CEC Relays

[Andrew P.]

I was wondering if anyone out there could help me in locating a Reversing relay GM 3990842 and a Time Delay Relay GM 3990843. My Delay Relay is working but I figure I'd better get one just in case. I've searched almost everywhere with no luck. Any help would be greatly appreciated.

Thanks,
Andrew (48361)

[Terry M.]

Re: CEC Relays

Keep trying -- these are some of the most difficult C3 electrical parts to find. One year only -- 1971 -- and only Mark IV with AC. They were used on ALL Chevrolet car lines with BB and AC though, so they are not Corvette only.

Joe Lucia will be able to tell us, but I expect they are long GM discontinued, and your only chance will be old originals.

[Kevin G.]

Re: CEC Relays

If your lucky you might find some relay's at your local junk yard. Found a 71 Nova with them still intact and working! The finishes were gone but they work. Also, I've seen them every so offen on Ebay, most times over +100.00

Regards,
Kevin

[Kevin G.]

Re: CEC Relays

I owned a Camaro and an El Camino, both 1971, and both with SMALL block and auto-trans that had these relays.

The Nova I mentioned was also a small block, but perhaps the part numbers were different? Terry?

[Terry M.]

Re: CEC Relays

I thought, based on my reading of the Chassis Service Manual, that those relays were for BB with AC only. It is hard to work through the different applications in the CSM, so maybe I mixed it up -- the manual can't be wrong can it? I am not sure about part number applications --t hat is Joe's turf, and no one does it better.

Just to be sure -- we are talking about the relays that turn on the AC clutch on engine shut down -- or am I on the wrong page?

[Dave S.]

Re: CEC Relays

My 71 LT-1 and 71 ZQ3 w/ AC have 842 and 843 relays.

[Joe L.]

Re: CEC Relays

I thought, based on my reading of the Chassis Service Manual, that those relays were for BB with AC only. It is hard to work through the different applications in the CSM, so maybe I mixed it up -- the manual can't be wrong can it? I am not sure about part number applications --t hat is Joe's turf, and no one does it better.

Just to be sure -- we are talking about the relays that turn on the AC clutch on engine shut down -- or am I on the wrong page?

Terry----


I can't find any A/C application for the 2 relays in question here, although there may have been one.

Anyway, the GM #3990842 relay was discontinued without supercession in August, 1996. The GM #3990843 was discontinued without supercession in May, 1987.

These relays will be found on most 1971 Chevrolets. They'll also be found on most 1971 Buicks, Pontiacs, and Oldsmobiles.

[Terry M.]

Re: CEC Relays

Ah, I was in the wrong pew. Sorry for that mistake on my part.

[Patrick H.]

Re: CEC Relays

These relays show up on ebay on a regular basis. I do not think that they are that hard to find, but then again I started stocking up on them several years ago. The price went from $100 through some vendors about 12 years ago (pre-internet price) down to $20 on eBay relatively quickly once the nationwide market opened up. They tend to be in the $50-80 range recently, though I've stopped following them.

Patrick

[Andrew P.]

Re: CEC Relays

Thanks for all the replies.

I have been looking on ebay for the past few weeks with no luck. I have also contacted NOS retailers and the ones they did have, have already been sold.

All corvette engines in 71 had these relays for the CEC system, which had many functions.

If anyone has any leads, please let me know.

Thanks
Andrew (48361)
1971 350/4spd/AC/PS/PB
45,000 Miles, 2 Owner

[Jack H.]

Re: CEC Relays

Terry, I think you confused the relays for the '71 emission system (reversing and delay; 3990842 and 3990843) for the also '71 only A/C system (anti-diesel and blocking; 3996203 and 3996204). If so, the A/C relays were NOT exclusive to MKIV engines, they were used on all A/C equipped Corvettes. Remember, when we played with my base SB at Joplin until Roy told us to STOP running the engine indoors?

[Terry M.]

Re: CEC Relays

Yep -- that is exactly what I mixed up. Must be those gas fumes from years ago.