I have a 1990 Loyale (no turbo). Last week I replaced the timing belts and the water pump. All went well-THEN I flushed the radiator. The temp gauge on the dash stopped working and it appears that the cooling fan is no longer kicking in. Chilton's repair manual [1] identifies a sender with a single electrical lug located just behind the thermostat housing as the "thermometer" and the sender with 2 wire leads (leads built in) mounted in the thermostat housing as the "Water temperature sensor."

 

Why 2 sensors? Which one controls the fan? Which one the guage? And....what does the sensor (2 built in wire leads) installed on the passenger side of the radiator, just above the draincock, do?

 

Perhpas I should have stuck to air cooled VW's

 

Thanks for any help and advice.

 

-stuckagain

 

 

[1] Subaru Coupes/Sedans/Wagons; 1985-96 Repair Manual. Pub #64302. Copyright 1996

the sensor with one terminal is for the gauge itself. the sensor with the green clip is for the ecu

 

the temp switch for the fan is located on the radiator itself, just above the drain valve

This board is great! Thanks Milesfox.

Any idea why both sensors would fail at once (the radiator and the guage)? I didn't touch anything electrical - at least not on purpose. I checked the sensor in the radiator with a multimeter - it seems to be open: I get no reading either in series or from connector to ground.

I would guess that you've got some air in the top of your block that can't get out. Put the front end up on ramps or jack it up and "burp" the system.

Any idea why both sensors would fail at once (the radiator and the guage)? I didn't touch anything electrical - at least not on purpose. I checked the sensor in the radiator with a multimeter - it seems to be open: I get no reading either in series or from connector to ground.

I ASSUME (insert standard joke here) that the radiator uses a make-and-break style temperature switch, as it controls the power to the fan, and it is either on or off. It is unsurprising to me that it is open (depending on radiator temp).

 

I have no clue why thngs failed when you did the flush.

 

Miles, are you pretty certain about which sensor is ECU and which is temp gauge? I am not doubting you , and it fits with me changing one and not getting my expected results. Its just kind of bass-ackwards to the MPFI units' placements (though wire-count makes sense).

I ASSUME (insert standard joke here) that the radiator uses a make-and-break style temperature switch, as it controls the power to the fan, and it is either on or off. It is unsurprising to me that it is open (depending on radiator temp).

 

You are correct, the radiator switch ("thermoswitch" in Chilton), when working correctly, is open until the temperature is high enough to cause it to close. It occurred to me after I posted early this morning. When I got up I marched over to the stove with the switch, a thermometer and my multimeter. I connected the meter to each of the 2 leads and turned on the heat. Sure enough at about 208 degrees F. the switch closed.

I would guess that you've got some air in the top of your block that can't get out. Put the front end up on ramps or jack it up and "burp" the system.

 

Yup! Didn't put it up on ramps, but squeezed the hose coming off the thermostat housing a bunch to get all of the air out. Dash guage works now, RPM drops once engine is warm and fan kicks in when things get too hot. THANKS to all.