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Case 580c trans oil temp guage/probe

Yamz

Member
Joined
Apr 22, 2022
Messages
12
Location
United States
I was blazing a trail on the property last week and some honey suckle got under the machine and ripped the wire off the transmission temp sending unit. No big deal, the sending unit didn't work anyways (lol), but strangely, after the wire was ripped off, the gauge went immediately to full red hot like it does when you ground it out during testing. Before that, the needle on the guage just hung all the way to the low side in the yellow. So today I installed a new sending unit, and after hooking the wire back to it, there is no change and the gauge still acts like it is being grounded. The weird part is, when I take the wire off the sending unit, it still does it.

I thought maybe the brush damaged some other wires under the machine related to the power shuttle, but I couldn't see anything damaged or even anything else that looks like it's part of that sending unit's circuit. It looked like a pretty simple setup, sending unit with wire leading to the gauge in the dash. So I'm stumped on this, I don't even see how there could be any response to the gauge whatsoever when the wire is disconnected.

In the wiring diagram, 'LL' is the sending unit, and the wire (16) runs from sending unit to the harness plug (I bypassed the plug) and to terminal 11 on the plug, which traces to the gauge 'I'.

Anybody have any ideas on what I can look at or what tests I can do to track this down?
 

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Last edited:

stinky64

Senior Member
Joined
Feb 25, 2017
Messages
1,367
Location
java center ny
Occupation
big truck wrench/fixer of things
Did you remove the connector from the back of dash cluster? May have damaged one of the foil "tabs" in connector. When you bypassed the plug did you switch any wires? Couple of functions in my dash have never worked due to damage from previous owner. If you're really concerned mount mechanical guages to r/s of dash, that's how I remedied my issues. Availability of reasonably priced replacement was nonexistent at the time did mine.
 

Yamz

Member
Joined
Apr 22, 2022
Messages
12
Location
United States
No I haven't removed the connector from back of dash cluster yet, I will check that when the rain lets up and see if it got damaged or moved out of place when it was yanked on by the brush.

Only reason I bypassed the shuttle harness plug for that sending unit, when I rewired the machine, is because the rest of the harness is working fine (like the clutch cutout button and solenoid on power shuttle works normally) and it didn't look like it 'needed' to go through that plug for the gauge to function correctly. Plus, the old sending unit wire was already broken off (probably happened the same way from brush lol) and I didn't want to bother with that old plug because chances are I would end up having to make a whole new harness. I'll probably make a new shuttle harness one day but for now I have more important repairs to focus on. But no I did not change any other wires in that harness when I did that

And yea it seems impossible to find new gauges that are the shape and size the case 580c dash cluster uses, which is surprising because it seems like you can find most other parts pretty easily. I bought a new circuit board from minnpar when I first rewired the machine. Luckily all my gauges actually worked and the only sending unit that tested bad was the transmission temp.
 

Yamz

Member
Joined
Apr 22, 2022
Messages
12
Location
United States
Ok so I removed the connector to the dash cluster and saw no issues, no damaged tabs or prongs or wires, everything seems normal. I'm tracing every wire in the shuttle harness and not seeing anything damaged or broken or anything that even looks like it is related to that temp gauge. It boggles my mind that the gauge is still being grounded or responding in any kind of way when the wire isn't hooked up to the sending unit or touching anything on the machine. I even disconnected the wire at the sending unit and from the gauge and gauge is still being grounded. Everything else on the dash is functioning normally.

Only thing I noticed out of the ordinary is that the needle for the gauge is very flimsy compared to all the other needles, the ones for water temp, volts, and fuel level are much 'stiffer'. I can actually move the needle for the trans temp just by tapping on the glass a little. Is it possible the gauge is just shot?
 

melben

Senior Member
Joined
Jan 14, 2008
Messages
1,043
Location
Williamsport, Pa
Occupation
Retired 50 Yrs with Case dealership
Those gauges rarely move under normal operation, put it in high gear, lock the brakes or put against a tree and rev it up in forward 4 th gear and I'll bet in a minute or two the gauge will register. Worked many years on hundreds of those and what you describe is normal
 

Yamz

Member
Joined
Apr 22, 2022
Messages
12
Location
United States
Yea I haven't actually used the machine for anything since I put the new sending unit on, maybe I should have driven around a bit first before worrying something was wrong. Here is a video of what I was describing, I manually moved the needle to the yellow before this was taken. The way it moved when turning the key on made me think I had a ground fault somewhere because that is how the water temp gauge behaved when I grounded it to test if it was working.

When I get a chance I'll drive around with it and try the tree test you mentioned (no brakes yet lol) and see if things change once it's all warmed up

 
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