temp sending unit

[tx_sub]

first off i have a 91 sub 350 tbi. my coolant temp guage never moves. i figure the sensor is bad. i overheated this past summer. must have fried then. which sensor is for the guage? the one on the driver's side head or in the intake manifold near the t-stat housing. is the sensor the same part for both places. i picked up a sensor from advance today. forgot the part number. both sensors look similar. i didn't try to look at the plugs yet. thanks y'all.

 

[4xcrazy]

Drivers side head, the one on the intake is the temp sensor for the computer.

I don't think they are the same either.

 

[tx_sub]

could i get a part number for that sensor. i got the wrong one at the parts store. had the wrong plug. it gonna be fun pullin' that sucker out with the headers and head bolt in the way /forums/images/graemlins/thinking.gif thanks

 

[4xcrazy]

I don't have a part number, but i do know that the sensor that goes in the intake (sensor)runs about $7-$9, not sure about the other one, if you got the wrong the first time, take it back and get the other one.
Should be labeled seperately as "coolant temp sensor" and "coolant temp sender"

"temp sensor" is in the intake, "temp sender" is in the head

 

[pvfjr]

Unless they changed, the sender in the head works by changing its resistance under varying tempperature conditions. It should have a negative temperature coefficient (temp goes up, resistance goes down). The sender should be properly grounded in the head (never use teflon tape), and the guage simply measures the resistance to ground. If you have the ignition "on" and pull the wire off the sender and touch it to a ground, the needle in the gauge should jump all the way up. This will verify that the gauge works. Also, you could check the resistance between ground and the terminal on the sending unit. Don't know exactly what it will be, but if it isn't somewhere between zero and infinity you have a problem. You can also start up the engine while measuring that and see if and how it changes.