Need advice - Temperature gauge not working

[James1720]

I have a 1990 Ford 1720 with a little over 1700 hours on it.

The temperature gauge does not register, I replaced the thermostat, it still does not register.

I am thinking that the next step would be to recheck the wire on the temperature sender and replace it if the wire is not loose or broken.

Or, could it be the temperature gauge? How often do the gauges fail?

The tractor has an automatic shut off on it; the engine shuts down if the tractor gets to hot. It has done this when the screen in front of the raditor gets plugged while using the rotary mower. Do you think the shut off feature is still working if the gauge does not indicate heat?

 

[automech]

Check fuses/fuse links first. I'm not sure about your exact model tractor but most temp guages can be checked with a test light. Find the sender, it should be a single wire unit on the head or water jacket. Disconnect the wire from the sender and touch your grounded test light to it. The light should glow. If it has voltage available at the sensor then the sensor is probably bad. Voltage comes thru the guage then the variable resistor in the sender grounds it. I don't think the same sensor would work the high temp cutoff. I think a second sensor would be used for that. A check of the wiring diagram would be a good idea if possible. These are general tests though, not tractor specific.

 

[Keoke]

Hi Jim, ground wire at temp sending unit to block with a jumper.
Turn ignition on and watch if gauge starts to climb up to hot.
Don't let temp needle get to max before turning off switch if you want to see the needle again.
If needle does climb to hot with temporary gnd then replace sender. If it does not, then you have possible gauge or circuit problems. However, most common fault here is sending unit.
Note: if gas gauge is working normally look for circuit problems down stream from temp gauge input.
On shut off when hot, if temp sender has more then one wire there is a good chance it is being used to turn engine off when over heating as well. If not then look for another sending unit with a simple gnd or open bi-metallic (not variable as temp sender) set of contacts. Not common, but some of these temp safety switches look for air or block surface temp instead of water temp for input.
Wish you luck on your diagnosis.

cheers,

 

[James1720]

Automech and Keoke, thanks for the direction. I am not very good with diagnostics. I was just going to start replacing parts until it worked again. I will check it out and save a few dollars.

Thanks /forums/images/graemlins/grin.gif