My water thermosensor failed on me a couple of days ago and I searched this forum for ideas. I couldn't come up with much so I'm posting pics of the install. It was easier than people made it seem to be. The biggest part was figuring out which sensor sent the temp reading to the PFC. It was the 1st sensor on the back of the coolant neck. I just had to disconnect a few lines and vac hoses. I found a replacement thermosensor from my local part store, the part was made by Standard Motor Products (Part # TX-40) Here are a few pics......
The location


The old sensor


The new sensor


I hope this will help someone that has a problem with their Thermosensor

 

What symptoms did you have that it was going bad, besides the temp reading in the commander? Also, how much was the parts store sensor?

Good stuff!

Dale

 

I first noticed my car didn't fire up on the first couple of cranks. I had to floor the gas to get it to start, after it finally started it ran like **** belowing smoke out the exhaust. I thought the engine was gone. I got it home and started to poke around. I noticed on the commander that the water temp was -37C before I started it. I turned the key off and then on again and it went to 23C and it fired right up. I guess when the computer thinks the water temp is -37C it dumps alot of gas??? I just replaced my faulty air intake temp sensor like 2 months ago. My car must have gotten a bum set of sensors from the get-go. I paid $37.00 for the sensor which was at cost, I think retail was $60 something.

 

Makes sense - I've worked on FC's that had the thermosensor plug broken off, and they wouldn't hold an idle when cold. Fuel doesn't atomize well when cold, so the ECU richens up the mixture when the water temp is low so the car runs right. If the thermosensor is bad, the ECU will run the car like crap until it's warmed up.

Dale

 

Does any one know if this thermosensor on the back of the waterpump housing with the "green" connector is the same as the fuel temperature sensor?

 

There are two on the back of the water pump housing, the one you can see with the big green plug is the thermostat (8AF5-15-171) and the one below it is one of a few coolant thermo sensors (N391-18-840). That's how I interpreted the parts list anyway. Now I could be wrong, but I believe the thermo sensor on the fuel rail acts as the fuel temp sensor. I didn't see any part or part number for a "Fuel thermo sensor", just coolant sensors.

 

The fuel thermosensor is shorter, same plug though, it may work as water TS but not vice-versa.

 

do the fuel thermosensors ever go bad? what are symptoms?

 

I did the same replacement by just removing the one water hose and a couple of vacume lines. Needed two different wrenches, thought, a box end and and open-end becuase there is only a little room to rotate the wrench. Didn't even loose much coolant making the switch. I think those may be copies of my photographs.

My symptoms were hard starting when cold, but never when warm or hot. After I got the old unit out I measured its resistance vs temperature and compared to the OEM specifications. Found that the old unit was slightly out of spec hot, but way out when cold. My replacement came from AutoZone and at least at that time their listings were backwords for the two sensors. I compared plastic body's color to get the correct unit and its worked fine since. I don't remimber the price now, but they had it in stock.

 

Are you talking about the pictures on this thread that I took with my own shitty camera?