Air Conditioner Compressor Cycling

[magik235]

I converted my AC from R12 to R134 4000+ miles ago. I have a 1985 350 with California emissions. It is still blowing cold air but the compressor keeps cycling on and off at frequent intervals. It has done this since I got it working again. The pressure is in the prescribed range. Is this normal? Any suggestions for improvement?

 

[black dawg]

What pressure is it shutting the compressor of at? What is outside temp?

 

[imiceman44]

I converted my AC from R12 to R134 4000+ miles ago. I have a 1985 350 with California emissions. It is still blowing cold air but the compressor keeps cycling on and off at frequent intervals. It has done this since I got it working again. The pressure is in the prescribed range. Is this normal? Any suggestions for improvement?

well with mine it does that too when it hot outside so I don't know what to tell you.

 

[496truck]

That is what an A/C system does. It cycles to maintain proper pressure.

Cycling too fast can be signs of a problem.

Cycling too long can be signs of a problem.

All comes down to pressures.

 

[British Slave]

You could be low on refridgerant or the low pressure switch may be bad. Most likely low on refedgerant. When the pressure on the suction side drops below about 30 lbs, the low pressure switch cuts the compressor out to prevent damage.
A quick check is to put a jumper in the low pressure switch connector and start it up if the compressor runs ok without cycling, it's low on refidgerant. BUT DON'T LET IT RUN WITH THE JUMPER MORE THAN A MINUTE OR YOU MAY TRASH THE COMPRESSOR.

 

[Blue85]

Well that's what the switch does - it keeps the low side pressure in the prescribed range. The compressor will cycle more frequently as the refrigerant level gets lower. If it won't stay on for more than 10s, you are either low on refrigerant or have a blockage. Sometimes the orifice tube plugs with junk and the low side pressure drops really quick as soon as the compressor comes on. If the system is still cooling, then probably not. If it's mega hot, you're parked and the blower is on high, the compressor should stay on continuously, as long as the pressure doesn't drop to freezing.

Is the low side line getting cold all the way to the compressor?

 

[British Slave]

Well, that's what I said. ?????????????????????????????

 

[magik235]

Thank you for the information. It was extremely useful. I put the pressure gauge on the air conditioning and watched it as the compressor cycled. It was going off on the low side when the pressure hit 20. I added 14 ounces of coolant and now it stays on like it should.

 

[imiceman44]

Thank you for the information. It was extremely useful. I put the pressure gauge on the air conditioning and watched it as the compressor cycled. It was going off on the low side when the pressure hit 20. I added 14 ounces of coolant and now it stays on like it should.

Oh I had assumed you checked the pressure when the A/C is running.