heater question and a dumb one

[TxRat]

OK here's deal. This is the first early truck I have owned so I'm still learning.

My truck is a factory A/C truck that has two sets of controls. One is for A/C and the other is for heater.



I have these controls



The middle knob turns the blower motor on by pushing it down correct?

the left knob directs hot air to the defroster by pushing it down?

the right knob directs hot air into the cabin by pushing it down?

My fan doesn't come on but I also can't get the middle knob to move. It appears to be jammed. I just need to understand how it works before I tried to fix it. Has anyone else had the center knob jam up and what can I look at to repair it...

[chevyguys]

The blower motor switch is connected directly to the middle lever. You will probably need to repair the switch or find a replacement.

I had to repair mine (also a factory air truck), they are pretty easy to rebuild. I just (carefully) bent the small tabs back on the switch and popped it apart. I used electrical contact cleaner to clean all of the old dielectric grease out and polished all the contacts with my Dremel. Then used new dielectric grease and reassembled everything. Works flawless.

[TxRat]

OK thanks!!!

[Captainfab]

You could also just replace the switch

[chevyrestoguy]

Once you get the switch cleaned/replaced, make sure you double-check the smoothness of the cable. This may be the reason why the lever will not move. It's not uncommon for them to slightly corrode and bind. A stuck cable is the main reason why you see heater controls with broken levers. The cable levers aren't that strong, and if you're trying to muscle the lever, it'll break.

You can replace the cable, or you can soak it in PB Blaster or Kroil. When everything is operating as it should, the levers should move with very little effort. Make sure you lube what the other end of the cable hooks to as well. Some of the flapper doors can bind up too, a shot of PB to free them up and then a little spray grease to keep 'em lubed makes a big difference.

If you want to study up on the operating functions and switchology of the heater and A/C system, the factory manuals are excellent, especially the Factory Accessory manual. It shows the cable layouts and breaks down the full functionality of each switch.

[64fleetside]

The air/fan cable is really long, and is prolly binding up-it attaches to the bottom of the heater box underhood.

[chevyrestoguy]

Originally Posted by 64fleetside

The air/fan cable is really long, and is prolly binding up-it attaches to the bottom of the heater box underhood.

Good point. I have seen more than a few of those with just a slight kink in the cable that basically renders it completely bound up. Even trying to straighten it with a pair of pliers oftentimes doesn't make a difference. Once the inner wire in the cable gets kinked, you're almost better off to replace it.

My favorite cable is the one on the A/C trucks that controls the flapper on the backside of the heater box. You can only access it from the inside, and even then, it's a bear. You find a lot of the A/C specific heater boxes busted on the top lip that goes over the edge of the upper firewall because guys try to muscle them off because they don't know that there's a cable still connected that they can't see from the engine side of the firewall.

[vpersh]

Just a little clarification: the "Heat" knob really doesn't direct air to the cabin. It regulates the temperature of the air.

[TxRat]

Thanks guys for all the tips/help. I'll dig into it and see whats going on with it..

[TxRat]

OK I got the cable freed up. Fan still wont come on. Looking at the wiring the P/O cut the white wire and put a micro switch and inline fuse in it. Does anyone have a wiring diagram that includes the blower wiring so I can figure out whats going on. I plan on putting A/C in it this summer but until then I'd like to at least get the heater/defroster working...

[rustyrodknocker]

You did run a temporary hot wire from the battery to the motor right? I always do this first only takes a second to make sure the motor runs.
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[TxRat]

Yea, I'll be doing that today, Ran out of day light yesterday. Does anyone know what the white wire is in the heater harness?

[McCoyAZ]

It doesn't get cold in Texas.

[TxRat]

Originally Posted by McCoyAZ

It doesn't get cold in Texas.

HAHA yea your partially right. It doesn't get cold in Texas FOR LONG.

So here's what I found today, This truck is a factory A/C truck but the compressor and condenser are missing but all the under dash and controls are intact.

The fan was toast so I replaced it and found I did not have 12V to the fan repaired the wire going to the fan and now the fan comes on. There is a micro switch on the lip of the bottom of the dash that is wired into the fan control the turns the fan on and off but receives 12V from the factory fan switch? not sure why its wired in this way but I'm leaving it for now as it appears I only have one fan speed this way. I am adding A/C to the truck this summer so all this will be coming out then.

Thanks for the help guys, on to the next problem...

[vpersh]

Here's a wiring diagram that might help:



http://persh.org/images/65Pickup/acwiring.jpg

[TxRat]

Thanks!!!