A/C Overpressure... or not??

[jrollf]

A/C gurus, looking for your help/input.

Out of the blue today, while idling, twice the over pressure valve on the compressor dumped refrigerant like the system over-pressured, the 2nd time was right after pulling into my driveway and idling for maybe 30 seconds. Popped on the gauges, and everything is in the normal range (both high and low) for the temperature / humidity outside, low side was a bit low but low but within range... For the temps the low side was at the lower end of the pressure range per the chart, but the high side. Outside temps were 85 degrees and about 40% humidity.

While my truck is a '93, the A/C system is 100% almost new 1994 R134 setup. A couple years ago I replaced EVERYTHING with NEW, compressor, evaporator, condenser, hoses, dryer, pressure switch, etc. It's an actual R134 system based on 1994, not a "conversion", the hoses even have the factory R134 connectors. Nothing was reman/rebuilt, all new. Also before anyone asks, I'm not using a variable orifice, so a "stuck" orifice tube wouldn't be the problem. After the initial charge when I rebuilt the system a couple years ago, I've not added any R134 to the system. I good vacuum was pulled on the system when it was charged.

Only thing that has changed recently is I just put a new "heavy duty" fan clutch on it... based on sound alone it is moving more air than the one I removed from the system. When I was under the hood with the gauges on, the fan was moving a lot of air, even at idle.

Thoughts? The system survived the heat of Houston Summers for two years... Could the over-pressure relief valve "just go bad"?

Thanks!

 

[gnathv]

Have you looked at your condenser for junk blocking it?

 

[jrollf]

Have you looked at your condenser for junk blocking it?

Condenser is pretty clean, few stray bugs but otherwise clear and clean.

I did find one maybe cause... I found the low pressure return hose was getting pinched between my air cleaner and the hood***. Maybe it was enough to reduce flow and build pressure on the high side acting like a clogged orifice tube would, but then was perfectly fine when I had the hood open with the gauges on it. Fingers crossed this was the issue.

My concern now, is I have no idea how much PAG oil was blown out of the system. The only "correct" way to fix it is evacuate the system, flush the entire system, and replace the dryer/accumlator and start from scratch... I really don't want to do all that.

***I have a Banks Sidewinder, I recently had the air cleaner assembly off the truck doing unrelated maintenance and didn't catch that when I put it back on, the hose went over the air cleaner assembly instead of behind it.

 

[gnathv]

A little oil spraying out the valve looks like a gusher. Probably an ounce or less was lost.

 

[riphip]

IF you decide to evacuate and recharge, check the screen on the orifice tube. Some NEW condensers being sold are not properly flushed after assembly and have left-over junk in them. I flush anything new now with non-chlorinated brake cleaner & high pressure dry air 3 times before install.