Need help wiring new heater control

[jd21476]

My old heater control on my '73 had a broken lever so I picked up a similar one from a guy on the board here. It looked similar but newer so the electrical connector is different. I need help rewiring it.

[jd21476]

This is my old heater controller

[jd21476]

This is the new.

[jd21476]

This is the old connector

[jd21476]

This is the new connector with new wires that I soldered on.

[jd21476]

Finally here the connector that is still in my truck. The idea is to solder on the new wire extensions and then plug them in to the old connector but it is not working.

I had assumed since the old heater did not have an OFF position and the new one does that I could just leave the bottom one empty and it would work the same as an OFF.

Any help???

[jd21476]

This was my assumption

[jd21476]

Then just plug them in here.

[ray_mcavoy]

The 4 connections on the new switch are +12V FEED, LOW, MED, and HIGH. There isn't a specific terminal for the OFF position ... the switch just doesn't pass power to any of the other 3 connections in the OFF position.

The 3 connections on the old switch were +12V FEED, MED, and HIGH. Notice there's no LOW speed terminal. That's because the wire feeding the LOW speed circuit is joined together with the +12V FEED wire at the plug. Should be 2 brown wires going to 1 terminal. That feeds power to the low speed circuit all the time since there's no OFF position.

So the wires on your existing 3-terminal plug should be:

Brown = one is +12V FEED, the other goes to the LOW speed connector on the blower motor resistor.
Lt. Blue = MED speed connection to blower motor resistor.
Orange = HIGH speed connection to blower motor.


You basically have 2 options to wire up the new switch:

(1) Leave the LOW speed terminal on the new switch disconnected. The 2 brown wires joined together at the plug will cause the motor to run at low speed when the new switch is in either the OFF or LOW positions.

(2) Separate the 2 brown wires at the plug. Identify the +12V feed wire and run that to the +12V terminal on the new switch. Run the other brown wire to the LOW speed terminal on the new switch. That'll give you full functionality of the new switch ... the motor will turn off in the OFF position and you'll still have all 3 speeds.

[jd21476]

So then if I cut off the old connector and wire it to the new wires that I added to the new controller I should be able to have a 12V hot, low, med, and high. right?

[jd21476]

I like option #2

[ray_mcavoy]

Originally Posted by jd21476

So then if I cut off the old connector and wire it to the new wires that I added to the new controller I should be able to have a 12V hot, low, med, and high. right?

You shouldn't have to cut off the old connector. Your original plan of soldering the wires onto the new switch and plugging them into the connector will still work. You were on the right track with what you had tried. I think the only problem was your assumption that one of the connections on the new switch was an "OFF terminal".

Originally Posted by jd21476

I like option #2

That will require cutting one of the 2 brown wires from the old connector. But you can leave all of the other wires as-is.

Unless you trace the two brown wires back into the harness, you have a 50/50 chance of cutting the +12V feed wire vs. the low speed wire. It really doesn't matter though, just cut one of them and then you'll be able to use a test light to identify which one is the +12V feed and which one runs out to the LOW speed resistor terminal. Once you've ID'ed them you can join the one that's still in the connector using your original plug-in plan. And the one that was cut can be joined with a separate connector (soldering it directly to the switch would make future replacemenet (if necessary) more difficult).

[jd21476]

So I got it all wired. The 12+ comes from the back of the instrument cluster and the other 3 that are bundled together are the fan speeds. It was actually fairly easy once you pointed that out to me. I now have 3 speeds and an off.

[ray_mcavoy]

I'm glad to hear that you got it working! And updated to 3 speeds + off