Heater Fan runs on and on.....

[VTMopar]

Ok.. got my '70 Challenger, new "resto" -- but the heater fan keeps running, no matter what the switches indicate -- except when you open either door -- then it shuts down.   I should mention that it runs at one speed -- the fan selection switch doesn't seem to make a difference.

I just bought this -- signficant restoration by some folks..... obviously, something isn't quite right.   Everything else seems to turn on and off just fine.

any ideas?   

Thanks
Vermont MOPAR

[Moparal]

 :clueless:I wonder if it's a spring contagious virus or something. I noticed today that on my 70 barracuda ,when I have my radio on and I put the key in the ignition it starts playing even with the ignition off. 43k original miles and everything else works correct.  The only way I know how to fix them is to take the dash out,remove the harness, untape it, and look for a shorted wire.

[6packCuda]

I wonder if the heater circuit and dome light circuit were somehow switched. Does your dome light work?

[Slotts]

I have seen lots of "modifications" to the original wiring harnesses. Almost every time all you can say when you find this sort of modified wiring issue is the 70's weren't kind to those folks. It is very difficult to say what is wrong without some further investigating under the dash.

I would start at your fuse block by removing a fuse one at a time until you could at least identify where the power source is coming from. After that, it's all about tracing the line(s) from there. I would be a good idea to have the wiring schematic to identify a possible miss wire at the terminal block or spade lug connections if nothing looks obviously spliced together.

It's at least a start.

Slotts

[VTMopar]

Its a Vert -- so no dome light.   (However, I did notice that the rear seat lights weren't working (I think they are supposed to be there!) -- this is a brand new experience with this new rig for me!   

Will start with the fuse box -- good idea!   

Vermont MOPAR

[Aussie Challenger]

  Yes my '70 Challenger fan has a mind of its own, comes on when it feels like it no matter whether it is switched on or not. Caused a few problems when driving through the Arirzona desert heat, and now our last Australian summer.      

[Kapteenikosmos]

It's either somehow sorted into some wires related to the door jamb switches or just connected into wrong place. If you need wiring diagrams I can email them to you. I have factory manuals on cd for both 70 and 73.

I'm just putting relays for my heater blower on 73 challenger (my old switch had overheated) and as far as I know the switch only grounds the wires that are coming from the blower motor. I haven't checked very thorougly the diagrams but I suspect that there is a bit heavier gauge wire which supplies constant voltage to the blower motor and from the blower two wires head back to the switch and one of those has a resistor in series for the lower speed function.

Does your car have an AC?

btw, it would make more sense if the blower runs only when doors are open, but it seems it stops when the doors are opened? Only thing that happens when the door is opened is that the door jamb switch grounds some interion lamps.

I will take a look at the wiring diagrams after I get home from work if there is some explanation for the symptoms.

[wally426ci]

I unplugged mine b/c any time the key is on, the fan is on. I found that out at the Drive In Movie's. I could hear it running. 

[VTMopar]

Well, I spent a few minutes over the weekend and discovered that:

1.   The fan switch either doesn't work (somehow I find that unlikely) -- and it basically runs unless either door is open

2.   I removed the fuse for the fan -- still ran

3.   I removed the fuse for the interior lights (no dome, as a vert -- but there is a light under the dash that doesn't come on) -- no change (fan still ran).

They put a new dash (and new wiring) in this car (I just got it) -- so I'm wondering if something isn't cross-wired somewhere......    I'll keep looking --but if anyone has any further ideas -- they are welcome!     

Thanks
Vermont MOPAR

[FJ5_440]

Keep pulling fuses one at a time until it stops, then you will know what circuit is powering the fan.  If they replaced the wiring harness, you might want to get a wiring diagram and trace down the wires back from the fan lead.  It sure sounds as if the ground for the blower motor is coming through the pin switch circuit for the interior lights and not through the blower motor circuit.  I am not absolutely sure they are the same, but the Plymouth diagrams below should give you a start.

I like to highlight the circuit on the digram with the appropriately colored marker, and then follow it through in real life.  I think you will find an orange wire connected into the circuit inappropriately.  Good Luck, these things can take some time, but they are pretty simple circuits.

[Moparal]

You know what I was thinking. The heater plug behind the glove box on a 70 looks close to the horn relay and in the same area, and the door jam switches is in the same harness going to it. I was tempted to hooking up that way by mistake then caught myself. I wonder if the other person did that to you. Just a thought. I bet you will find it soon enough, you got a diagrahm now....

[VTMopar]

Thanks everyone -- The diagrams will definitely be helpful!   I think the "patience" suggestion is the best advice!     

Vermont MOPAR

[Bullitt-]

Should be easy enough to trace the wires from the heater switch to the heater resistor...of course you'll still have to figure out the "courtesy" light circuit, if your car has that time delay relay, no telling what having that wired backward would cause.