Ford 3910 temp gauge not working

baker02 · Apr 25, 2017

I've read several of the old posts about these issues but havent found anything thats helped so far. I replaced the sending unit today and checked the connectors. I've also checked the continuity of the wire from it to the gauge and its good. My fuel gauge is working fine so I plugged its wire into the temp gauge and it shot up, so i know the guage is working. The only other thing I've noticed is a wire running to what I assume is the thermostat, Ive no idea what it does though.What am I missing?

trmechapt · Apr 26, 2017

Unplug the wire from the sending unit and ground it. the gauge should move to hot. Make sure the ground wire is hooked up to the gauge at the instrument panel.
Gary

baker02 · Apr 27, 2017

trmechapt said:
Unplug the wire from the sending unit and ground it. the gauge should move to hot. Make sure the ground wire is hooked up to the gauge at the instrument panel.
Gary

I grounded the wire and the gauge shot up. I also checked the wires on the back of the instrument panel and only found 1 ground, all the rest were hot. With that said I'm assuming since the fuel gauge is working, supposedly off of the same ground wire, that there's a break on the inside of the panel leading to the temperature gauge. Would that seem likely to y'all or have I missed something? Also, there is a wire running to what looks like a sensor on the air intake right in front of the engine. What is that for?
I've actually got every thing else fixed except this so I'm doing good so far!

trmechapt · Apr 27, 2017

Sounds like the sending unit is bad if you grounded the wire at the sending unit and the gauge moved. The wires on the intake tube are for the air cleaner restriction light. It should come on when the key is turned on and go out when the oil pressure light goes off. It does that so that you will know the light is working
Gary

baker02 · May 16, 2017

To my knowledge this tractor doesn't have a air cleaner restriction light. I'm wondering if that's the preheater?

I removed the temperature sending unit and tested it with my multimeter and a lighter and found that the new sending unit and the old one are working fine. I know the gauge is working fine because it moves when grounded, I also know the instrument cluster ground should be good since my fuel gauge is working. One of the local shops told me with all that working fine it's probably the voltage stabilizer, which is a small silver box on the back of the cluster. That's honestly the only thing left so I've ordered a whole new instrument cluster which should include the stabilizer. I'll post my results in case someone has a similar issue in the future.

baker02 · May 16, 2017

Also, I found a seller on eBay that offer the full shop manuals, all sections included, for $20 or less. The only catch is that they're on a CD in PDF format, but they're completely indexed and searchable. Seeing as how the actual book runs around $200 I've been very pleased with them. The only thing I'm missing now is a parts manual with an exploded view for identifying things.

JGPenfield · May 18, 2017

You can get a parts manual with exploded view by going to Messicks. They even have an app. You can print the parts diagrams.
I bought a reproduction manual for about $75 and use it all the time. I picked up a second repair manual at Tractor Supply for $40. It is different than the original Ford manual. Sometimes you need a different manual to help you understand what the first one is telling you.

baker02 · May 18, 2017

Thanks JGPenfield! Those diagrams on Messicks are great!

baker02 · May 18, 2017

Replacing the Instrument Cluster on the 3910 did the trick. All the lights and gauges are now working properly. I guess it was the voltage stabilizer...ah well, I know that system front to back now! My local dealer wanted to sell me a new cluster for $200, or a just stabilizer for $110, I found it on eBay for $79 and it looks and works great. Ha.

JGPenfield · May 19, 2017

I am glad you got it working. I try to never buy from the local dealer. Cost is outrageous. Messicks is cheaper but still high because they are New Holland OEM parts. I usually search for the part number on the internet. There are dedicated vintage tractor sites that sell aftermarket parts and EBay has used or remanufactured parts. For example, Messicks wanted >$1000 for a power steering shaft. I found a reconditioned one on EBay for$250.