Newbe with some questions.

[FLYTYM]

I've got a 1991 ZR-1 Corvette that I'd like to top off the A/C system. While it blows cold I feel it could do a little better,I'd like to check the pressure in the system but haven't got a clue. I work on my own cars,even done front end alignments but have never messed with the A/C system but now that one more page I need to look into. Finding R12 is easy enough,I have one can of 14oz but don't have the gauges or hoses. Is it possible to check the pressure in the system and where exactly would I find the correct fittings for the Shrader valve for R12? Thanks for any and all tips,greatly appreciated.

[JohnHere]

Corvettes aren't known for effective air conditioning mainly because of mediocre condensing. That said, you can check the sight glass yourself for the presence of any bubbles with the A/C system engaged and the engine set to about 1,800 RPM. If you see any, chances are that the system is low on refrigerant. Therefore, you can "top up" the system with R-12 until the bubbles just disappear, then stop charging. Topping-up is an acceptable procedure with an R-12 system that also has a sight glass.

Attaching a Manifold Gauge Set (MGS) to the service ports while you're charging it is also a good practice so that you can monitor the pressures. Place a thermometer in one of the center dash vents so that you can monitor the temperature as well.

Call or write to Tim at ACKits.com, this Forum's sponsor, to see whether he can locate a MGS, hoses, and fittings that will match-up with the R-12 fittings on your car.

Presuming everything else is working as it should (blend doors, compressor, blower, other hard parts, etc.), and with a full charge, that's probably the best cooling you'll likely get out of this system.

The specifications that I have for your car are as follows: 36 ounces net weight of R-12, and 8.0 fluid ounces of Mineral Oil. As always, if you have an under-hood decal with differing specs, the decal takes precedence.

How much mileage has this car logged?

[FLYTYM]

Corvettes aren't known for effective air conditioning mainly because of mediocre condensing. That said, you can check the sight glass yourself for the presence of any bubbles with the A/C system engaged and the engine set to about 1,800 RPM. If you see any, chances are that the system is low on refrigerant. Therefore, you can "top up" the system with R-12 until the bubbles just disappear, then stop charging. Topping-up is an acceptable procedure with an R-12 system that also has a sight glass.

Attaching a Manifold Gauge Set (MGS) to the service ports while you're charging it is also a good practice so that you can monitor the pressures. Place a thermometer in one of the center dash vents so that you can monitor the temperature as well.

Call or write to Tim at ACKits.com, this Forum's sponsor, to see whether he can locate a MGS, hoses, and fittings that will match-up with the R-12 fittings on your car.

Presuming everything else is working as it should (blend doors, compressor, blower, other hard parts, etc.), and with a full charge, that's probably the best cooling you'll likely get out of this system.

The specifications that I have for your car are as follows: 36 ounces net weight of R-12, and 8.0 fluid ounces of Mineral Oil. As always, if you have an under-hood decal with differing specs, the decal takes precedence.

How much mileage has this car logged?

The car has 25,000 original miles. I found a set of gauges,charge hose and fittings for R-12 on Amazon. Thank you for the info,greatly appreciated.

[Cusser]

Your 1991 GM will need an adapter for the high side fitting, as government required smaller fitting on high side by then to minimize hooking up R-12 service gauges incorrectly, like Gomer did.

Of course there was a Ford-type adapter (Ford, Mazda) and GM adapter (GM, Toyota).......