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,

 

[jinman]

Cool Paul, Slowly but surely we're marching ahead. It is there is a very good chance your sender is okay and you'd just verifies your wiring is in tact. T-start 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.

"Cool Paul" . . . Is that a pun?

JC, I'm including a photo of my thermostat with the faulty checkvalve/bleedvalve. Paul, these thermostats can fail because the little valve plunger gets out of position and jams the thermostat open. When this happens, the engine never gets hot. The easiest way to solve the problem is to just snip off the little "dangle" and remove it. The tiny hole will slow your heat-up, but not much. It will ensure the thermostat never fails this way again and you can put the thermostat back into your tractor instead of spending money on a new one. If you check your sensor/sender and it is okay, this is probably your problem.

Remember, if you remove the hose adapter neck to get at the thermostat, you are going to lose some coolant. It's best to drain part of your coolant (maybe 6 quarts) into a bucket by using the drain valve on the bottom of the radiator (normally on the bottom right side on the front of the radiator). you don't have to drain all the coolant, just enough so the level is below the thermostat. Before you do that, you will need a gasket, item 48 in the illustration I posted earlier. When you finish, you can put the coolant back into the tractor.

If you end up removing the sending unit, you will also need to drain the fluid the same way so it doesn't leak on the ground.

 

[twoone]

Good morning,
When I was a kid we used to to that what I mean is we would drill a whole in the t-stat to insure that if it would get stuck we would always have some sort of flow for cooling back then they did not have a by pass hole.so I understand. I haven't put a meter to the sensor yet this morning chores first. As for the flow if I open the raid, cap I will brake the vacuum and spill some fluid because of the over flow system, I checked with the war dept. and she does not have a candy thermometer so I guess Ill have to go with the flow (ha ha) am hoping I can find the meter and its working (some time,s the boys had their own places to put things.any way if not we will have to buy them and that will take a day or two before I can get to town or for one to come by internet any I feel thing's are moving, as you said we now know the wiring and gauge are ok. Talk soon take care, Paul

 

[jinman]

You don't need an expensive meter to check the sender, so this one from Radio Shack should work fine. Unfortunately, New Holland thinks their thermostats are made of gold and want over $30 for one. I'm sure you don't want to replace it just to see if that's what is wrong. Also the sender is over $16, so your purchase of a cheap meter from Radio Shack is a good money-saving investment. Heck, you might have a neighbor or co-worker who has one. I have three or four around the house.

 

[twoone]

OK> Called RC they were out of stock so went thru the shop found two meters nether one worked acid and dead battery's spent the morning and part of the early afternoon repairing them was lucky both worked but not sure if there reading correct. went to the tractor outside temp was 95, removed the wire on the temp sender and set the meter and read the sensor to gnd ohm's scale read aprox. 200 ck'ed no matter what scale i went to the other meter it read 184.5 this is with cold eng. opened raid. cap started eng. meters went to 0 after about 12 min. raid got hot to touch no real action except water expanded slightly if my thinking is correct both sensor and t-stat are bad, their was a small pimple going on in the raid when it started and continued with out any change other than the expansion this could have been vibration? but no large flow type action, I have a friend coming over tomorrow and He said I could try his meter so stand by as soon as I test it again i will let you know what happened. Thanks for hanging in. Paul

 

[twoone]

traveler tk's for the idea and looking in I think we have one of those will try tomorrow. keep following.

 

[JC-jetro]

OK> Called RC they were out of stock so went thru the shop found two meters nether one worked acid and dead battery's spent the morning and part of the early afternoon repairing them was lucky both worked but not sure if there reading correct. went to the tractor outside temp was 95, removed the wire on the temp sender and set the meter and read the sensor to gnd ohm's scale read aprox. 200 ck'ed no matter what scale i went to the other meter it read 184.5 this is with cold eng. opened raid. cap started eng. meters went to 0 after about 12 min. raid got hot to touch no real action except water expanded slightly if my thinking is correct both sensor and t-stat are bad, their was a small pimple going on in the raid when it started and continued with out any change other than the expansion this could have been vibration? but no large flow type action, I have a friend coming over tomorrow and He said I could try his meter so stand by as soon as I test it again i will let you know what happened. Thanks for hanging in. Paul

Paul,

Let see if i got it right. You found 2 voltmeters in the shop. You tried to read battery voltage but was not able to do since the meters were bad, right? What did the meter had to do with the battery acid.. you got me a bit confused. Then you said you used same 2 metesr and read resistance in Ohms between the single wire and the ground and both showed around 200 ohms give or take 10. That indicates to me that meter's are reading okay and the 10 ohms difference is not very much and is acceptable. My sender and Jim's shows around 700 ohms cold and at full operating temp and even above it does not go to zero. so I have a strong suspicion your sender is faulty. After 12 minutes does the needle on the dash goes full hot in the read region? if so then again meter is bad as your tractor did not overheat in 12 minutes of operation. If you don't have a large flow in the beginning could be indication that your t-stat is closed like it should be and only getting a bit of flow thru the by-pass hole. we'll see what happens tomorrow. You might call your buddy to see if he had a temp gauge of some sort, even candy thermometer.

we'll see what you can come up tomorrow. some after market sensing unit can also be bought from automotive store. You might call Napa and they might be able and cross reference and get you right one inexpensively.

good luck,
JC,

 

[jinman]

Paul, before you can get an accurate reading on the ohms scale, you have to zero the meter. You do that by putting the leads together and then adjust the ohms zero for exactly zero ohms. If you don't do that, any reading of the resistance will not be accurate. Low ohm resistance is very, very hard to read accurately. Most ohmeters have a 0-1000 ohm scale and may or may not have a 0-100 ohm scale. You have to use the 0-1000 ohm scale for your sensor. If you zeroed your meter, then I apologize for being so detailed, but since you did not mention it, I wanted to bring it up.

It seems to me if your sending unit was just 200 ohms, your temp indicator should have been up in the lower part of the green. 200 ohms would be almost normal temperature, around 140 degrees. That's why I think your meter was not zeroed properly. The problem is that we don't know anything for certain. We don't know the actual temperature, if the gage is working properly (for the correct ohms), or if the sender is accurate. All we know for sure is that if the wire to the gage is grounded, the gage goes to hot. That's a good first step, but not conclusive.

JC, I think when he was talking about acid, he meant the corrosion around his batteries in his meter, not the battery acid in the tractor. Meters that have sat unused for many years with batteries in them are normally a mess due to battery leakage and corrosion. Not sure, but. . . .

 

[Caliche]

"All we know for sure is that if the wire to the gage is grounded, the gage goes to hot. That's a good first step, but not conclusive."

You could always wire in a 1K potentiometer in place of the sending unit and check the meter readings.

 

[twoone]

HERE WE GO: Got up this morning with a new look at life out side temp was a lot cooler and the tractor was in the shade my friend came over with his meter so here's a new report: Using his meter and starting with a cold eng. the sender read around 185 should have read between 6&700 ohm's right? removed raid.cap started eng no action in the raid used wife's meat t-meter to check eng water temp, after running 15 min at 1000 RPM.temp it only showed a little over 120 degree's with no action in the raid. and steady. I think the t-stat's is stuck open and not letting the eng warm up enough to actuate the sensor to show any temp we think maybe his ohm meter might be off as well? but the temp sensor is telling us it's the t-stat??. What do you think? as for the battery's the meter's would not work with bad battery's one is an analog the other a digital. the idea of the meat thermometer came from traveler see another post.

 

[twoone]

HI" thanks for the input, only problem is using a pot. will only tell you if the meter and the wiring to it are ok not the system but a good idea just the same- Paul