I've got two sensors, left and right, on the back of my 1972 455 from a Riviera. See pictures. What are these for?
Both of 'em? Driving a single dash light? I wouldn't have expected that. I bet one of 'em is for automatic air conditioning--heater fan won't come on if the engine isn't warm enough to provide hot water to the heater core. That sensor probably goes into the water jacket. I suspect the other senses IRON temperature, not coolant, and lights up a dash warning. That's the final warning before the engine melts. I know Cadillac used a sensor that just went into the iron of the head--not the water jacket. That way, if the coolant leaks out (blown rad hose, for example; or a rusted-out core plug) there's still a temp sensor that will work.
Those are blind bolt holes. If you flipped the heads around the holes would be used for accessories. if the head temp gets hot enough to activate that sensor its probably to late.
"Stop Engine" light is intended to come on shortly after the head gasket blows and the head warps. At least that is how it worked for me.
Your assuming that switch is original to the engine. It might not be. Without knowing the complete history of a 50 year old engine, you can't assume that. Interestingly enough, the 72 Chassis Manual talks about a temperature switch mounted on the block to control blower operation. Page 13-111,
I've never heard of one mounted to the BLOCK before. I only see 'em in the head. First Guess: Mistake in the manual. But I've been wrong before.
Agree Larry, however everthing on this greasy slug has looked like factory original. It makes sense that the big cars and Riv had more doodads and automated controls. I'll get out my multimeter and check them out. Thanks Guys!
In my 73, the sensor in the right head was used to turn the blower motor on low speed when the engine reached operating temperature. It was used to pressurize the passenger compartment. I believe it was used to reduce the chance of fumes entering the car. You will notice that on cars with that system, there is no off position on the blower motor switch. The blower motor will run on low when the switch closes. My Grandfather bought my car new and installed a switch on the dash to turn the blower motor off because in the summer, it always blew hot air into the car. Mine is a non ac car.
