Please can anyone help. I have a John Deere 730D-ES. I have an electrical problem I can’t solve. Brand new wiring harness, complete new switch, new starter button, new rebuilt 24 volt generator. After installing harness and all new components, I have the wire from switch to fuel gauge is 12 volts negative. Everyone I’ve talked to and everything I’ve read tells me it should be 12 volt positive. I can’t get fuel gauge to work with the negative 12 volt. What have I done wrong? All connections have been checked and rechecked and all seem to be right. Please can anyone help me.
- Thread starter roger1940
- Start date
buickddeere
Member
Half of the 12V lights and accessories are 12- chassis. The other half of the lights and accessories are 12V+ chassis.
If you wire everything 12V to run off one battery, nothing will work correct.And one battery will always be discharged and the other battery overcharged.
The generator, regulator and starter are 24V and 24V only. They will work 100% with no connections made anywhere to chassis.
The 12V lights etc use the tap between the middle of the batteries to chassis as a mid point to get 12V.
If you wire everything 12V to run off one battery, nothing will work correct.And one battery will always be discharged and the other battery overcharged.
The generator, regulator and starter are 24V and 24V only. They will work 100% with no connections made anywhere to chassis.
The 12V lights etc use the tap between the middle of the batteries to chassis as a mid point to get 12V.
24 volt isnt my thing, but basically there are A and B voltage power circuits up to the switch, one is from the ungrounded - of one battery, the other from the ungrounded + of the other battery (taken off the big solenoid on the starter I believe), so one is + respect to ground the other is - with respect to ground. Be sure BOTH feeds are at the switch and that the - ground one is what powers up the gauge. There MUST be a frame ground jumper bond wired from where the two batteris are joined in the middle for the 12 volt to work.....
John T
John T
24 volt isnt my thing, but basically there are A and B voltage power circuits up to the switch, one is from the ungrounded - of one battery, the other from the ungrounded + of the other battery (taken off the big solenoid on the starter I believe), so one is + respect to ground the other is - with respect to ground. Be sure BOTH feeds are at the switch and that the - ground one is what powers up the gauge. There MUST be a frame ground jumper bond wired from where the two batteris are joined in the middle for the 12 volt to work.....
John T
John T
Anonymous-0
Well-known Member
Dear Roger,
You state that the wire going to the fuel sending unit is negative. What do you mean by this? If you take a voltmeter and place the positive lead on the chassis and the negative lead on the sending unit wire you should see a 12 volt reading. Is this what you have? This is what you should have, and if you do then you have a problem with the sending unit, the guage, or the guage ground. Let us know what you find.
You state that the wire going to the fuel sending unit is negative. What do you mean by this? If you take a voltmeter and place the positive lead on the chassis and the negative lead on the sending unit wire you should see a 12 volt reading. Is this what you have? This is what you should have, and if you do then you have a problem with the sending unit, the guage, or the guage ground. Let us know what you find.
To Tom43 and any one else trying to help: Take the positive lead from voltmeter and place it on end of wire going to fuel gauge with tractor switch turned on and the negative lead on the tractor frame, I get a negative 12 volt reading. Sending unit and gauge have been tested by using a 12 volt positive from another source.
Tx Jim
Well-known Member
- Location
- Coyote Flats, Texas
Roger,
Are you sure the wires on post A&B on the ing. switch are attached correctly? I think one could reverse them without harming anything because the fuel sender would be the only thing that is negative ground sensitive. Are the wires of the new harness color-coded correctly? Are the feed wires that attach to starter installed on correct post's? Do you have the ground wire attached splitting voltage? Are you sure you have the correct fuel sending unit?
buickanddeere
Well-known Member
Do you have two separate power supplies going to the light switch?
One will be 12+ to chassis, the other 12- to chassis. One half of everything powered from the switch is 12- and the othe rhalf of the loads are 12+.
These two lines have 24V between them and must not touch together. One goes on A and the other on B. I can't recall while being away from my references which of A & B are + and -.
One will be 12+ to chassis, the other 12- to chassis. One half of everything powered from the switch is 12- and the othe rhalf of the loads are 12+.
These two lines have 24V between them and must not touch together. One goes on A and the other on B. I can't recall while being away from my references which of A & B are + and -.
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