L2550 - Gauges don't work

[Stinger23]

None of the gauges on my tractor work (tach, hour meter, fuel, temp), however, the idiot lights all work. It appears they've not worked for years as the hour meter shows 1006 hours but I suspect it's much more than that based on paint wear and such.

Is this a common issue that might have an easy solution (like a single wire that's shared between all of the gauges that could be fixed and all of them start working) or is this a much more difficult issue to resolve?

These parts are either not available or crazy expensive so I'm hoping the actual gauges aren't faulty. If they are, I'll be looking into building a new panel with "universal" gauges if I can figure out how to get it all working.

Thanks for your input.

 

[North Idaho Wolfman]

You have an overwhelming theme going on with electrical problems.
Get a good test light and use the WSM to find out what is and is not getting power.
The hour / Tach is mechanically driven so it's not an electrical issue.

 

[Flintknapper]

Sounds like some time spent visually inspecting all the wiring on that tractor might be in order. It is not uncommon to find places where rodents have chewed on/through wiring.

On a tractor that age (and assumed condition) I would expect to just replace certain less expensive items rather than spend hours of diagnosis (while still NOT just throw parts at it). New ignition switch comes to mind.

Best of luck. Electrical gremlins are no fun to run down usually.

 

[GreensvilleJay]

Guess I enjoy 'oddball' humour ! With a good wiring diagram and DMM, that tractor is a 'fun' electrical project. '90s era machine (?) so NO computer ?? Just a battery, switches, wires and EM gauges.
1st step ..get the wiring diagram, which will also have colour code.

since none work (gauges ) I suspect bad +12 to them(blown fuse, no fuse, corroded connections, vermin chews...... but need to see wiring diagram .

 

[Stinger23]

Thanks guys, I'll remove all of the covers around the gauges so I can get to the wiring. Hopefully it's something simple. The tach being mechanical is good info. Probably a broken or disconnected cable in that case.

 

[Flintknapper]

Thanks guys, I'll remove all of the covers around the gauges so I can get to the wiring. Hopefully it's something simple. The tach being mechanical is good info. Probably a broken or disconnected cable in that case.

^^^^^

Almost certainly the problem.

 

[Stinger23]

I didn't find any good news while trying to diagnose this issue. I started by checking all of the fuses and found one that was burned up but it didn't appear to fix anything when I replaced it.

The tachometer drive cable appears to be perfectly functional as it turned when I cranked the engine over after it was disconnected from the back of the tach. As far as I can tell, the part where the tach drive cable connects to the back of the tach is broken. I can't find any pictures of what it's supposed to look like, but best I can tell the part that it threads onto is not supposed to come off of the back of the tach.

All of the wires for the instrument panel go into a round connector that is bonded to the circuit board. The power pin has 12v and the ground pin is a good ground. All other pins on that connector are dead though and I could not do anything to make the gauges move. I tried grounding the gauge pin and they did not react. I tried applying power to the gauge pens and they did not react either. I checked the ground at the fuel sender and it is grounded. However, the yellow wire at the fuel sender appears to be dead as it has no voltage. I tried applying voltage to it from the battery but the fuel gauge did not react.

I'm not sure I'll be able to find a new tach for a reasonable price. So that may be the end of the road for that particular issue.

I got the tail lights flashers to work which was not something I had mentioned as being a problem before because I was pretty sure I knew what was causing it (broken wires behind the seat). With that said the headlights now do not work unless they only work when the engine is running which I don't think is the case.

I'm lost on what to do next with these gauges because any gauge I've ever messed with, if you grounded the wire it would move the needle and none of these did that.