1971 CEC relays

[Robert S.]

I'm in the process of getting all of the components I need for the CEC system on my LT-1. The car has what appears to be the original reverse and delay relays and they probably have not been used in decades. Two questions:

1. Are there basic benchs test I can perform to determine if these relays are functioning correctly? I prefer not to wait until the new wiring harnesses are in place and the engine running.

2. Any recommendations for having these relays restored?

[Alan S.]

Re: 1971 CEC relays

Hi Robert,
There is a description of how the CEC is to function in the CHASSIS SERVICE MANUAL, Section 6T. I don't know if there's enough info for you to be able to test the components. It looks like you need 12v, vacuum and water temperature. Have you thought to look there?
I'm curious about having them restored too.
Perhaps this will help you get some new looks and some more knowledgeable replies.
Regards,
Alan

[Jack H.]

Re: 1971 CEC relays

It's unwise to try and 'bench test' the relays using +12V and ground as you would an ordinary electro-mechanical relay. The Littlefuse version of the reversing relay has an early form of DTL (diode transistor logic) built inside the can. You can 'fry' it trying to exercise it by brute force!

The relays really need to be exercised in-circuit with their respective connecting loads and inputs attached. It's not like there's a MAJOR labor component here to R&R a relay you find to be defective after the car is all together! They simply bolt to the firewall bracket with the engine harness ground wire and the engine harness plug-in connectors affixed...

The article that I wrote on the subject of the 1971 CEC system that was run not too long ago in Restorer Magazine includes the system troubleshooting tables which give step-by-step diagnostics to fault isolate the system...

My take is you're jumping the gun in trying to establish good/bad before the car's put back together!

On 'restoring' the relays, I'd simply clean up the connecting terminals with a wire brush and smooth on a little silicon grease to thwart further oxidation. As far as relay case cosmetics go, it depends on which relays you have.

Littlefuse was the primary supplier and provided BOTH the delay relay as well as the reversing relay. The second source for the delay relay was Fasco and UCC was the alternate source for the reversing relay.

Littlefuse parts are pretty easy to clean up and keep from oxidizing further with a little spritz of clear lacquer so long as you do NOT get paint the connecting terminals or on the back side of the mouting brackets. The mounting bracket backside wants to make a solid electrical contact to the firewall's L-bracket so the two relays enjoy a common ground reference.

If you've got one or both of the alternate supplier relays (Fasco/UCC), the job is a tougher one to restore case cosmetics. That's because each supplier marked these parts with rubber ink-stamp ID's before they shipped to GM.

Just about any attempt to clean/buff or replate the cases of these relays will oblitherate the factory original ink stamps (or what remains of them)...

[Robert S.]

Re: 1971 CEC relays

I have the service manual and the Restorer article on the CEC system, so I'm sure I could work through it if it was all together.

I don't feel I'm jumping the gun. If I'm going through the system, why not check it out now? If there's a problem, I would like to know and look into fixing any problems. Just different view points, I guess. But if not recommended to bench test, I'll not chance it.

If these relays have failed, can they be repaired, or it is best to look for replacements?