[rbowman]

Well after three years of putting it off, I'm finally getting around to fixing the air conditioner on the 77. I have power up to the pressure switch but have to use a jumper wire in order to get the compressor to kick in, it won't engage without the jumper wire. When I started I didn't have any power at all. what would cause this?

[charleyahrens]

Originally Posted by rbowman

Well after three years of putting it off, I'm finally getting around to fixing the air conditioner on the 77. I have power up to the pressure switch but have to use a jumper wire in order to get the compressor to kick in, it won't engage without the jumper wire. When I started I didn't have any power at all. what would cause this?

One possible cause is low / no freon in the system.

[rbowman]

Ok so it off to the A/C guy? How, if at all possible, can you tell if it's been converted?

Ron

[toobroketoretire]

Originally Posted by rbowman

Well after three years of putting it off, I'm finally getting around to fixing the air conditioner on the 77. I have power up to the pressure switch but have to use a jumper wire in order to get the compressor to kick in, it won't engage without the jumper wire. When I started I didn't have any power at all. what would cause this?

When you flip your console selector switch to the A/C position that sends current to the A/C clutch relay (mounted on the heater housing above the passenger's feet) which then sends current thru the low pressure switch and then to the compressor's clutch. The fact you have to jump across the low pressure switch tells you your system needs more refrigerant as it takes 20 psi to close the switch.

"At rest" (engine off) the system should have approximately 75 psi in it so check out your pressure before starting your engine and if it shows less than 75 psi you'll have to put more in. And don't forget to use refrigerant with oil in it as oil leaks out at the same time the refrigerant does.

[toobroketoretire]

Originally Posted by rbowman

Ok so it off to the A/C guy? How, if at all possible, can you tell if it's been converted?

Ron

If it has been converted by a professional it'll have different fittings on it that aren't compatible with R-12 gauges and hoses. I converted my '71 over to R-134 but rather than changing the fittings I elected to alter my R-134 can adapter to work with my R-12 gauge/hose set so I can use my R-12 gauge/hose set for both types.

[rbowman]

Sorry for so many questions, This is the first time I have ever worked on the a A/C system. So how many cans would it take to completely fill a system?
I did find a receipt from the previous owner where he had it converted to 134A about 4 years ago. A shop did do it so I am assuming it was done correct. The air never worked when I bought it. Got power everywhere I need it and the correct lever position so I figure I've got to be close. If I can get it to work I will have to take it to a shop to find a leak. I did find someone with gages.

Ron

[fishslayer143@yahoo.com]

connect the gauges and see if there is any pressure in the system at all.. if not, then its gonna need some work before recharge ..if the pressure is just low, you can add to bring it up to engage the compressor .. then see what your readings are ....rule of thumb is ambient temperature X 2 +50 on high side and 30-45 on low side

[rbowman]

Got the vette into the shop to add freon and found the compressor leaked, Replaced compressor and added oil and held pressure so added freon. had cold air but on the way home the compressor started locking up, put in 3 pounds of freon, any idea?

[fishslayer143@yahoo.com]

how long did you evacuate the system for , and did it pull down to 30 hg?did you replace the drier? is yours a radial type R4 compressor?, did you change the orifice tube? you may still have moisture in the system

[rbowman]

Did vacuum the system, not sure how fare they pulled it down, The system was already converted to 134. Might have to re-vacuum the system?