Ford 3600 Fuel and Temp Gauges

[fordtractorman]

My fuel gauge reads empty regardless of the fuel level, and the temp gauge goes up to the edge of red and stops ( no evidence of any overheating).
I would appreciate any help to diagnose whether the problem is both sending units or some other problem.

Thanks,

fordtractorman

[praftis]

Did you ever figure out what the issue was?

I have the same issue on my 3930, was that way when I bought it used.

[wjb-49]

Did you ever figure out what the issue was?

I have the same issue on my 3930, was that way when I bought it used.

Have you found the problem? I'm having the same problem with my Ford 340B temp gauge.

From praftis post, this appears to be a common problem.

[shouk]

If you still are having problems, the way the sending units work is based on resistance to ground. Generally as the resistance to ground decreases the gauge reading increases. This makes testing the actual gauge relatively easy. Take the wire off the sending unit on the fuel tank or engine and short it to ground. Make sure you are getting a good connection to ground when you short it and see if the gauge reading goes up. If it does it is more than likely your sending unit. for fuel I usually find that the float has a hole in it and needs fixed or replaced. If the gauges don稚 respond to a short to ground it is usually the connections on the gauges are corroded and need cleaned up, or in the unlikely event the gauge could be bad. Check to make sure the gauges work first. If not check back in and we can go further into the gauge panel. As for the gauges that read up when they should be down (temp in red all the time). Disconnect the wire from the sending unit and it should go to cold. (make sure the wire does not short to ground if your trying to get the gauge to go down)

[praftis]

Can you help me out with how to locate the wire going to the sending unit on the fuel tank? Am I going to need to pull the hood off to get to it?

Are the I&T Shop Manuals any good? Or should I try to find the Ford/New Holland set?

If you still are having problems, the way the sending units work is based on resistance to ground. Generally as the resistance to ground decreases the gauge reading increases. This makes testing the actual gauge relatively easy. Take the wire off the sending unit on the fuel tank or engine and short it to ground. Make sure you are getting a good connection to ground when you short it and see if the gauge reading goes up. If it does it is more than likely your sending unit. for fuel I usually find that the float has a hole in it and needs fixed or replaced. If the gauges don稚 respond to a short to ground it is usually the connections on the gauges are corroded and need cleaned up, or in the unlikely event the gauge could be bad. Check to make sure the gauges work first. If not check back in and we can go further into the gauge panel. As for the gauges that read up when they should be down (temp in red all the time). Disconnect the wire from the sending unit and it should go to cold. (make sure the wire does not short to ground if your trying to get the gauge to go down)

[shouk]

I am not super familiar with the 3930 but if I remember correctly the fuel tank is basically under the cowl. So usually if that is the case the fuel sending unit can be accessed by taking the instrument cluster out. Usually all that requires is a handful of bolts or screws and there is enough slack in everything to pull it out a few inches and look to see the fuel sending unit on top of the tank. Be careful when removing the cluster, don稚 pull too hard or you could disconnect wires and lose track of where they go, not a real big deal but sometimes a pain. Something different between the 3600 and the 3930 (maybe) is that if it has a plastic tank there will be two wires going to the sending unit. One will be just a ground wire and the other will go to the gauge. It wont hurt to short both to ground to check the gauge. Remember to check the ground you are using, direct to the battery with a small length of wire is best, metal parts can corrode and lose their ground. As for the shop manuals, it really depends upon your technical and mechanical abilities. I have a fab and repair shop and get into some things where the oem manuals are helpful. But generally speaking I see a lot of value in the I&T manuals also, and have many of them. For basic stuff they are very complete. Really two different manuals, and for the cost difference go ahead and get an I&T and if it is consistently letting you down get a ford also. They do complement each other well.

[wjb-49]

shouk, Thanks for the excellent explanation of how to trouble shoot the fuel gauge problem. My problem with a 340B is with the temp gauge: it consistently reads on the low side. After the engine runs for 5 - 10 minutes, the indicator disappears. Is the temp gauge tested as the fuel gauge is and where is the sending unit?

Thanks and apologies to fordtractorman for hijacking his thread.

[LD1]

shouk, Thanks for the excellent explanation of how to trouble shoot the fuel gauge problem. My problem with a 340B is with the temp gauge: it consistently reads on the low side. After the engine runs for 5 - 10 minutes, the indicator disappears. Is the temp gauge tested as the fuel gauge is and where is the sending unit?

Testing should be the same way if it is a one wire electrical guage. If someone has replaced it though, it could be a mechanical guage. The universal kind that have a funny looking copper line with like a spring wire wrapped around it. Testing that would be different

Thanks and apologies to fordtractorman for hijacking his thread.

Dont worry too much about that. He seems to be one of the THOUSANDS of "one-and-dones" we always see. His last activity was over a month ago when he posted this and hasnt been back.

Actually, with ~126,000 members here, OVER 86,000 only have 1 post or less

[shouk]

LD1's explanation is spot on, if it is all factory. The gauge should be cold and increase to warm as resistance to ground decreases. That is the standard operation, while it is possible to be vice versa but i have never seen that. As the engine temperature increases the resistance on the sensor decreases. Each sending unit (sensor) has different calibration resistances. This allows the sensor to correspond with correct gauge readings. In my experience when a gauge moves but seems to be off scale somebody has replaced the sending unit with the wrong one. The threads are generally not unique. or the gauge could have been replaced with a gauge that doesn't match the sending unit. If the gauge seems to be correct see if you can find what the correct cold and warm resistances are and you can test it with an ohm meeter. (i don't know what the calibration resistances for your tractor are) if you cant the sending unit is usually pretty cheap can can usually be replaced for less than the hassle of wondering if it is the correct one. But of course first check to see if its the universal kind like LD1 referenced, if not short the wire and see if it goes to hot. If not check back and we will go through some gauge stuff.

[wjb-49]

LD1 and shouk, Thanks to both of you for your help. One question, where is the sending unit for the temp gauge?

Again, thanks!