1st Time I Have Every Seen This

[Michael]

I have been plagued by a fuse blowing problem on my ZL1801 in the charging circuit. I finally started working today to isolate the problem with my tester. I disconnected one item at a time and finally found the problem after the 2nd item that I tested.

I have never seen in over 35 years of working on vehicles, tractors or heavy equipment what was blowing a fuse quite like this. It was a dead short in the oil pressure switch. The instant I would put a fuse in it would pop it. I figured that I had a dead short someplace else on my tractor that is 30 odd years old.

Because I thought about it to much and refused to believe that the pressure switch was bad I retested it after I had it off the tractor. With my ohm meter it pegged out with no resistance.

I went to the Kubota dealer and got a new switch and installed it and another new fuse and tried again. It DID not pop the fuse and I got the light on for a moment at startup and it the light went out and the tractor is charging.

So that is a bit of a surprise that the oil pressure switch is in the charging curcuit but it is in some weird way.

So for $26.00 I fixed the tractor and ended up not tearing the entire wiring system apart to find a problem.

 

[aquaforce]

Very interesting.
Thanks for posting this.

 

[Michael]

I still can not figure out why it was blowing the fuse but it was. Looking at the wiring diagram in the Work Shop Manual for a L185 it was tied into the ignition switch on a different circuit. I just was testing everything and for some unknown reason I hit on the problem.

The only thing I can think of is maybe in the dash the wiring is crossed someplace or the ignition switch is causing back feed into the charging circuit but then the dash light would stay on all the time. As long as it works and everything else is working I am not going to mess with it.

The dash light for the charging system has never worked in the 5 years that I have had the tractor but I did test the charging with my tester and the alternator is putting out 25 amp and 14.3 volts so it is now working properly.

Wiring is something I hate as I had more head scratching from it then anything else.

 

[Wildfire]

I still can not figure out why it was blowing the fuse but it was. Looking at the wiring diagram in the Work Shop Manual for a L185 it was tied into the ignition switch on a different circuit. I just was testing everything and for some unknown reason I hit on the problem.

The only thing I can think of is maybe in the dash the wiring is crossed someplace or the ignition switch is causing back feed into the charging circuit but then the dash light would stay on all the time. As long as it works and everything else is working I am not going to mess with it.

The dash light for the charging system has never worked in the 5 years that I have had the tractor but I did test the charging with my tester and the alternator is putting out 25 amp and 14.3 volts so it is now working properly.

Wiring is something I hate as I had more head scratching from it then anything else.

I've done allot of electrical work in my trade and still do and I've never seen it. My experiences with sending units they either don't work at all or go full gauge when defective. Must be wired in some weird way to pop a fuse. Did the wire running to the gauge or sensor get battery voltage applied by accident? Was there an improper wiring repair done to the machine to cause that to happen? Somethings up. Never heard of it.

 

[Michael]

I checked the wiring and can not find a reason or anything improper with the wiring. I do think that I will look at and test the ignition switch and see if it is a problem. All the sensors I have seen over the years have always failed by not reading or giving a false reading as you described Wildfire and not a dead short.

Since this only powers a idiot light I am not to concerned about it and if it happens again I can always simply tape off the end and install a gauge.

 

[Wildfire]

I checked the wiring and can not find a reason or anything improper with the wiring. I do think that I will look at and test the ignition switch and see if it is a problem. All the sensors I have seen over the years have always failed by not reading or giving a false reading as you described Wildfire and not a dead short.

Since this only powers a idiot light I am not to concerned about it and if it happens again I can always simply tape off the end and install a gauge.

I can't see why or how the switch could cause the problem. The wire going to that sender (sometimes called a switch) is only a ground wire. As soon as the switch closes it completes the ground and the wire is grounded then. Now seeing that the wire has a ground the idiot light has 12 volts waiting there at all times and when the ground that's supplied by the sender kicks in the light comes on. I've never seen battery voltage to a sender for an idiot light.

On certain vehicles I've seen 12 volts present at sensor such as an oil pressure sensor. The 12 volts was present just in case the fuel pressure relay failed. If the relay failed in that case when you would crank the motor the oil pressure switch would eventually supply the 12 volts to the fuel pump after the oil pressure built up. It's kind of like a back up system to keep you from being stranded.

In your case it's a much simpler system. 12 volts to the light and a ground to the switch.


That's the way I see it anyway

 

[Michael]

The issue came back today and I found the problem. The original oil sending unit was bad and has been replaced.

I was using the tractor today and found when I hit a bump the fuse popped. I went back into the wiring and found the problem. The wiring harness had a section of it that was worn off and had been rubbing against the inside of the dashboard. I found that the wires common to the regulator and the oil sending unit were side by side and each had been rubbed though the insulator. The wires were long enough that I cut out the damaged area and splice them back together and soldered them and then used some heat shrink on the wires and then tape, then plastic guard in the area. I also rerouted the wiring away from the area that has some sharp metal on it, but to make sure I also installed some plastic edge molding on the sharp metal that I had handy and glued it on with some 3M spray adhesive.

Did I ever say that I hate wiring has I have always had to do some head scratching to figure it out.

 

[aquaforce]

That sounds more typical.

Glad you found it. Good job.

 

[Michael]

The only bad part is the fact it took me 10 minutes to find the problem and 3 hours to fix it. I only had about 6 inches to work in without tearing apart the entire dash and I still had to take the hood off to get room enough for me to lay across the front of the tractor and to reach in under the dash.

 

[Greg]

The only bad part is the fact it took me 10 minutes to find the problem and 3 hours to fix it. I only had about 6 inches to work in without tearing apart the entire dash and I still had to take the hood off to get room enough for me to lay across the front of the tractor and to reach in under the dash.

Could have been worse. I was taking my tractor out for a test ride yesterday and decided to top off the steering box with gear oil before I pulled out. 2 minute job. I dropped the plug around the transmission and the frame and it took me nearly 2 hours to find it. 1.5 hours in i got so annoyed, I stopped for lunch. I found it on the floor. Not that i didn;t look there, but it was a good 12-14 feet away. I was very frustrated.

That's the last time I'll do any maintenance in my tractor!