

one of your pressure switches is bad, hence not allowing it to stay on long. I would think it would be the hi pressure switch.

Chad

Ok.. The switch in the high pressure line on my 89 has two connectors. I pull off the plug and put a jump wire on the connector wire contacts. I start the car and turn on the air. It still continues to cycle the same as it did before. I think that I can assume from this that the high pressure switch is not the problem.

The ac on my 90 LPlus has a high switch in the high pressure line with 4 contacts.
I have a 1993 electrical and vacuum troubleshooting manual and it references only 1 refrigerant pressure switch.
Can I assume the 89 is different? The 89 with atx and efi seemed to be a unique animal in many ways.
Anyone have a vacuum and troubleshooting manual for one of them?

[FestYboy]

The low side switch cycles the clutch, the high side line pressure isn't high enough to trip the high side switch. Add 4-5 oz of 134 and see if you can't get the low side to stabilize at about 35-40. That should help with the short cycling.

[1990new]

The low side switch cycles the clutch, the high side line pressure isn't high enough to trip the high side switch. Add 4-5 oz of 134 and see if you can't get the low side to stabilize at about 35-40. That should help with the short cycling.

Refrigerant capacity wasn't the problem after all.
Turns out the cable that connects to the thermostat switch was not connected and the lever was all the way back like it would be when the heat cold lever was on heat. When you have the AC on and your move the lever gradually over toward the heat side it prevents the clutch from engaging as long. At first I didn't see that the cable was not connected and I jumped the wires as
you can see in the photo. This worked great and I let the system run until the temperature coming out of the vent was constantly less than 45 degrees. I decided this would fix the problem. When I went back to tape the splice and secured the wires, I found the disconnected cable.
I put the wires back on and connected the cable, put the lever all the way to cold and sure enough the AC started working like it should.
I was going to post a picture of my splice showing how I fixed the problem. Thankfully I was spared the further humiliation of someone on the forum pointing out the disconnected cable... sort of like fixing a computer by plugging in the power cord.
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