Need GM Part and resource for 71 s/b

[Ralph A.]

I am referbushing a 71 automatic with A/C
I would like to change out 3 components that are corroded and can not determine if they are good.
From the assembley manual
1) UPC 12 page A16 the TCS relay indicated on the firewall next to the brake booster.
2) UPC C60 page E9 Under the passenger side dash. GM parts #3996204 and 3996203. The manual calls these relays.

I have tried Dr. Rebuild, Ecklers and Parragon.

Con someone shed some light.
Thanks
Ralph

[Patrick H.]

Re: Need GM Part and resource for 71 s/b

While I have all the components, Jack Humphrey is the expert on these units for 71. I'm sure he will respond.

Patrick

[Joe L.]

Re: Need GM Part and resource for 71 s/b

Ralph-----

1971 Corvettes used 2 different relays on the firewall for the TCS system. One was GM #3990842 which was the reversing relay. The other was GM #3990843 which was the delay relay. Both of these are discontinued and are not reproduced. However, there are still quite a few "around" in NOS condition. These TCS systems were often abandoned by car owners so there was a lot of "parts inventory" of these items left sitting on dealer's parts shelves. These can be found on eBay or through a variety of NOS parts dealers.

The A/C relays are another matter. Both are discontinued and not reproduced, as far as I know. Aftermarket replacements MAY be available; I'm not sure. The GM #3996204 is the easier to find. It was used for some other applications and there are still some "around". The GM #3996203 is much more difficult to locate.

[Ralph A.]

Re: Need GM Part and resource for 71 s/b

I was only aware of the 1 relay on the firewall. Where is the other located?
May need both.
RA

[Joe L.]

Re: Need GM Part and resource for 71 s/b

Ralph------

Yes, I think that you're correct; only 1 of the 2 relays was mounted on the upper left side firewall area. I don't recollect, at the moment, where the other one was located, but there was another one for the 1971-only TCS (or CEC)system.

[Dave S.]

Re: Need GM Part and resource for 71 s/b

Ralph,
The 842 and 843 relays are mounted back to back on the drivers side firewall. I just went through this TCS/CEC system to get my PV on the 71. Its pretty confusing but if you take your time and read the service manual you can understand it. The NCRS operations manual is not specific enough on this subject.

[Ralph A.]

Re: Need GM Part and resource for 71 s/b

Wnet looking tonight when I got home The 2nd relay is mounted under the same bracket. I has a plastic shell wereas the one on the outside of the bracket is tin.
Now I still need the tin one.
Ralph

[Ralph A.]

Thanks Dave - found them

I found the 2 relays. Mine probable work but the one that has a tin case is badly corroded and I am looking for a replacement. The other is plastic and looks OK.
TYhanks fro your response.