A/C never worked where do I start
Thread Starter
Instructor
Joined: May 2006
Posts: 144
Likes: 0
From: Stockbridge GA
A/C never worked where do I start
I have searched but I have not found A good tread on trouble shooting or testing my A/C system. I know I have all of the elc. system working, but the vacuum system and the rest of the A/C system I know nothing about. I have also swaped my v belts for a 1995 serpentine belt system so I guess I will have to have some hoses made . Advice on this would also be very helpful
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
If you do not own a copy of the Chevrolet Chassis Service Manual, I highly recommend that you get one. Under the section on Air Conditioning, it has individual drawings/diagrams of [both] the vacuum system and the electrical system. The standard wiring diagram does not show this system in it. Read the material in this section of the manual to understand how it works. Also, study the vacuum diagram and how it interconnects with the [mechanical] control head in the shift console. Basically, some electrical contacts on the control head turn the system ON and OFF, depending on which setting you have selected. The [electrical] blower system selects the blower speed required, and the vacuum system merely selects the appropriate position for (vacuum operated) diverter doors in the plenum housing so that the airflow comes from the desired source (inside air or outside air) and the discharge air comes from the correct vents. That's about all there is to it. But you really need that manual to understand it and trace down your problems.
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
GM is known for excellent A/C systems & it's very reliable. Aftermarket are recir.only.
The vac. control system is actually very reliable.
1) The vac. line from engine can be damaged from heat - a small plastic tube that goes in below the hood alarm switch into wiper valley. Replacing most of engine side w/ hose will fix.
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease to fix.
3) If you have a heater, the small vac. tube to heater hose valve underhood probably also needs replacing. Block w/o heater.
An A/C shop can make hoses or you can do it. Are you changing to R134?
I have a different compressor that uses less hp & I made up hoses to stock A/C system.
Works great.
The vac. control system is actually very reliable.
1) The vac. line from engine can be damaged from heat - a small plastic tube that goes in below the hood alarm switch into wiper valley. Replacing most of engine side w/ hose will fix.
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease to fix.
3) If you have a heater, the small vac. tube to heater hose valve underhood probably also needs replacing. Block w/o heater.
I have also swaped my v belts for a 1995 serpentine belt system so I guess I will have to have some hoses made .
I have a different compressor that uses less hp & I made up hoses to stock A/C system.
Works great.
Thread Starter
Instructor
Joined: May 2006
Posts: 144
Likes: 0
From: Stockbridge GA
I have found a vacuum diagram and it seems that my control head, dosn't work along with all but one of my vacuum solenoids. I am wondering if there is any way to test my evaporator? To top it all off I don't think there is a piece of the whole assembly that is not broke ( nothing a little bit of fiberglass won't help I guess?) but I did replace my heater core and shut off valve about 2 years ago and now I see why I can't get heat to stop coming threw the vents. Due to the fact the whole assembly is not sealed to the fire wall. All in all I think it will still be a little cheaper to replace with aftermarket stock parts.Once I can track down the parts, I just want to spend my money in the right place.
Anyway once the HVAC is done I will have totally purged my car of all the past owner's screw ups..............I hope
Anyway once the HVAC is done I will have totally purged my car of all the past owner's screw ups..............I hope
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Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
I have found a vacuum diagram and it seems that my control head, dosn't work along with all but one of my vacuum solenoids. I am wondering if there is any way to test my evaporator?
You should try pressing the control switch together & try the A/C vac. system.
Pro
Joined: Nov 2007
Posts: 710
Likes: 0
From: Northern Florida
The most likely source of leaks on an old Vettes A/C system, is at the O-rings in each Connector found in the Suction, Liquid, and Hot Gas lines . Other popular places are the compressor shaft seal and the Condensor where a small stone from the road damaged a Tube. Use the Electronic Leak Detector for these areas as well .
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,117
From: Crossville TN
Once you fix the mechanical issues, my advice would be to contact a local Corvette Club to recommend a good A/C repair person. They can test your system, evacuate it, and recharge it in short order. The R12 is rather expensive (compared to the 'new stuff'), but that's easier than replacing half of your existing system. Now, if you find that there are major problems with the system anyway, it's time to convert to the new refrigerant. Have you depressed one of the Schrader valves to see if there is still pressure in the system?
Thread Starter
Instructor
Joined: May 2006
Posts: 144
Likes: 0
From: Stockbridge GA
there is no valves or lines left. The only thing I have that was left under the hood that had anything to do with the a/c system is the dryer and it was covered in 30 years of dirt no telling how long with out hoses. Which reminds me to ask if the dryer needs to be replaced ? or if there is a way to check it
Le Mans Master
Joined: Oct 2000
Posts: 6,362
Likes: 30
From: Oak Harbor WA
If the dryer has been open to the air for any period of time then the dessicant inside is saturated and needs to be either dried out or replaced. I have never serviced one but given the age I would likely just replace it.