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O Ring sizes for R134 port couplers?

FOMOCO on Tue April 02, 2013 1:05 AM User is offline

The last use tore a small flap in the O ring in my low-side R134 coupler. No big deal I thought, I had bought some spares for both the high and low side couplers from a Ebay store front some years ago. But when I pulled the old O ring out and compared, I found that the replacements are the wrong size. Just looking at the low-side coupler for the moment, this is what I measured with a vernier caliper (all measurements in inches):

Proper O ring: Inner Diameter = .395 Cross-section = .095

Wrong O ring: Inner diameter = .410 Cross-section = .056

Are the R134 coupler O rings standardized? i.e., is there only one size for any brand of low-side coupler, and only one size for any brand of high-side coupler?

Are they Metric or inch?

That .095" cross-section I measured on the original O ring is just .00125 from 3/32" (.09375), so that is within my measurement error, so it COULD BE a 3/32" cross-section O ring.

For the .395" diameter I measured, well 7/16" = .04375, way too big, going to 32nds then 13/32 is .40625, that is 10 thousandths too big, wouldn't think I'd be off by 10/1000 when I measured it! To get closer I would have to knock off a 64th, 25/64" is .3906, but now almost 5/1000 low. Not lining up the best on diameter, or I'm being too picky.

I Need help with coupler O Rings!

AutoCool on Tue April 02, 2013 11:13 AM User is offline

I know exactly what you mean, very frustrating. I've had couplers from a few different companies, and they're not very interchangeable at all. The only "economy snap" style couplers I've had are from Mastercool and those orings are not exchangeable with their manual ones with a thumbwheel. Other brands like CPS have a different size whether they're brass or chrome. It seems the only cross branding that will fit correctly is when they're actually made by another company, for example my Ford Rotunda valve core removers are actually made by Robinair.

Best bet is to find out what brand couplers you have, and order spare orings from/for them. When you go and try to match, and remove the oring then you probably just stretched the one you just tried.

Metric or inch? I think only the manufacturer knows and they don't list specs anywhere, just sell as parts. Same ID but thickness and OD is NOT universal between brands. You're not being too picky.

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