Go BottomFuel Guage Problem
 | bmark
Join Date: Posts: 1 
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2001-07-13 30050
I just acquired a New Holland model 1925 (used) and the fuel guage does not work. I don't have a trailer to take to tractor to a dealer for service, and was wondering if this is a common problem or if there is an easy way to fix or diagnose the problem. I've already checked the fuses and connected the electric leads to the tank, the guage rises to about 1/4 tank. I'm considering just purchasing the in-tank module to see if that's the problem. Any help anyone can provide would be appreciated.
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 | harvey
Join Date: Sep 2000 Posts: 1550 Moravia, NY 
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2001-07-14 30060
Look down in the tank and you should be able to see your float. If you need a light... use a flash light and turn it on away from the tank and any fumes. Use some baler wire to reach in and raise the float and see if it registers full that will narrow down your fix. Most likley float is sticking on something in tank and the rod can be bent to one side to clear it. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2001-07-14 30065
Harvey's suggestion seems like a pretty good idea. I am finding that the electricals on my mid-80's 1710 were getting a bit shaky. My temp gauge quit, which I got going by jiggling and cleaning terminals. The gauge lights quit which I got going by cleaning fuse holder contacts. My lights quit, which also proved to be dirt on the fuse holder. I think a new maintenance routine 'cleaning the electricals' should be defined at 10-year intervals. If Harvey's suggestion doesn't work, I would make sure the sender unit is getting voltage before buying a new unit. ....
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| Stan in Calif
Join Date: Feb 2002 Posts: 47 Sacramento Valley- Glenn County
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2001-07-15 30096
You can do this by removing the wire from the sender, and with the ignition on,hold this wire to a good ground on the machine. The guage shold rise to the full mark, indicating that the guage and wiring are ok. If it doesn't, try again - you are probably not getting a good ground. The reason I say this is because guages are very reliable. The problem is almost always with the sender - usually the float. They can become saturated with fuel over time and sink, giving a low or no reading. You should be able to get a float and new gasket at your local auto parts store. With this and Harvey's and Tom's suggestions, I think we have it. If not, come on back. ....
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| bmark
Join Date: Posts: 1
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2001-07-18 30204
Thanks for all the help and suggestions. Here are the results:
I could never see nor reach the float in the tank so I was not able to actuate the float with it still installed in the tank. I did remove the float assembly and tested the float in a container of diesel. It's bouyancy appeared to be adequate.
I grounded the lead with the ignition on and the guage rose a small fraction (maybe 1/16 full) so in my mind, this test was not conclusive. I then attached a nine volt radio battery to the leads and the guage rose to about 2/3 full.
At this point, I'm thinking the problem is the sender. Any additionl thoughts?
Thanks, Mark ....
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| BillBass
Join Date: Feb 2002 Posts: 190 North Texas
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2001-07-18 30218
9 volts giving 2/3 gauge would imply 12 volts would give full gauge, so I think you are correct in assuming a bad sender assuming you have verified that all the wiring to/from the sender and gauge are good. I believe most sending units are basically a slide wire resistor. As the float moves, it slides a wiper up and down a resistor providing a variable voltage to the gauge. Most likely the sliding arm of the resistor is either broken, stuck, or dirty. You can determine this with an ohm meter across the connections of the sending unit while moving the float arm. You should see a range from near zero ohms to some max. reading depending on what the total resistance is. ....
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| Stan in Calif
Join Date: Feb 2002 Posts: 47 Sacramento Valley- Glenn County
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2001-07-18 30220
There is something funny going on here - you are getting a higher reading (1/4 full) through the sender than you are going straight to ground. These things work by the sender completing the circuit to ground -you should get a higher reading going straight to ground than through the sender. Does your guage read full with the ignition off? If so, proceed to resistor check as outlined by Bill - gauge is ok. If not uh-well, check the resister out anyway- it's probably the second most likely culprit. If you don't have an ohmmeter, hook the wire back up to the sender, ground the base of the sender with a jumper wire and move the float arm through it's travel. This should show you how the sender is behaving. If it goes to full - looks like we're back to the float or bad ground on sender or tank. ....
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| bmark
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2001-07-26 30393
I tried all the suggestions and was never able to fully diagnose the problem. There appears to be some confusion about the results so here is is again. I grounded the sender wire and the guage moved up to about 1/8 tank. When I attached a 9 volt radio battery, the guage moved up to about 2/3 full. So it seems like the guage is working although I'm confused as to why the guage would not read full when I grounded the sender terminals. I'm wondering if I may have a wiring problem. Anyway, I checked with my local dealer and decided to invest the $31.00 for a new sender. If this doesn't work, I'll start investigating the wiring. ....
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| Dogman
Join Date: Posts: 1
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2001-07-26 30395
bmark
Ifo ground the sending unit, the guage should read full.make sure you have a good ground though.If the guage doesn't read full ...the guage is bad....
dogman ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2001-07-27 30436
I don't know where in the circuit the gauge was grounded. My sending unit has two leads going into the tank. I guess the ground lead is brought out of the tank and attached to a ground bus. Jumping the hot lead into the tank should ground the gauge, but grounding the other lead would leave the sending unit in the circuit. If I were using the leads into the tank as a location to ground the gauge, I'd pull apart the connectors to both leads and test with a VOM. The hot lead should show close to battery voltage, which also would be a test for some possible wiring problems. ....
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| BillBass
Join Date: Feb 2002 Posts: 190 North Texas
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2001-07-27 30450
I looked at the schematic for my JD 950. To the fuel gauge, it shows two hot wires (from two different fuses), one ground wire, and one wire from the sending unit. I have not had to do any trouble shooting on it, so I am not sure why it has two hots. Apparently there is some circuit inside the gauge that requires it. If you have a schematic of your tractor and a volt/ohm meter (VOM), you should be able to isolate the problem fairly quickly by checking the voltage at each termination point.
Can you remove the sending unit from the tank and leave the wiring connected? If so, you should be able to move the float up and down and see the gauge move. If you have a VOM, you should also see the voltage change on the wire from the sending unit to the meter. ....
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| Stan in Calif
Join Date: Feb 2002 Posts: 47 Sacramento Valley- Glenn County
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2001-07-29 30490
Bill-
I suspect that second hot wire has something to do with the voltage limiter that is typically used to provide voltage at a constant level for accurate gauge readings. These are usually attached to the fuel gauge and feed the other gauges. My experience is mainly with american made cars and trucks, so I may be off base, but that would be my guess. ....
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| keoke
Join Date: Posts: 1
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2001-07-31 30533
Hi guys, this may or may not help. There are two basic types of automotive fuel gauges. The most common type is the the "bi-metallic hinge type" this one works as describe by Stan and others. With one acception, it usually does not run on 12 volts. It instead uses a voltage regulator to knock 12 volts down to about 6 to 7 volts. Running a gauge on varying charging voltage would cause it to read hi or low as charging voltage changes. So, a base line voltage must be used instead. The other type of gauge is called the "balancing coil gauge". This type is favored by GM and the English car people. This gauge runs on 12 volts and works the opposite of the bi-metal type when grounding the sender wire at the tank. The gauge will go to empty instead of full. Most industrial and farm equipment will use this type of gauge. Quickest way to tell the difference between the two gauges is when you turn on the ignition. If gauge rises slowly it is the bi-metal type. It takes time to heat the bi-metal hinge and move the needle. If gauge jumps up, or starts at it's last level mark, it is the balance coil (electro-magnets) type.
The reason some of these balance-coil gauges do not return to empty when off (GM) is a damper placed on the needle to keep it from jumping around as the fuel slushes around in the tank.
take care,
keoke
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| bmark
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2001-08-07 30759
Thanks Keoke, that makes a lot of sense given the results of my limited tesing. I did finally receive a new sending unit from my dealer and I installed it this evening. Unfortunately, the guage still will not work. I'm now at a loss since I don't know how to further diagnose this problem. In any event, thanks for all the good suggestions.
Mark ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2001-08-08 30779
An idea that just popped into my mind is that mystery electrical problems often result due to loss of, or bad, grounds. If a wiring schematic is available, I'd try to determine ground paths for the various components and then use an Ohm meter to see if any grounds are open or resistive. ....
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| Stan in Calif
Join Date: Feb 2002 Posts: 47 Sacramento Valley- Glenn County
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2001-08-08 30789
Here's a good one, Tom, to illustrate your point. One time I hooked up a boat trailer that had separate stop/turn and tail lights. I turned on the tail lights and hazard flashers, and much to my surprise, the turn signals on the trailer didn't work, and the tail lights flashed. I knew that it was wired correctly, because it worked before. I finally determined that a bad ground between the tow vehicle and the trailer was passing just enough current to illuminate the tail lights, but not enough for the larger filaments in the turn signals. When the turn signals "came on", they drew the current away from the tail lights, causing them to go out. I don't remember what finally clued me, probably the fact that the tail lights on the trailer were flashing alternately from the turn signals on the truck. Ever since then, when there's something weird going on, I run a jumper wire back to a known ground.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2001-08-09 30806
Stan: That must have been a head scratcher all right. This discussion does remind me that the horn on my 1/2 ton is sounding pretty sick again. I replaced the horn 3-4 years ago, but the ground was the problem. I fixed the ground but guess I did a crappy job. I had a sideline live sound & lighting company for about ten years. Grounding problems associated with moderate sized music PA systems can get unbelievably complex. Every time you go to a concert and hear a PA hum, it's a sign that grounding problem weren't solved. The trouble with faulty grounds is that there are voltage drops across them. You get voltages, or wrong voltages, in all sorts of unexpected places. ....
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