Water Temperature Sending Unit

[speedmaster]

I searched through the archives, I've looked at the F Engine manual and my Haynes Manual.

I am confused on how it works and how it relates to my cooling.

I've replaced everything on my cooling and after doing some research, I undertand that a faulty WTSU can show high cooling issues. My temp gauge is on the 2/3 mark despite changing the thermostat, water pump, hoses, adjusting the timing.


Well, I found my WTSU what is connected to it? Sounds like a naive question. Does the top connect to some wire that is connected somewhere?

 

[Coolerman]

The top connects to one side of your temp gauge the other side goes to +12V. When the gauge starts warming up it connects itself to ground through the sensor via a variable resistor. This causes the gauge to read. I would get another means of measuring temp to verify your gauge. Maybe one of those infrared temp gauges or even a baking thermometer.

 

[Felix]

That wire goes to your temp gauge. If the sending unit is bad, you'll get an incorrect reading on your temp gauge.

New OEM sending units are pretty cheap. I don't remember exactly, but I'd say 15-20 bucks from cdan.

 

[grant5127]

A simple test one can do is..witha ohm meter...remove wire from sender attach one lead on the meter and ground the other... temp @ 140* resistance should read 90 ohms... 175*/ 50 ohms... to check the gauge... ground sender lead w/ key on.. gauge should peg out to hot.....

 

[speedmaster]

Thanks guys,

My cousin who worked on my car did all the work - carb rebuild, timing, tune-up and change of water pump, thermostat. He says it is fine.

However, I am
wondering how and why my temp gauge is moving if it is not connected to the Sending Unit. When I start the engine, it jumps to 1/2 way mark and within 5 minutes, it goes to the 2/3 mark.

 

[speedmaster]

Here is a picture of it. As you can see, nothing is connected to it.

I am still baffled how my guage could be registering.

 

[nicksfj-40]

I do believe what you have pictured is your accelorator pump on your carb. Water does notrun through the carb.

 

[speedmaster]

no, it is the gold item behind the carb. about 2/6 to the left of the picture in the black.

 

[Poser]

If you do not have anything connected to the sender, then you have something feeding the instrument, causing a false reading.

 

[nicksfj-40]

I see it now. Corrected. 2/6th? Very detailed.

 

[speedmaster]

I think this is a better pict. Its from my crappy camera phone.

 

[nicksfj-40]

I had two in my block. One close to the carb and one farther back towards the firewall. One of mine was unhooked. I put a mechanical gauge in that one.

 

[speedmaster]

Nick,

I have the same set-up. I found the 2nd one close to the firewall and it is hooked up.

What is 2nd one for (the one I have pictured). if it isn't hooked up, whats the point.

I cleaned the ends of the other one and I got better readings. I think I'll replace it.

 

[nicksfj-40]

I dont remember what the second one is for. Maybe emissions?

 

[Ming89FJ62]

The second temp sensor is part of the emissions circuit which also includes a speed sensor (built in to the speedo) and a throttle position sensor (under the gas pedal) plus some BVSV's (bi-metal vacuum swithching valves) on the thermostat housing - and other junk depending on model and date of mfg.