Is the coolant temp guage circuit isolated from the ECM for engine operations, or is it tied in?

I believe there are two coolant temperature sensors.

 

There's one on the thermostat housing that feeds the ECU, and one on the radiator that feeds the gauge.

 

I think. About 90% sure.

 

But, yes, the engine computer does require a coolant temperature sensor input to control cold temperature enrichment.

 

-=Russ=-

Depends on the model - feedback carbs used a single sender with two spades on it grounded through the manifold. One spade for the dash, and one for the ECU.

 

SPFI/MPFI/Turbo have a seperate sending unit variously located, but usually around the thermostat housing (I know that's where it is on the SPFI).

 

GD

I should have been more precise, it's an 89 gl-10 turbo. I know it has two, one is a sender for the guage in the thermostat housing. The sensor for the ECM is to the rear of the intake manifold, I've replaced both. My guage is intermittent. I think it's just the connection at the connector since I had to replace it but my car seems too run worse when the guage is not working. Maybe it's just a coincidence......

My GL-10 has 2... if that helps.. its MPFI... i just ran out there to check... any reason is a good reason when it comes to opening the hood!

I should have been more precise, it's an 89 gl-10 turbo. I know it has two, one is a sender for the guage in the thermostat housing. The sensor for the ECM is to the rear of the intake manifold, I've replaced both. My guage is intermittent. I think it's just the connection at the connector since I had to replace it but my car seems too run worse when the guage is not working. Maybe it's just a coincidence......

 

87+ digidash has a known problem with Jumpy temp gauges. I have been fairly effective in dealing with this by adding more / better grounds under the hood. It all seems to be ground related.

Oh oH oH OHHH yeah my Gl-10 has the digi, its cool and all.. until the sun hits it and you cant see anything, anyways... my temp gauge always jumps around.. it goes up down.. maybe even side to side it can never make up its damn mind!