[79 Caballero]

Last summer I re-did all the a/c stuff, converted to R134a with the later style r4 "pancake" compressor. Worked fine. Winter got busy, didn't mess with it too much. This summer, no cold air. Added dye and checked with uv light, found the leak, o-ring pinched. I finally changed that today, pulled vacuum, leak check held for 4 hours. Refilled with about 2.5 lbs of r134a while jumping the compressor. Compressor works great while jumping it and pressures read spot on. But when I hook the actual car's electrical connector and start up, the compressor never kicks on. Fuse is good. Anything simple I'm missing?

 

[Caballero Joe]

The low pressure switch on your dryer may be bad $26 at most auto parts stores

 

[Caballero Joe]

BTW, I recommend you order it in person. Ensure the picture looks like the part you need

 

[79 Caballero]

So I'm looking around.....and I don't have a pressure switch, and I have no non-connected connectors hanging anywhere. Where does the switch wire in from?

 

[Hat Trick]

Make sure the black wire on your compressor clutch is grounded properly.
Tom

 

[chris32]

Within this link (post #3) you can see the two wire low pressure switch that is attached to the accumulator.

AC configuration for 1979 with LS swap from Silverado

It's getting hot! Time to get the AC working on my 1979, which has a 5.3 from a 2000 Silverado. It has the original G-body evaporator, plus a low-mount compressor on the 5.3 engine, plus a new 4th gen F-body condenser. I also have the original high pressure line that goes to the evaporator, and...

www.elcaminocentral.com

 

[79 Caballero]

Within this link (post #3) you can see the two wire low pressure switch that is attached to the accumulator.

AC configuration for 1979 with LS swap from Silverado

It's getting hot! Time to get the AC working on my 1979, which has a 5.3 from a 2000 Silverado. It has the original G-body evaporator, plus a low-mount compressor on the 5.3 engine, plus a new 4th gen F-body condenser. I also have the original high pressure line that goes to the evaporator, and...

www.elcaminocentral.com

I see the switch.....I have a port on the receiver drier with nothing on it, so obviously I can put a pressure switch on. However, mine is earlier model and therefore has the thermostatic switch. Can I just remove that and use the same two wires to hook onto a pressure switch?

 

[chris32]

If you follow the power lead from the compressor does it go back to the thermostatic switch? And of so, does the thermostatic switch have power when the A/C and car ignition is turned to on?

 

[Hat Trick]

On my 79 that switch also controls my idle solenoid when the a/c is on.
Tom

 

[VinnyD]

Troubleshooting flow chart from a 1979 service manual

 

[dakazman]

Last summer I re-did all the a/c stuff, converted to R134a with the later style r4 "pancake" compressor. Worked fine. Winter got busy, didn't mess with it too much. This summer, no cold air. Added dye and checked with uv light, found the leak, o-ring pinched. I finally changed that today, pulled vacuum, leak check held for 4 hours. Refilled with about 2.5 lbs of r134a while jumping the compressor. Compressor works great while jumping it and pressures read spot on. But when I hook the actual car's electrical connector and start up, the compressor never kicks on. Fuse is good. Anything simple I'm missing?

My 84 did the same thing, I found the connector spade terminals , not so tight cleaned and re-bent inner connections with the help of dental tools.
You can check for continuity at the switch which should be there if pressure is adequate.
At$8.99 a can of 12 oz, try to work with a shop to pump it down.
dakazman

 

[my87]

This may sound strange, but on my 87, had the same problem. Had my AC redone at a local repair shop, AC was great for 24 hours. next day compressor would not kick in, freon level good. took it back to the shop, every body was perplexed, all the connections were good freon levels correct, What they found was a pressure switch on the power steering unit that shut off the compressor at idle to keep from bogging down the motor when you turn the wheels with ac on. Replaced switch and we're back with ac

 

[79 Caballero]

So mine does not have tge power steering pressure switch. And I changed my ac low pressure switch (actually converted from the old thermostatic switch to a new pressure switch). I didn't think it would be, but what's the chances of it being the controller?

 

[Caballero Joe]

You were able to jumper the connector & engage the clutch, but when you attach the connector to the switch (freon full) the clutch does not engage. So, freon is good & wiring is good. The switch is mechanical just like the wire you used to short the connector.
Wrong switch or bad switch?

 

[Hat Trick]

You were able to jumper the connector & engage the clutch, but when you attach the connector to the switch (freon full) the clutch does not engage. So, freon is good & wiring is good. The switch is mechanical just like the wire you used to short the connector.
Wrong switch or bad switch?

Jumper the switch.
Tom