CEC Temp sensor "What is Hot"

[Michael G.]

Does anyone know what the temperature would be for the sensor (right cyl. head) to send a signal for the hot side of the sensor. 71' 350/270. I cant find the stats in any of my manuals. Thanks, Mike

[Terry M.]

Re: CEC Temp sensor "What is Hot"

I thought we put that in the TIM&JG, but it might be in the 1968-1972 Operations and PV Manual, or it might be in both of them. I can't remember.

[Kenneth T.]

Re: CEC Temp sensor "What is Hot"

Below is a snip of section 6T of the 71 service manual.

"A thermostatic water temperature switch is used to provide thermal override below 82 F. The time delay is incorporated in the circuit to energize the C.E.C. Solenoid Valve for approx 15 seconds after the ignition key is turned on. Full vacuum to the distributor independent of engine temp for this time interval improves drive away and eliminates stall after start problems. This relay covers engine temperature conditions above 82F.

I don't know if that's what you are looking for, but hope it helps.

Ken

[Jack H.]

Re: CEC Temp sensor "What is Hot"

The spec he's looking for isn't quoted in the Chassis Service Manual. It's an 'exception' condition (car in grid lock, bumper to bumper traffic and about to overheat) that triggers the RH cylinder head's thermal switch to close and re-engage the CEC (boost idle RPM and provide vac to the distributor).

The spec IS quoted in the 1971 Chevrolet Emission Control Systems phamphlet as well as the 1971 Combined Emissions Control System Training System Booklet. The hot side threshold of the switch is set to trip at 232F.

I've actually watched my system cycle ON/OFF/ON/OFF while participating in a 4th of July parade! I'm happy to report it worked like a charm and the cooling system did NOT blow the rad cap while other, older, Corvettes in that parade weren't so lucky...

But, that's not a feature/function we test/verify at NCRS! It would require blocking air flow through the radiator with a TREMENDOUS potential to 'backfire' on the judges + the owner...

[Kenneth T.]

Re: CEC Temp sensor "What is Hot"

I remember back in the day as they say. We were on a vacation trip and stopped for ice cream and when I restarted the car the rpm went up and the thermal fan kicked in, sounding like a wind storm. My wife looked at me like what is happening? You are the man on CEC, I should have waited for you to reply.

[Michael G.]

Re: CEC Temp sensor "What is Hot"

Yes Jack, You are the man when it comes to CEC. All I have learned about the system has come from you or your articles. I would love to get my hands on a copy of that suplimental pamphlet one day. Thanks, Mike.

[Terry M.]

Re: CEC Temp sensor "What is Hot"

Watch on fela-bay or at the swap meets. I see them once in a while.

[James B.]

Re: CEC Temp sensor "What is Hot"

Yes Jack, You are the man when it comes to CEC. All I have learned about the system has come from you or your articles. I would love to get my hands on a copy of that suplimental pamphlet one day. Thanks, Mike.

Michael:

Here is a scan from the TCS section of my '72 Chevrolet Emissions Control Booklet to give you an idea of the kind of information that's in it.

James

[Jack H.]

Re: CEC Temp sensor "What is Hot"

PS, the 'infamous' '71-only CEC system continued in production for 1972 with the on-hand inventory of parts being used up on 6-Cyl Chevy passenger cars. So, sometimes you'll see this/that '71 CEC component advertized as being '71-72 applicable... This is essentially true, but the V8 emissions components are NOT the same for '72 as they were for '71...

[Michael G.]

Re: CEC Temp sensor "What is Hot"

James-Thanks for the attachment. Interesting stuff. Jack-Thanks for the clarification. In all I have read, this 71' CEC was a "one year wonder". I think I have the system fully operational but can't get the 232 degrees I would need to check the high end. I need to finish the AC system and have it sit with AC on and see if I can achieve this high temp. Thanks Guys. Mike