Heater Control Connections Questions

C6c6s

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Aug 9, 2020
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Binghamton NY
Heater and radio went out the other day. Off,on,off,on then off. Checked fuse. P.O had a 15 in there and it was good. Switched to correct 25. Figuring it’s a loose wire. I see this hanging (pic 1) which I’m sure is this (pic2). Colors match. Pull heater half way out and where I’m assuming it plugs in there is one black wire running from the top tan wire terminal. (Pic 3) That feeds to wires of a radio they put in. If they bypassed the original heater switch harness where could it have been pulling power from? And how could it have been working with only one terminal being used? I can only dig in for 15 or 20 minutes at a time during day light because at the moment it’s my DD, it’s freezing here and I can’t take a day off yet to really spend some time. Also, when I was moving it a wire dropped down. I traced it through the firewall under the battery and it feels like it’s going to the blower motor. So where does that connect on the back of the controls? I can’t seem to find a good diagram of that. Tomorrow I may try to unplug that one wire, attach the original 4 point connector and see what happens. I need to find out where the blower wire connects though.

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(edited several times as more things came back to me and I answered my own questions)

There's a micro switch on the right side of the heater control unit that is the true on and off switch, it's activated when you slide the lever to the right. The switch and plug shown are just the speed control. Power come from fuse number...... er I dunno. Bottom right one (?) on my fuse panel (??)

My micro switch had two wires on it (both white? maybe one with a trace? ).

So based on nothing but what I saw on mine, that black wire shouldn't be there, the big plug should. That single wire.. I thought MAYBE is supposed to go to your micro switch? But I don't think so, it's black and has an uninsulated end, so I'm thinking it's a ground, you'd need to wring it out for continuity. (I believe there's a light on the right side of the unit, that black wire could be the ground of your light. Who knows, Im just making wild guesses now. lol)


Recently, I just did away with my heater control unit for a couple reasons. Then not long after, but totally unrelated, it stopped working. I found one terminal in the fuse panel burnt up and blackend. When I tried to clean the terminal up, it snapped off. (swell) Not willing to mess with my fuse panel in the middle of winter (or ever really lol), I just ran a new heavier gauge wire for it from a new sub panel I'd added under the dash.
 
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Yeah, that black wire ties into the after market stereo. Which is why they both stopped at the same time. As time allows I’m going to try to rewire everything up. It WAS working though. I hate trying to get through someone else’s “genius moment” of wiring things up. I have a hard enough time with stock schematics.
 
It actually was working... I think. Only used it once. Was throwing heat (if that’s what you can call it) and no, the large plug wasn’t attached. The black wire from the blower I assume attaches to the micro switch? I’m ‘89.
 
If the large switch wasn't attached, you couldn't have had any control of the fan speeds.

(For all we know the fan speed resistor could be bad and they didn't have any control of the fan speed anyway and figured they had nothing to lose? But why else would you pull it off? )
 
^ that was pretty stupid. If the switch had only one wire going to it, it wasn't doing anything. It can't work as a switch, It can't provide powder, and it's plastic mounted so it can't provide a ground.
 
It’s a mess in there with the wiring. Not just this. Weather permitting I’m going to try to get the radio out of the equation and get the heater back the way it should be. Or at least as close as I can with what they left behind. So many things cut, taped, tied up, hanging....I guess they had it hooked up as a “ on or off” deal. Thinking back, when I turned it on it was full blast. I didn’t even try to adjust speed.
 
Even if you have power hooked to the on/off micro switch, the fan won't run without the large plug attached to the speed control switch. (at least mine won't anyway.)
 
I’m at a loss. I haven’t had a chance to address it yet. I didn’t realize that next day was Christmas Eve plus it’s been really cold here. Up to 27 tomorrow so I may take a shot at it. I do remember 3 other connections hooked to it. 3 in a line. Somewhere on the left side. Maybe behind where the one black wire is hooked up. I didn’t have it pulled out enough to see the micro switch area.
 
In the first picture on this post, what is that part called? I have a 94 Wrangler YJ that connection is 2 separate connections, but I need to replace it. The connection I have now will not stay in place (is old and partly corroded/melted), and the fan shuts off.

I have not been able to find the part or what it’s called as nothing comes back when I search fan speed wiring, heat control wiring, etc.

Any help would be appreciated!

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