back window defogger wiring

[k2steve]

Hello,
Can any one help with the wiring harness for the rear window defogger? I installed one in my 70 challenger years ago but never had the two speeds. What I need is the resistor wire for the harness or the value of a resistor needed to wire in-line to the defogger motor or a line on a good harness from the switch to the motor. I have looked all over the suppliers but nobody seems to make a new harness.

[Chryco Psycho]

Welcome to Ebodies from Panama 
Maybe @Slotts can help you out , I would have thought the resister would be in the switch

[Slotts]

Welcome to Ebodies from Panama 
Maybe @Slotts can help you out , I would have thought the resister would be in the switch

Thank you Neil, 
This is Jim reporting live from Pittsburgh...

There are two versions of the rear defogger for an E body. Yes, the one year only 70 version and the 71-74. While the 71-74 did have a resistor coil circuit board, exactly like the ones installed on the E body non a/c heater boxes, mounted into the metal diffuser, the 70 version did not have one.

The way the two speeds were accomplished for 70 only was by using two wires from the kick panel in different size gauge wire. Low was 20g and high was 18 gauge. About two thirds down the harness to the package tray, these two wires were spliced together with a single 16 gauge wire feeding the defogger motor. I do have and can take measurements of the this 70 version if you want them.

The 71-74 used two 18 gauge wires from kick panel to the resistor coil on the defogger motor with a female T connector. The motor plugged onto the output side of the resistor.

And now we send you back to Headquarters in Panama with Neil. This was Jim reporting. 

Just had to try a news story hand off on this post!  

[k2steve]

Thank you Gentlemen,
Jim, that information about how to get the two speeds is great. I just looked at what I have, it is a unit with a resistor. I either wired it up wrong or the resister is bad.  I have two leads from the switch to the motor resistor like on the one on the heater box. The motor has two leads, one black and one green. Green is grounded.
If the resistor is bad, I do not believe I can find a replacement, so Jim, can you measure the harness gauge lengths (3) as you descried?
Thank you for the help to get two speeds on this thing.

[Slotts]

Gee, I guess nobody likes my sense of humor on the first post! It was a long Friday. You're right, just another unemployed comedian... 

Hey Steve,
The first thing I forgot to mention was Welcome Aboard!

Ok, before for trying a rework of the wiring, if you could test your resistor circuit board on the defogger motor would be a good start. In the first picture, I am showing a the 70 version and the 71-74, without and with the resistor circuit board.

The second picture shows measuring the terminal with -5 Ohm impedance resistance for the slow speed. The last picture show measuring the other terminal with 0 Ohm resistance which is the high speed.

If you could test those two points and let us know what you find would be great.

Jim

[anlauto]

Thank you Gentlemen,
Jim, that information about how to get the two speeds is great. I just looked at what I have, it is a unit with a resistor. I either wired it up wrong or the resister is bad.  I have two leads from the switch to the motor resistor like on the one on the heater box. The motor has two leads, one black and one green. Green is grounded.
If the resistor is bad, I do not believe I can find a replacement, so Jim, can you measure the harness gauge lengths (3) as you descried?
Thank you for the help to get two speeds on this thing.

Why is your green wire grounded ?

[Slotts]

Why is your green wire grounded ?

We didn't get that far, yet. One step at a time! Polarity reversed will still make that motor run in the same direction.

Jim

[Chryco Psycho]

Who says we didn't enjoy your humor , I guess I should have responded instead of just reading it & laughing !! 

[HEMICUDA]

Who says we didn't enjoy your humor , I guess I should have responded instead of just reading it & laughing !! 

Yea, you suck, you should learn how to share. 

[CudaMoparRay]

A great  from Riverside, California

[k2steve]

Thank you all for the welcome, I have been lurking on the site finding info as I needed. With this I couldn't find.
I read your replay and tested the resistor, one way 2.5 ohm. The other 0.2 ohm. From resistor to ground 198 ohm.
I was mistaken, the green is the lead with a connector to the resistor and black is grounded.
The readings I got seem to close to the other, I thought it would be a wider spread. I that why it only has one speed?
Thank you for your answers.

Steve
Antioch, Ca

[Slotts]

Oh! All of you are going to like this one for a good laugh and the finger is pointing right at me! 

Hey Steve,
I replied to your post at 5:30 am, EST. I am blaming this on the lack of coffee! I had to have bumped my calibration dial on my meter, posted a picture and gave you an incorrect reading for the slow speed. I am attaching another set of pictures WITH the meter calibrated and there is a difference being shown on the slow speed.

I first said a -5 Ohms amount of resistance on the low speed circuit board when actually it is -10 Ohms. 

So, I just tried using -3 Ohms resistance to see what happens and there is barely a difference in speed. Listening to the motor sounds like the difference between a musical D note and D flat note.

Because of my boneheaded information first given, I would like to offer this. Could you send me an email to jsrestorations@rocketmail.com along with a shipping address. I will send you a working resistor circuit board so you have both speeds.

No strings attached, only a resistor coil to the circuit board. 

Jim

[k2steve]

What an offer Jim, I'll send the e-mail.