I'm wondering if someone (maybe Fred easily could) might be able to take a picture of their rear defrost switch.
I ordered a NOS switch from a Ford Dealership in the mid west, but the part number on the switch doesn't match the one printed on the box. I'm not quite sure if it is the correct switch.
It has two positions, up and down, but has a spring to hold it in the middle. The switch does not stay in either position, it springs back to the middle regardless of which direction I put it in.
The Part number on the box is D2FZ-18578-A, the part number on the switch is D22B-18C621-AA.
Online research says it's a heater control switch.
I don't have access to my rear defroster switch but to be honest it sounds like that is what you got. Mine springs back to the middle no matter what way you work it.
FYI: the switch does NOT apply power to the heated rear window!
From the 1977 EVTM (Electrical and Vacuum Troubleshooting Manual):
"HOW THE CIRCUIT WORKS
"The Heated Rear Window is controlled by a Control Relay and a 3-position Control Switch which is spring loaded to the center position. The system is turned on by momentarily pulling back the switch button and releasing it. This causes the Control Relay to electrically latch itself in the closed position, and the system then stays on until power to the relay is interrupted by either pushing the switch button forward or switching off the ignition. An Indicator Light shows when the Heated Rear Window is on."
The manual shows that the "Heated Rear Window Control Relay" is located "Behind the instrument panel above the glove box."
As it happens, I plan on pulling one this weekend (assuming it isn't torrentially raining). If I get it, I'll photo the relay and ancillary wiring harness(es), etc.
Good luck!
Mike
78 picture.
Dave, switch removed. 2 each mount screws. Fred :)
Fred: what's the relay look like (and where was it located)?? :D
Mike
Mike, if I remember correctly, the relay is silver (metal housing) approximately 2"x2" x.5" thick. It is located above the glovebox probably closer to the radio. I think I have one loose somewhere, I will see if I can find it and post a picture.
Here is relay loose in 1 and mounted in another around ash tray area bolted under dash. Has heavy gauge wire going down right side to rear of car. Fred :)
In the 3rd picture you can see speaker grill to the left so that will give you idea on location.
Thanks Jerry! Thanks Fred! Clickin' on the positive for you guys this morning!
Mike
Thank you Fred and Mike, I appreciate the pictures and help about how it is wired up.
Fred, you've got a message!
This is your ground wire to left side of window. Looking through outer tail light bulb access [cover removed]. Fred :)
Interesting! The one I just pulled off of a '79 wagon was just a short guy that terminated at the center bolt of the hinge on the tailgate. Pictures soon (I promise).
Mike
I know on my 78 I had back in 2004 I had the rear defrost but don't think it ever worked. When the car got junked I took the wiring & switch so I could install it in my 77. That was almost 6 years ago & it has yet to be done lol.
Mike, the rear defrost glass I have, I pulled off of a 78 station wagon and it had a ground like what you describe, terminating at the lift gate hinge. I plan to use that section of the wiring, but I am getting the complete circuit from Fred, so hopefully everything still works out once it's all hooked up!
Excellent! Just remember, without pictures, it didn't happen! :coolafro:
Mike