My daughter has an 88 XJ 4.0. We just charged the A/C system using 36oz of R134. It was completely empty. Anyway it works great, super cold but the compressor runs continuously. I’ve read that it could be overfilled but when we started the recharge as soon as the first bit of refrigerant was in the system the compressor turned on and never turned off, ever, so I’m not sure it’s over charged.

I just changed the A/C thermostat and also replaced the A/C relay.

Manually turning a/c on and off here are the pressures. It’s about 80 degrees outside.
On.
Low side 11
High side 180

Off
Low side 30
High side 145

According to my manual, normal operating range.
Low side 24-50
High side 160-250

 

On those early systems, they had thermal expansion valves as a metering device. They are very forgiving about how much refrigerant is in them. The way you charge those is with the sight glass located on the accumulator. When it is running you should see the refrigerant running past it. If you cannot see some bubbles or a fog running past, then it is overcharged. The other thing is that on a TXV low side measurements are useless. If you want to get it right on the money you use sub cooling measurements, which is the high side temp on the gauge minus the physical temp on the discharge side of the condenser coil. But the sight glass method is easy and pretty accurate

 

Did you put the system under a vacuum, before you put the converted R12 / R134a in? Was it a 36 ounce can, or did you correctly weigh the amount of freon you put in?

 

I put a vacuum on the system for about an hour, then closed it up and let it sit for about 45 minutes and didn’t see any movement in the gages. I used 3 12oz cans.

 

I will check the site glass but my main concern at this point is will the compressor burn up if it runs continuous?

 

The site glass shows no bubbles or fog, perfectly clear. Does it matter which side pull a little refrigerant out?

 

No, the refrigerant and oil in it cool it internally

 

It is overcharged, the system takes about 2.5 pounds. However I would probably leave it. The compressor works harder, but it won't ruin it.

 

Great. Thank you. I will leave it for now until I’m sure no leaks spring up. It blows super cold and my daughter is stoked since we’ve already had a couple 100 degree days here.

Just for my own info though, does being over charged cause the continuous running of the compressor and at the proper level it will start cycling if everything else is working properly?

Thanks again for the help.

 

No it doesn't. Most AC systems have a compressor that runs continuously. Short cycling is something that is caused by being undercharged

 

Again, thank you. Have a great weekend.