testing temp gauge

[JC-jetro]

Paul,

You need to follow Jim's direction and report your findings. Below is the reading on my temp sending unit. Beware that they might not all have the same resistance range but it is more than close for diagnostic purposes. Below is copy of what I said on post#12 of this thread.

good luck
JC,


For the sake of compassion only, The sender on my tractor reports 690 ohm cold, 140 ohms @ T-housing temp of 172 and 92 ohms 1/8" on the right side of the middle @ 196 degrees Fahrenheit.

 

[jinman]

JC, those numbers agree with the ones's in my Repair Manual, so it's probably the same sending sensor. Mine says at 95 degrees F, the resistance should be 670 ohms +/- 85 ohms. At 176 degrees F, the resistance should be 118 ohms +/- 6 ohms. At boiling, the resistance should be around 60 ohms, but unless you take it out and put it into boiling water, you would never see that lowest resistance. If Paul checks his tractor cold, I'd look for the resistance to be around 700 ohms. Without an IR thermometer to know accurate readings when warm, the resistance is just a guesstimate, but certainly the resistance drops very quickly as the tractor warms up.

I copied the parts illustration from Messicks.com and put it below. The yellow circled area and specifically item #44 is the temperature sensor. Maybe this will help Paul locate it. Also, the style of thermostat changed in 1990. Before 1990, the thermostat was as is shown in the green circle (item 45). After 1990, the diagram in the blue circle is the proper one. Since Paul bought his tractor with 200 hours in '93, it could be made prior to 1990 and have the older style thermostat.

 

[JC-jetro]

good info Jim,

I had a few minutes last night and tried to find the same info as you posted from Messick but was not successful as I did not see it under engine or Radiator section. It would been marvelous if they had pics for every item there. Paul should have now everything that he need to sort out his problem.

JC,

 

[twoone]

OK guys- I went back in history to when we purchased the tractor from ford it stated it is a model AL413A 92 production s/n UL32835. So it looks like were dealing with a 92. Now if am lucky and the gauge moves (remember it does not at this time) can't I just assume that the sensor is bad because if the thermostat was stuck open I would still see some sort of rise on the gauge should"t I ??? . I do not have the temp ga youall are talking about and were out in the boon docks and no harbor fright would have to mail order it? what else would it be good for I've never ever had a need for one before please explain some use'es, by the way reason am short handed is that both my boy's are gone one in the navy and the other in the army. Paul

 

[jinman]

Paul, you can't assume the sender is bad because many gages don't budge until your temperature gets up to around 125-130. If your thermostat is stuck open, you would not see the gage move or it would move very little. I know that because I've had a bad thermostat and the gage on my tractor always stayed cool. Are you not able to read the resistance of the sender?

Does your wife have a candy thermometer? You can buy them very cheaply at any Walmart or Target. If you remove your radiator cap and then start your tractor and let it run for a few minutes, you'll be able to put the temperature probe in the radiator and measure the actual water temperature. If it doesn't get up to around 160 to 180, then your thermostat is faulty. Normally your radiator's water temperature won't rise much until the thermostat opens and then you should see it quickly rise on the thermometer.

 

[Travelover]

You can stick a meat thermometer in the radiator with the cap off to get the true temperature of the radiator fluid. .............

................Does your wife have a candy thermometer? You can buy them very cheaply at any Walmart or Target. If you remove your radiator cap and then start your tractor and let it run for a few minutes, you'll be able to put the temperature probe in the radiator and measure the actual water temperature...........

I think this make one complete lap.

 

[JC-jetro]

Paul,

Make sure not to open the radiator cap at operating temperature. water boils at higher temp as internal pressure increases. Water would flash to steam making a dangerous situation of severe burn. If you follow Jim's method then do make sure start the engine with the radiator cap open. when engine is cold the flow is minimal and should increase as engine warms up and t-stat opens up. full flow on cold engine might be indicative of stuck open t-stat.

JC,

 

[jinman]

I think this make one complete lap.

Absolutely! I thought of you when I wrote it.:thumbsup: It's kind of like a circular reference.

 

[twoone]

HI"
Well now that you two have me on the right page and I know what your teaching me and I finely understand what your saying and I know what am doing (i hope) I didn't have much time to mess with the tractor to day had a problem with the well but for a quick check i jumped the sensor wire to gnd. and low and behold the gauge started to move toward hot when I turned the key on now what i have to find out if it is the sender or the thermostat that is bad tomarrow I will see if are meter still works and check the sender any way that's the plan. thanks again, Paul

 

[JC-jetro]

HI"
Well now that you two have me on the right page and I know what your teaching me and I finely understand what your saying and I know what am doing (i hope) I didn't have much time to mess with the tractor to day had a problem with the well but for a quick check i jumped the sensor wire to gnd. and low and behold the gauge started to move toward hot when I turned the key on now what i have to find out if it is the sender or the thermostat that is bad tomarrow I will see if are meter still works and check the sender any way that's the plan. thanks again, Paul

Cool Paul, Slowly but surely we're marching ahead. There is a very good chance that your sender is okay and you just verified your wiring is in connected. T-stats are normally closed valve, meaning at cold condition with engine off it is closed. Most have a small hole to allow some water passage. As the engine quickly warms up during the start up it then slowly opens up. If you have the radiator cap open during the start up and start the engine and notice a lot of flow thru radiator then that might be an indication that your t-stat is stuck open that causes bunch of issues specially for diesel engine. As you know diesel engines do not have spark plugs and diesel fuel ignites by the compression (squeezing ) of fuel being atomized (sprayed in a fine mist) and the warmer the engine the easier the ignition and better operation. Keep us posted and we'll sure help you out.

JC,