MrLexse

Finally got my 87 started. It runs for awhile and then overheats. The temp gauge on the dash reads zero. I want to get the temp gauge working before I start to troubleshoot the cooling system. I went to the WSM, and it identifies three sensors as temperature sensors (one on the manifold, one on the water bridge and one on the radiator). Which of these three affect the dash gauge?

Landseer

The one shown to the driver's side of the yellow oil fill cap. Wiring diagram will allow you to trace those connections back to the CE panel. You can check continuity and look for cross continuity (short) with the wires disconnected from the sensor. (picture stolen from one of Dwaynes write-ups)


The one to the left side (passenger) and slightly above is the temp II sensor, a different beast and one you didn't mention.


Air plenum sensor and radiator sensor have other uses, mainly I think cooling fan control. Air plenum sensor might be read by engine management system, too. Not sure as I usually work on the 85/86 and its slightly different. P

ammonman

Driver side water bridge sensor=Dash Gage
Pass side " "=Temp II for ignition and injection computers
Radiator sensor=coolant temp for rad. fan control system
Intake sensor = intake manifold temp for fan control system run-on mode for high temps.

Z

On your '87, that temperature sensor on the driver side of the oil fill cap is two devives in one. One terminal of the sensor controls the coolant temperature gauge, and the other terminal of the sensor controls the coolant temperature warning light in that gauge. The sensor body is grounded to the engine.

If the temperature gauge in the car always reads zero, try switcing the wires on the sensor. Another possibility is that the sensor isn't grounded to the engine properly because of something like teflon tape or podwer coatiing on the threads. To check for proper grounding, just connect an ohm meter to the body of the sensor and to the engine block or head.

If none of the above fixes it, check the 14 pin connector by the jump start terminal by the passenger side fender for connection or wiring problems.

Mrmerlin

also note the temp sensor for the warning light and gauge usually has 2 different female slip on connectors,
they are different sizes so the larger one will fit both of the temp sensor male pins but the small female will only fit one.
that is unless some one has replaced one or both of these connectors

Landseer

I think you don't want teflon tape on the threads. Needs to ground to block I think.