A/C pressure release valve

i put 2 cans of r134a in each of my 99 and 2000 Cherokee 4L.
it was about 100degrees and according to the chart i was supposed to get around 55psi on the low side.

well the 2 cans put them up to about 50psi, which is good enough i guess.

however, on the 99, the next day when my wife put the A/C on, when the compressor kicks in, the pressure release valve is venting refrigerant... loud popping noise, and shooting oil al over the distributor cap and wires.

i assume i added to much... but before i take it to an A/C shop... can i just fashion something to direct the blast of oil/refrigerant down to the road and let it vent until it stops venting? or is this something that i need an A/C shop with the proper equipment to take care of?

thanks...

on the compressor there should be a rating plate with the proper amount in ounces of refrigerant im unaware of a blowoff valve sounds like perhaps something blew due to excessive pressure

and for what its worth intentional venting of refrig. is illegal

Let's not get into the undocumented and overregulated R12/R134a issue - as there is NO Freon police or even local enforcement to bother with it anyway. It's just a feel good law.

Venting from the system as described is a defect. Have the valve inspected and repaired. Using a chart and pressure gauge is a good deal better than most folks I've seen in the parking lot - many of whom overfill the system, or vent the can to the air when returning our fill hose. If they remember to run the A/C while filling, I consider it a success.

Patrolling for A/C releases? I can't get the cops to patrol the lot for engine repairs, which is banned, too. More important things to do.

I don't think there is any "pressure refief valve". THere is a high pressure side fitting and a low pressure side fitting. They are just like Schraeder valve like tires have. They should also have a cap on them almost like a valve stem cap, except these are special refrigerant compatable pieces. The plastic standard caps aren't worth a damn. A refrigerant service place can sell you some brass ones that will prevent leaking better.

yeah, there is a pressure relief valve.. i looked it up in the Service Manual.
its right on the back side of the compressor... and when it opens due to over pressure, it blasts the side of the engine with oil/refrigerant mist.

the manual says its not serviceable...

i'm not running the A/C until i find out what to do about the venting...
according to the manul, when the over pressure situation ends, the relief valve won't open.. so maybe i just need to let it pop open for a little bit until its satisfied the pressure isn't to high anymore. it sounds like a machine gun going off...

Usually 2 cans would be a lot to be adding. Do the newer Cherokees have a sight glass like my '87 and '89? If they, do you should monitor that to know when to stop adding refrigerant. If you don't have a sight glass, I'm not sure how you can determine the proper charge unless you evacuate the system and start with it empty.

I am having the same problem,(spraying out the pressure relief valve on the back of the compressor).
What was the resolution to your problem?
Reduce the amount of refrigerant in the system?

Probably ought to have your refrigerant recovered by a machine at a shop and then have the machine add the proper amount back in.

50lbs at idle on a 100* day doesn't sound too far off, but you definitely have either too much refrigerant in there, or have a blockage in the system. A manifold gauge set would be necessary to determine what the high side is doing.

24oz of refrigerant is an awful lot to add to an operational system, but not more than an empty system should hold.

In the era of cell phone cameras, I don't recommend atmospheric venting of refrigerant-- it only takes one nosey do-gooder to ruin your day.

Our AC systems only use 1.25 lbs (20 oz) of refrigerant. Two cans threw you to 24 oz, plus whatever was already in the system. Definitely an overcharge.

Not sure what the charge recommendations are for the earlier XJs, but for the 97-01; the factory recommended R134a charge is 1.25 lbs or approximately 20 ozs.
The best way to charge a system is to either charge by superheat or pump the system down into a vacuum of 29"Hg and meter in the factory recommended charge.

huh, never paid attention to the capacity of the newer ones-- '88 said 36oz of R12, so roughly 28-29oz of R134a is what I was figuring-- never mind, I'll go back to sleep now.:speepin: