I recently had my check engine light came on and the code told me it was the coolant thermo sensor. I searched thru the Haynes Manual and several online shop manuals and have yet to find an accurate description as to where it may be. I have an idea of where i think it should be but i'm not sure. Can anyone tell me where it is so i can fix this?

1990 Convertible w/ 5spd

 

There is a water temp sensor at the top of the radiator, I have an 89 GTU and I saw it this past weekend. If you have your OEM airbox and conduit still on then the wiring for the sensor runs under the air ducting for the air filter box. Each time I've had a diagnostic code for a temp sensor I've found that its a dirty contact, or a loose connection rather than a bad sending unit. a good cleaning and tight connection usually makes the engine codes disappear after you clear the computer's memory.

 

thankx

 

The water thermo sensor is on the back of the water pump housing. See the free FSM online.

 

^^^what he said

 

yea i was fairly sure that the sensor on top of the rad was the level sensor.

 

Ya it is, because I just replaced mine, all it realy does is control the buzzer that tells you when ur coolant is low.

 

water level sensor = on top of rad
water thermo sensor = back of waterpump housing
water temp sensor = on the block next to oil pressure sender

The only one you really need to run the car is the water thermo sensor because it sends signals to the ECU, the other ones should work of course though and are vital as well.

 

What he said...

gil

 

Just to clarify this a bit, the ECU's thermosensor is on the back of the water pump housing and the temp gauge's sender is on the block next to oil pressure sender.

 

sometimes the sensor is fine, just has been accidentally unplugged or, in my case, the metal connectors on the inside of the main plastic connector (from wiring harness) have been shoved back and no making a connection. if you find that you do in fact need the sensor, i have one (brand new in box from mazda) for sale. i found i didn't need it.

 

You can never satisfy all of them.

 

A little off topic but.... What is the sensor that is on the bottom driver's side of the rad. Its on an s4. Two wires going to it. Thanks

 

its weird.. last night i saw mine popped out... i guess i need a new thermo sensor... i wonder how long i have been driving with t like this...

 

i would think you would have noticed it. the car stumbles real bad when cold, not to mention idle. i have the throttle body mod, but it still can idle cold. when the thermo sensor wasnt connected, it took it a few minutes before it'd idle and starting it was a pain. i finally started giving the safc +30% (more or less, i tried a few) at startup so the car would start. otherwise it took a lot of pedal effort.

again, if you find you definately need one, i have a brand new one for sale.

 

It's a Water Temp Switch. It effects the emissions, in particular the Relief Solenoid and also effects the cold start up where the engine revs to approx 3000rpm on start up. If the water temp is seen as too cold ........it won't rev the engine that high.

 

So if I'm removing all the emissions stuff I don't need it? The reason im asking is because when I pulled my motor it fell apart when i unplugged it and if i don't need to buy a new one i won't.

Once again sorry for getting off topic

 

Correct.

 

Perfect one less part I have to replace.