Hey guys, I need some advice. I purchased a 1984 corvette a couple of years ago and the A/C didn't work. The A/C switch and the cycle switch that attaches to the A/C compressor was broken off-hence the reason that it didn't work. I renctly replaced both switches and still the compressor does not click on. My question is, does A/C system have to be filled with freon before the compressor will kick-in. Any test I could do to check if my A/C compressor is defective. Thanks I always appreciate the help on this fourm :flag

 

You can jumper the pressure switch on top of the accumilator and if the clutch is working the and compressor isn't frozen it should rotate. (with the engine running)

You may also want to check the fuses to make sure that the fuse is not the problem.

Let me know if this isn't clear and I will try to help more.

Mike.

 

You need freon in the system for it to operate, the freon has to have oil added to it to lube the compressor internals. If you jump it as above just do not run it to long as you can damage the compressor if dry. I'd add 1 can w/oil just to be on the safe side. Can get it at Discount Auto and such. :flag

 

Actually you can engage the AC Compressor clutch with the engine NOT running to keep from damaging anything. Find the wire that goes to the compressor, remove it, and run 12 positive to the lugon the compressor and the clutch should engage with audible click. If it does, then replace the connector, short the pressure switch, turn ignition "on", and turn AC switch on. It should again engage the clutch. The compressor does not like to run without oil/refrigerant and could be damaged by even a short "dry" run. If it engages, have an AC repair shop pull a vacuum on it, check it, then recharge with refrigerant/oil. Good luck.

 

Yea I have checked the fuses, they look fine but I will try your other advice on jumping the switch.
Thanks
DJ

 

A/C is simply a process of having a liquid gas boil at or near freezing so that it can absorb heat. An automotive system and it's circuitry is fairly simple. Generally, ignition power is from the dash control panel out to a low pressure switch (which opens or closes the circuit to keep the boiling point right around freezing and/or to open the circuit if the pressure is too low for efficient operation) out to the compressor, onto the high pressure switch (which will open the circuit just below the point that everything blows up) and finally to ground (sometimes the frame, other times a separate module controlled by the ECM but on the '84, ground is provided by the ECM.

The system needs volume and then pressure to change the state of the gas (provided by the compressor and condensor) so that by the time you want it to absorb heat, it's a low pressure liquid. The compressor needs oil to keep it lubricated and as the gas leaks out you not only lose volume, it takes some of the oil with it.

Most GM's, including the Vette, take 8 ozs of compressor oil and it's really difficult to tell how much is left once the gas has leaked out, but erring on the side of too much is better than too little. If the compressor needs an overhaul or is being replaced, add 4 ozs to the compressor and this sort of repair (or anything that exposes the system to air) requires a new accumulator/drier which should get the balance of the oil fill or another 4 ozs.

Absent a gage set to tell you the exact pressure, you can troubleshoot the circuit (up until '89) by jumpering the low pressure switch which is screwed into the outlet or bigger line of the "boiler" aka evaporator connected to the firewall. If it runs, it's either low on gas or the switch is bad (and 99.9% of the time, it's low on gas). Up until '89, you can also jumper the high pressure switch (located on the high pressure line from the condensor or for an '84, connected to the rear of the compressor), but it's better to use a DVM to see if the contacts are closed. That way, it won't inadvertently blow up and damage your Vette or kill you. '90 and up use a low powered thermistor to tell the ECM the exact pressure and not only will this switch turn it off if the pressure is too high, it will open the circuit if it is too low and store a trouble code that can be read with a scanner. Trying to jumper this switch or reading anything other than voltage can harm the ECM. To troubleshoot the clutch assembly, providing battery voltage and a ground directly to the clutch harness should make it engage.