Survey Help....

[Jack H.]

A GM Licensee asked me for help. He has dwgs for all four variations of 4-speed backup light switches. Their construction, wiring color, wiring length, is quite clear but the sealant used is not.

Specifically, where the lead wires exit the rear of the switch case, a form of RTV was used to seal the switch and provide strain relief to the cables. Some originals exhibit a black colored sealant while others (including service spares) have a light grey sealant.

He wants to make correct parts and is looking for input from NCRS members who ABSOLUTELY-POSITIVELY know their backup light switches are factory originals. The four versions of the switch are:

(1) '63-67 PN 1993666
(2) '68-78 PN 1993430
(3) '79-80E PN 1994218
(4) '80L-81 PN 1994220

Issues he's looking to understand:

(A) Did sealant color vary with PN?

(B) Was there a time line associated with the use of a given sealant color?

(C) Might there have been a distinction based on time of switch mfgr or factory vs. service part channelization?

Replies from club members are appreciated and will help the vendor provide better reproduction parts to all. What's needed is switch number (1-4), color of sealant, and year + approx build date of your car. Thanks.

[Terry M.]

Re: Survey Help....

Jack,

Do you want us to post answers...email you, or (if you give us his email address) contact the vendor? I think I know the answer, but you know about assumptions.

[Jack H.]

Re: Survey Help....

Yes, Terry, I think direct e-mail would save disk storage space on the NCRS website vs. posting individual replies. But, some might be interested in the data.... I can/will share the info (no secrets here) in a summary post at a later date.

[Jack H.]

Three Replies, Thanks! -- Need More....

So far I've gotten three inputs (65, 66 and 70 cars). Two (65 and 70) indicated black sealant and one (the 66) reported grey sealant. Interesting! I could use some more input. I know it's a PITA to crawl under and look, but we don't get too many GM Licensees asking for help, wanting to make parts correctly BEFORE we see them on the judging field!

[Steve Pettit]

Re: Survey Help....

I called the original owner today, he said he had never changed the switches, called my dad who bought 66 in 68, he said he'd never changed it. I've never changed it, so if I can get under car tonight when I get off work I'll send message tomorrow and give you my observations and try to give all other relevant info.

Regards, Steve Pettit

[Chuck S.]

Not Too Surprising...

Jack, you are essentially asking for one-owner, Bowtie original input, and there is not many of those cars represented here. My 70 was gray...I am pretty sure it's original (looked undisturbed, documentation included no receipts or history to demonstrate its change, not a component likely to be repaired), but I wouldn't bet my life on it.

[Terry M.]

Re: Survey Help....

Took me two days and three tries before I got a glimpse of anything other than the exhaust pipe. And I was trying with the digital camera shoved under the car. On top of that the car is on the stock tires, so clearance is as good as it gets.
FWIW: It's gray. 1970 #2161-- body build January 29.

[Chuck S.]

P.S.

I don't know how familiar your friend is with the gray sealant, but mine was actually a translucent tannish gray rather than the typical opaque "battleship" gray you see on caulk down at Home Depot.

Maybe the sealant is actually not silicone at all...the natural color reminded me of some urethane sealant from hell that I used to rebuild a shower once; no known solvent would cut it...acetone or lacquer thinner would only smear it around; xylene was somewhat effective if you rubbed a lot and were patient. I had to throw away the cheap tools, and scrape/abrade it off the others.

I suspect a plain gray would be incorrect, but it's possible the tannish appearance could be yellowing from age. Somehow, I am skeptical that it has yellowed. I replated my switch housing and got as close to the original color as I could. (If you've tried it, you know that trying to colormix silicone don't work for flip. )

Black would definitely be easier, but if you need the "gray", then the black looks like a "cop out".

[Jim T.]

Re: Survey Help....

Jack just checked my original owner 68's known to be original backup light switch. The sealant color is black.

[Harmon C.]

Re: Survey Help....

73,s Gray also 5 cars Lyle