Where is the rheostat located?

[slam59]

On my 74 c10 my heater never worked and I never looked into it. But this weekend we were troubleshooting why my headlights would not come on and found out it was my headlight switch had blown and blew out both head lights. Then we saw that the fuse for heater was blown. Put new fuse in and heater came on and all fan speeds worked but would not turn off so we unplugged fan. We did not have time to look further into it and plan on maybe next weekend but friend said that it could be bad rheostat. I looked them up on different sites for pricing but they won't come up. Is this part together with the fan blower or other part and not a stand alone part? Where is it located on the truck?

[ssxty8]

Is this what you're talking about? From RockAuto, 1974 CHEVROLET C10 PICKUP 4.1L 250cid L6 : Heat & Air Conditioning : Blower Motor Control Module / Resistor , STANDARD MOTOR PRODUCTS Part # RU67

[tlawre87]

If you are talking about the resistor its located on the hvac box. The relay is as well.

[slam59]

Originally Posted by ssxty8

Is this what you're talking about? From RockAuto, 1974 CHEVROLET C10 PICKUP 4.1L 250cid L6 : Heat & Air Conditioning : Blower Motor Control Module / Resistor , STANDARD MOTOR PRODUCTS Part # RU67

Yes thats the part. Problem was I was looking it up as the "rheostat' which others call it, but when I looked it up as a blower motor resistor or module, then it came up. But the thing is, the pics on the sites that have it listed, like the pic you posted, they have a different set up for the prongs being that there are 4. As you see the pic I took of mine, it has 3 prongs. Maybe its one of those things where the pic on the site is different from the actual part they stock. You know how they alot of times vary from the actual part they have. I have read that this part can cause the problem I am having when they are going out which is when I set the fan speed to off the fan still stays on low. You can see just how old and rusty the springs are. Most likely original part.

[gmachinz]

No, the rheostat is an ambient temp switch mounted near the evap core that opens contacts if the core temp falls below 34F. It is a NC circuit. If the core gets too cold, it shuts off the AC compressor to prevent it from freezing over.

[f.monroe]

The fuse was probably pulled to stop the fan motor from running all the time. I think that's normal on some of the early 70's trucks. They will run and circulate air even when the switch is off. Most people just unplug the wire going to the fan motor.

[slam59]

Originally Posted by f.monroe

The fuse was probably pulled to stop the fan motor from running all the time. I think that's normal on some of the early 70's trucks. They will run and circulate air even when the switch is off. Most people just unplug the wire going to the fan motor.

The fuse was broken so we put a new one in. And now that you mention it, I think I remember reading a post awhile back about what you mention,being normal for some 70's trucks circulating all the time.


Gmachinz..Oops, i thought this was the part. Thanks for the heads up. will look into the right area.

[gmachinz]

Yeah the climate control cable has an "off" position but the blower fan only goes down to "low" which basically still sends powers through all 3 resistors in series making the blower motor run real slow-so it never really stops.

[ron350]

Slam59 does your blower motor run with the key removed from the ignition switch?

With the ignition switch in the off position the blower motor should NOT be running.

[85chevy86]

The 3 prong maybe for non a/c trucks. When I replaced mine they said with or with out a/c. Might want to check that be for buying.

[slam59]

Originally Posted by ron350

Slam59 does your blower motor run with the key removed from the ignition switch?

With the ignition switch in the off position the blower motor should NOT be running.

No it does not run when key is in off position or removed. My wife's 77 3/4 ton does same thing so I guess it's one of those 70's trucks that stays on huh?

85 Chevy no my truck has no ac so I guess that's why it has the 3 prongs

[Oldriginal86]

On my 77 non A/C truck, I pulled a wire out of the connector to stop the fan from running all the time. I think it was the double wire.

[motornut]

my 78 had a three speed always on fan,I cut the looped brown at the switch.
my 79 had a four speed always on fan,I cut the looped brown at the switch.
the 2 Blower Motor Control Modules are different
in both trucks, now the low is off,both are non-AC trucks