O rings. A cautionary tale

[bohica2xo]

I don't do a lot of work any more, but still help a few people. A member of the local Mustang Club was going crazy with a leak in a very stock 1995 Mustang.

He is a good mechanic, but not much experience on refrigeration. He had replaced the condenser because of a rock hit that caused a leak. Car is under 60k miles. He pulled it down and charged it. Used a scale and bulk 134a 3 days later, no cooling. I went to help him and it had 40psi static pressure - on a 90 degree day.

Grabbed my sniffer and checked the condenser springlocks. Yep. Car is a desert car, no corrosion. So I asked where the O Rings came from. His handy dandy 200 pc kit from the jungle clowns. Told him to get the right O rings and try again.

Went back a week later, and he was beginning to understand more. His vacuum would decay by 10" minutes after pump shutdown. So I shot 2 ounces of R290 in it and grabbed the sniffer. Same place, the springlocks were howling.

Where did THAT set of O rings come from? Chain autoparts store. Blister packed. Ok. Time for a field trip. Gaudin Ford is 4 miles away. "I need the condenser O rings for a 1995 Mustang 5.0" Tap tap tap. You mean these? Picture of the assembly. "Yeah. All 6 of them" No problem, back in a minute.

Bill is looking at me like I am nuts. I expected the dealer to have the parts for a 30 year old car? She comes back with 2 ziplock bags. $18.36 with tax. 5 minute deal

Back at his shop I put some Nylog on the condenser fittings and handed him the O rings. He put the seals on and started to push the coupling together - and stopped to look at me. Fits tight. Yep. Old rings just slipped together. Uh huh. Closed up the system, pulled a vacuum and it held overnight. Charged it and went home. It has been cooling great all summer. No hits with the sniffer.

With so much offshore stuff out there, and the confusion between the metric parts and US sizes, be very careful with O rings.

[Cusser]

Agree, one must use the special AC O-rings, typically green NBR.

Hardware store O-rings are for water, not refrigerant or automotive fluids.