electrically troubleshooting A/C/heater switch

[gramps77]

Has anyone got a method to troubleshoot from the A/C and heater panel to verify where a problem lies?
I can shoot wires just fine if I have a step by step (IE, in this switch position you should see X volts)
The problem Im having is a replaced my HVAC panel with one from LMC and it appears the switch is junk. Reason it was replaced was the faceplate was cracked and the lettering was wrinkled and in bad shape and the switch before I thought was bad but it looks like it was the relay.
The new LMC one use to work in only the lower 3 settings and now if I manipulate it can get it to work in only high, the lower 3 no longer work. The thermostat assembly that goes in the box on the engine side gives the same result at the slider switch regardless if I use a new one or the original, so I assume its the switch. I WAS going to replace the whole system with Vintage Air but looks like I can save some bucks. Thank you

[tucsonjwt]

In my case, the connector/harness at the back of the control was worn out, and not making a good connection. So, I could sometimes wiggle the fan switch and get the control to work. I wrapped electrical tape tightly around the connector and that worked for a while, until the heat relaxed the tape.

I live in the desert and have found that after 30+ years the heat dries out all rubber and plastic parts and I have had bad connections all over the truck. You can still get that harness by checking the online OEM vendors for the Delco pigtail/connector catalog. Post back if you need a harness and cannot find one. Discount OEM vendors have the best prices and part availability.

[gramps77]

which harness were you speaking of? would you have a link? I wanted to rewire the whole truck like I did my 65 Nova, but am finding that for whatever reason, full factory harnesses arent available like they were for the car

[tucsonjwt]

I used Delco PT1936 in my 83 C20. I got it from OE Warehouse with free shipping over $25. Here is a link to Dave's Discount Auto Parts which has a fitment feature so you can check if it is the correct harness for your truck:

http://www.davesdiscountautoparts.co...1977&model=c10

I always check the usual suspects for parts and always try to get GM OEM or Delco on electrical parts. Also, I always search google, Amazon, and Ebay to see if somebody has an OEM or Delco part cheaper - but be mindful of shipping cost. Here are the "regulars" I check:

www.oewarehouse.com
www.oehq.com
www.autopartstomorrow.com
www.gmpartsdirect.com
www.rockauto.com

I know of no way to check if your connector is bad, other than wiggle it around while operating the A/C controls like I did. The problem for me was that the connector would not hold tight enough to make consistently good contact when I reinstalled the A/C control in the dash - the harness would push back on the connector and loosen it once installed.

[gramps77]

Originally Posted by tucsonjwt

I know of no way to check if your connector is bad, other than wiggle it around while operating the A/C controls like I did. The problem for me was that the connector would not hold tight enough to make consistently good contact when I reinstalled the A/C control in the dash - the harness would push back on the connector and loosen it once installed.

Thats a similar issue Im having. So it wasnt the switch itself? I can wiggle it and get it to work in high but if I hit a good bump in the road, it kicks back off. I assumed just the switch, but wanted to make sure voltage was good going to it

[tucsonjwt]

My switch was fine, my HVAC control was fine - my problem was the connector.
Operate the HVAC with the control out of the dash, wiggle the connector, if it works when wiggled I would buy a new connector/harness.