instrument cluster

[picanoor]

I am having a problem with the temp and fuel gauge on my tractor. When the engine is off and the battery is disconnected the gauges do not return to cold/empty. All grounds/connections are clean and fuses good. When I disconnect the 2 leads at the fuel sender, with battery connected and ignition on, and touch the leads together the needle goes to full. When just disconnected leads the needle is at 1/4. The gauges are in a container, so I cannot see inside. Any suggestions why the needles are not returning to cold/empty?
When the power is on the temp gauge goes to red hot and the fuel gauge past the full mark.
if i bypass the temp. sender it does the same when i ground the cable.

picanoor

 

[Resqueline]

This type of gages not returning to zero when off is not an indication of a problem. Maybe they have developed some friction but this won't affect their function or accuracy.
So the problem is that they're both pinned when on, regardless of temp & fuel? How about when you disconnect temp & fuel sender, do they go to zero then?
Do you have a multimeter?

 

[Gregm]

Resqueline, can I ask you to reference this post for more detail, it will answer 2 of your questions. I was trying to help picanoor, but found more experience was needed and referenced him to you. Thank you

http://www.tractorbynet.com/forums/john-deere-owning-operating/186544-jd-5310-temp-gauge.html

 

[Resqueline]

Ok, that helps, but my understanding of picanoor's results there are quite vague, and him being absent doesn't exactly help.
Nevertheless it goes like this;
These instruments are of the crossed coil type, with a magnet attached to the needle.
I'll call the coils "ignition" and "sensor" coil. (Since it's a diesel engine I hope that's ok.
When power is off there are no springs or magnetic forces that returns the needle to zero, except perhaps for a weight imbalance of the magnet/needle assembly.
The "ignition" coil always receives power when ignition is on and sets up a magnetic field that on its own makes the needle want to deflect below zero.
The "sensor" coil receives power through the sensor and sets up a field that on its own will make the needle want to deflect past full.
The combined field from these two coils has a resulting direction between these extremes, the direction depending on the balance of the currents through the coils.
The coils both have one end tied to a common positive "ignition" post. The other ends of the coils are tied to each its own post, one for ground, and one for the sensor.
Disconnecting the sensor should bring the needle hard down (below zero). If it's still above full then a short to ground in the sensor wire must be suspected. If the needle only comes to rest (like with power off) then the "ignition" coil is to be suspected.
If the "ignition" coil looses its ground connection then I believe the described fault is the result. If both gages went out at the same time then a common ground (in/to the instrument panel) must be broken.