Sending Unit & Temp

[CAPNZ]

The Temp gauge on my 73 BB wasn't working. So I started looking for a used one. On the right side of the engine block it appears to be a sending unit with two green wires going to it. They look good. BUT,while trying to solve my A/C problem I see a shielded wire coming off the altenator that fell off the terminal
just above the spark plug on the left side of the block.

I drove the vette around the block a few times and the gauge seems to be working. Although, I didn't try and red line it at 250. LOL.
My question is: are there 2 sending units on a 454.

TIA
"Jeff"

 

[GaryS]

The Temp gauge on my 73 BB wasn't working. So I started looking for a used one. On the right side of the engine block it appears to be a sending unit with two green wires going to it. They look good. BUT,while trying to solve my A/C problem I see a shielded wire coming off the altenator that fell off the terminal
just above the spark plug on the left side of the block.

I drove the vette around the block a few times and the gauge seems to be working. Although, I didn't try and red line it at 250. LOL.
My question is: are there 2 sending units on a 454.

TIA
"Jeff"

Jeff, the two prong temperature sending unit in the right head is for your TCS, transmission controlled spark, system. Your GM Service Manual has an excellent description of its function and testing. This system consists of a relay (timer), the switch on the trans that only sends a signal when the car is in 4th gear, the temp sender I mentioned, as a solenoid operated unit on the right side of your carb that allows or blocks vacuum advance, depending on temperature, time, and gear position.

The temp sending unit you are looking for is in the left head, somewhere between the 1 and 3 spark plug (I am working from memory on this location). It should have a single connector to it, with a green wire and woven heat shield over it.

Gary

 

[CAPNZ]

Thanks,
The temp guage now works. Loose wire.
Mine is an automatic. There is also a solenoid in front of the distributor that's plugged on one end with a bolt in the tubing and the other end is open. A green and tan wire goes to it. I don't know where these should have been attached.?????
I'll be ordering all the books today.
TIA
"Jeff"