A/C & Blower Motor Troubleshooting
 

Hey guys :) I just bought myself a 1981 4 speed about a month ago and I'm trying to fix it up. When I got it the Blower motor would not engage and the A/C did not work, seemingly due to a faulty compressor and a leaky A/C hose. Then, after driving it for a couple days and playing with the A/C blower control switch on the console, the blower, all of a sudden, engaged and worked in every selection, including the different fan speeds, except on A/C. Excited about finally having some cold air blowing in this heat, I swapped out the a/c compressor and clutch with a refurbished one, charged it up and noticed a leak, so I swapped the A/C hose. During this time, the blower motor stopped engaging again! Unless, oddly enough, I would position the blower control switch into "Vent" and push the lever forward (towards the gauges). If I do that, the blower engages and works only on the high fan speed setting. If i stop pushing on it in that direction, it stops working. No other control position works, no matter how i position the switch or lever. This is leading me to believe that the blower control switch and/or the connections to it are faulty, but after looking into it and finding that the control switch costs over 100 bucks I thought I'd chime in here and see what you guys might think/advise. I should also mention that the blower motor resistor seems fine and the relay seems fine. Any help would be awesome, thank you!!

My blower motor had some 'intermittent' functionality as well... When I got the car all fan speeds worked... Then it left me with only high speed... Then the blower motor started making excessive noise... The bearing died... Replaced it... And over a few more weeks I got all fan speeds back again... I'm guessing it's just the connections in the switch that were getting dirty over time... And if it ever stops providing full range of fan speeds again I'll pull it out and try to clean the internal connections...

Replacing the blower motors is cheap and easy... Think I paid $15 at the local parts store, swapped the fan birdcage over, and it bolted up in minutes... Kinda handy that it's on the outside of the firewall and not under the dash ... ;-)

Willcox has a video of how to check out that switch to see if it works. Also saw that switch for about $20

I have to agree with the switch idea, or a connection associated with. If the rheostat fails, the speed in question fails as well, and not intermittently. Like a popped light bulb, never to work again. When I had mine out, I used some spray tuner cleaner in the contacts area. Also, the electrical connections are all male/female spade terminals, and not just on the blower switch. Over time, the females lose their hold to the male, especially if they've ever been taken apart. I take a tiny regular screwdriver and bend the two tabs on the female in a little effectively tightening the connection with the male end. Most of the intermittent issues with our old C3 ladies tend to be with connections. Good luck and post back with your findings!:cheers:

Thanks for the info. I also have a one yes and one day no for the speeds I will pull the motor an clean or better yet while it is out, replace it.

If you take the time to pull the blower out, while it's out would be a great time to improve the airflow with a blower mod as well as remove any leaves or what not in that hole where the blower wheel goes. Mine was full of leaves, twigs, ect.

Thank you all for chiming in. First thing I'll do is try to take that switch out and test all the connections. I'm pretty sure that's the issue. Hopefully that's also the reason why my A/C isn't engaging.

I had a similar issue with my 81. It turned out to be the pigtail connector on the blower relay.

Update: seems like the problem was the a/c & blower motor control switch. took it out, checked all the connections. fan speed switch was fine, but the blower control switch wasn't. fixed it, reinstalled it, and not only did the blower engage, but so did the A/C! really happy about that. the compressor kept cycling on and off because i didn't charge it all the way last time (since it wouldn't turn on) so that was low pressure switch doing its job. After charging it to a suction pressure of 35psi under load, i realized that high pressure liquid line was getting really hot! Does anybody know if this is normal? I couldn't check the head pressure because i didn't have the fitting, but I'm assuming it was high. Thanks!!

Normal-High Side (discharge) Hot
Normal-Low Side (suction) Beer Can Cold....
:thumbs:

Define "under load" when charging

Thanks for the response Patro. I know that the discharge line aka the high pressure vapor line (The one coming out of the compressor and into the condenser) is supposed to be hot, but my question was about the high pressure LIQUID line (the one coming out of the condenser and into the receiver/drier). I've been told that it's supposed to be warm but not hot. Any thoughts?

Thanks!

Oh and by "under load" i meant that the engine was on and revved slightly.