Hello

I have some questions to the cooling system of my 1989 Iroc-Z with 305 TPI engine.:

1. How many cooling sensors or switches are on my engine, and where ?
2. Does the Temperature gauge on the instrument cluster use the same sensor as the ECM ? Is the sensor directly wired to the cluster ?

Problem.: My temperature gauge shows to less temperature, but with the ALDL cable the engine temp seems OK ?????

Thanks

 

1: 2.One in drivers side head for gauge, 1 in front of manifold for ECM (black yellow wire)
2: no.

Issue might be the wrong sender in the head

 

I agree with Twin_Turbo, it could be wrong sender in the head. But keep in mind the gauges are not very accurate. How much of a temp difference are you seeing between the gauge and the temp in the datalog?

 

There is also an analog sensor on the underside of the plenum for intake air temperature and a thermal switch on the EGR valve base to indicate when it is open. All of the analog thermal sensors use the same temperature/resistance scale, so any discrepancies are likely due to tolerances of components, wiring, and instruments.

 

If you have oem gauges they are not accurate and get worst with time. Even with brand new aftermarket gauges and proper sensors, the temp between the ECM and gauge varies 5-10 DegF. This is on a 305TPI speed density. ECM CTS takes its reading on front of intake manifold and dash gauge takes its reading on driver's side engine head. I have a back-up Autometer gauge that takes its reading on front of intake manifold and it is in line with ECM CT. I concluded that the difference was just a matter of where the reading is taken.

If you have dual fans, one is controlled by ECM and the other one is controlled by a switch on passenger engine head (stock set up)

Cheers