A little electrical help please

[Edward B.]

Re: A little electrical help please

That's VERY interesting Jeff. I wonder if there was more than one supplier?

Ed

[Joe L.]

Re: A little electrical help please

All------


I'll repeat what I said earlier but with a little refinement. There were only 2 switches used from 1968 to 1973. Now the refinement: Switch GM #3942696 was used for 1968 to 1973. However, for the 1972-73 period, switch GM #3998399 could have been alternately used in PRODUCTION. As I mentioned earlier, the 3942696 was discontinued from SERVICE in 1980 and replaced by the GM #3998399.

For 1974-75 a different switch was used. This was GM #410202.

[Joe L.]

Re: A little electrical help please

Ed,
Here is a photo of the switch from my Oct '68 car. As you can see there is no resistor. On the photo of the switch plugged in you can see an inline fuse. Hope this helps.
Jeff

Jeff------


Assuming it's original to the car and I definitely believe it is, this would have to be a GM #3942696 as the GM #3998399 would not have existed in 1968.

[Edward B.]

Re: A little electrical help please

Well then, maybe I have the wrong switch!!!

I'll have to check my wiring harness this weekend. If there's a resistance wire in there, I've got the wrong switch.

Note that my rear fogger harness HAS been patched in several places, so who knows what's going on.

Ed

[Jeffrey S.]

Re: A little electrical help please

Jeff------


Assuming it's original to the car and I definitely believe it is, this would have to be a GM #3942696 as the GM #3998399 would not have existed in 1968.

Joe,
What is interesting is that the AIM shows the 3942696 with 2 wires and the illustration seems to show a cylindrical piece attached to the switch that may be the ceramic "thing" that shattered on Ed's switch. You are right that this is the original switch.
Jeff

[Joe R.]

Re: A little electrical help please

Joe,
What is interesting is that the AIM shows the 3942696 with 2 wires and the illustration seems to show a cylindrical piece attached to the switch that may be the ceramic "thing" that shattered on Ed's switch. You are right that this is the original switch.
Jeff

Hi Jeff,

I think the ceramic thing would be called an insulator. It's there to keep the resistor from shorting out on the bracket and or switch.

Joe

[Mark E.]

Re: A little electrical help please

After going through this thread, I feel a bit relieved my car doesn't have this option...

[Edward B.]

Re: A little electrical help please

What is interesting is that the AIM shows the 3942696 with 2 wires and the illustration seems to show a cylindrical piece attached to the switch that may be the ceramic "thing" that shattered on Ed's switch.

Jeff, John (Hinckley) taught me LONG ago that you can't always trust the drawings in the AIM, or pictures in factory brochures! The AIM because they didn't always get updated, especially if it didn't effect the installation. The factory brochures because these were always taken with pre-production cars, and between then and actual production, things had a habit of changing. (You can't trust the pictures in the Chassis Service and Chassis Overhaul manuals either because most of the time they just used generic pictures to illustrate the procedure.)

So with regards to the 1969 (and later) AIM, there's a VERY good possibility that the drawing in the 1968 AIM (which is correct for the early 1968 Corvette because we KNOW it used the two wire harness and the same switch with the resistor as in the 1967-1968 Camaro), never got changed in the 1968 AIM (or the 1969 and later AIM's) because it didn't change how the option was installed. I'm going to be pulling my carpet up this weekend and see what I have under there, but again, I wouldn't be surprised to find that my defogger wiring harnesses has been hacked because most of my other harnesses have been! I'll report back and let you know what I find.

After going through this thread, I feel a bit relieved my car doesn't have this option...

Mark, you are EXACTLY right! there are two options that are totally useless on these cars. The C50 Rear Defroster because it does almost nothing, and the U15 Speed Warning because you can't even hear it when you DO go over the limit! Especially in a convertible!

Ed

[Edward B.]

Re: A little electrical help please

Well, I was able to pull the harness assembly out of the car yesterday (what a MAJOR pain), and found it is indeed hacked to bits. It's so cut up it doesn't even work, so time for a new one! $60 plus shipping from Paragon...

Not only that, but the motor retaining bracket is very rusty, as is the backing plate (see attached), so I pulled everything out to do a small restoration. I figure I'll either sandblast the brackets or maybe this will be a good opportunity to try Evapo-Rust.

I tested the motor and it works okay hooked up to 12V, so I don't need to pull it apart. I'll just wire brush the housing and repaint. I'm assuming gloss black.

Ed

[Mark E.]

Re: A little electrical help please

That much corrosion is a symptom of a water leak, so you might check for leaks in the rear compartment while you're under there. The rear window seal and its vent drains are usual suspects.

[Edward B.]

Re: A little electrical help please

Mark, I no longer drive the car in the rain, but the rear convertible top seal was bad when I first got it, so I would imagine that's where the water came from. More than likely from the many baths the car had in its life!

Ed

[Jeffrey S.]

Re: A little electrical help please

Ed,
I am a big fan of Evapo-Rust and this will get rid of all the exposed rust. In this case I would probably opt for sand/bead blasting instead. Any rust that is under the paint will not be removed and eventually will lift any paint you put on. Just a thoughht.
Jeff

[Edward B.]

Re: A little electrical help please

Jeff, so the Evapo-rust doesn't strip any paint that's left on the bracket? If that's the case, then yes, I'll probably just blast it.

Ed