A/C Help After 5.3 Swap

[rs67convert]

Hi Everyone,

Recently we finished swapping a 5.3 from a 2002 Tahoe into our 97 Tahoe. It's almost as much fun to drive as our 67 Camaro was. Almost



It would be even more fun to drive if I could figure out why the A/C is not working.

This site probably has more LS swapped vehicles than any of the other sites I get information from, so I am hoping we can figure this out.

I'd like to get the A/C up and working before we take it apart to clean things up a bit.




The compressor is a Sanden 508...




We have a switch on the accumulator/drier. I think this is the low pressure switch...




We have a switch located in the high pressure line between the condenser and compressor. I think this is the high pressure switch.




There are no switches in the compressor itself. Only the wire off of the compressor itself that is supposed to make the compressor kick on when it gets the signal from the computer.



I have found a few different wiring diagrams, but have not had any luck.

This one seems pretty straight forward. I am getting the +12 signal from the HVAC control module. The Compressor Relay in the Underhood Fuse Box is wired correctly, but it's not getting a signal to tell the compressor to go. To get the system filled with freon we bypassed the high and low switch and sent the signal from the HVAC Control Module to the A/C relay.


I guess it's possible that both the high and low pressure switches are bad. Is there a way to check them, or do I just replace them? I'm guessing they aren't that expensive.

Then there is this wiring diagram...



Both wiring diagrams are only using C2-43 and C2-17 on the computer. The second wiring diagram has the low and high pressure switches connected like the first, just at different pins on the connector.


Then there is this wiring diagram. I think it's for a van.


It has things hooked up differently.


So I don't know if any of these wiring diagrams are correct, or if there is a more universal approach to this. I don't know if I have the switches under my hood labelled wrong. I can't help but think this is a pretty simple thing to fix. The A/C shops I have talked to around these parts don't deal with wiring.

[Vimes]

Assuming the dryer was replaced and you vacuumed it down before putting in freon.

You can bypass the pressure switches by unplugging them and putting a jumper into the plugs for testing purposes. See if the system works. You'll want to have a decent set of R134a gauges on while doing this so you can see if the switch is bad or if the switch is working properly because of an under/over pressure situation. When off, both gauges should read the same. This site shows what the readings should be while the compressor is running, with ambient temp being what the outside temp is. It also has troubleshooting tips depending on what the gauges show. If the system is working correctly and the pressures are correct for the ambient, then it's likely the switches are bad. Just plug in one or the other, and if the system doesn't work when it worked correctly with the jumpers, there's your bad switch.

[rs67convert]

Assuming the dryer was replaced and you vacuumed it down before putting in freon.



You can bypass the pressure switches by unplugging them and putting a jumper into the plugs for testing purposes. See if the system works. You'll want to have a decent set of R134a gauges on while doing this so you can see if the switch is bad or if the switch is working properly because of an under/over pressure situation. When off, both gauges should read the same. This site shows what the readings should be while the compressor is running, with ambient temp being what the outside temp is. It also has troubleshooting tips depending on what the gauges show. If the system is working correctly and the pressures are correct for the ambient, then it's likely the switches are bad. Just plug in one or the other, and if the system doesn't work when it worked correctly with the jumpers, there's your bad switch.

Everything was replaced and vacuumed to remove any moisture.

I'm trying to figure out what wire goes where. Of all the things we have had to figure out to make this a smog legal swap for California, I really didn't think that wiring the A/C would be a big deal. Unfortunately I did this to myself while making the wiring harness by not paying attention to the A/C wires. I was just wanting to get the Tahoe up and running. I'll try the different wiring diagrams again and see if I can make anything happen.