Hour meter electric power from what location

Last fall the electric power to the hour meter on my CAT D3C dozer with 2921 actual hours on it stopped powering the hour meter. There was no power in the wire to the hour meter.
Last Fall I tried taking power from dash lights to power the hour meter but the meter would run all the time from the light connection on the dash so I took it off the light connection all in with in one hour of time so no excess hours on meter.
Then early this spring I installed a wire from the alternator where the cable from the battery connects to directly to the hour meter; I had no battery in the machine then. Later during May I put the battery in the dozer and moved it out of the storage building. The employee was operating the dozer and did not notice the hour meter sky rocketing in usage over the say 20 hours it has been used since battery put in. The meter now reads 4,577 hours, so it is continuously being powered. I toke the wire off the alternator so no more hours would be recorded.
Question is where can I get power from on the dash to power the hour meter when the master switch is on/engine running?
Next question it there a way to reverse the hours on the meter so it goes back to the 2921 hours plus 20 hours of usage?
I might have to get a new hour meter and connect it to a battery or trickle charger to bring the new hour meter up to the 2,2921 + 20 hours actual usage.
Thank you in advance.

Post a Serial Number. That way you can get a correct electrical schematic and remove all doubt where the power comes from.

Sometimes it’s from the charging side of the alternator but I’m not prepared to speculate in your case.

Last question first, no way to back up an hour meter. So unless you are really worried about the reading I would just make a label and put it next to the meter saying Subtract "so many hours".

A full serial number might let someone see a wiring diagram to determine where the meter is suppose to get it's power feed.

Looking at one wiring diagram for a D3 that may or may not be like yours it seems that the hour meter is switched on for that one by an oil pressure switch that gets it's power from the output terminal of the alternator.

Factory dipsticks had the meter key connected on a mower I have, all great till someone leaves the key on. Should have been hooked to oil pressure sending unit.

CAT D3C serial number is 6PF00231 year 1989

Well it looks like you are sh1t out of luck. The electronic versions of the schematic are so poor that when they are magnified they lose all clarity. So you are going to need a paper version or get someone who already has one to give you the information.
There are a couple of schematics will do the job for your machine. Either SENR5222 or SENR3812 will work from what i can see.
Other than that and based on the age of your machine it may pay you to register on the ACMOC web site and ask your question there.

As I recall the hour meter is powered off the amp meter and the other wire goes to a oil pressure switch that grounds the hour meter when the engine is running.
Bob

Nige said:

Well it looks like you are sh1t out of luck.

Click to expand...

I was kind of afraid of that myself. When I looked on SIS for just any D3C wiring diagram the quality of the scan made it look like a little kid with a worn out crayon and drawn the schematic.

On one of them I did think I could make out wiring that showed wire from the output terminal of the alternator going to a pressure switch and then to what could have been an hour meter. I know a lot of could be and maybe's there!

Did do a bit of stumbling around in SIS 2.0 , about the only way I find any thing, and I found this note:

SMCS - 1400,1435


D3C (3RF, 6PF, 7JF, 8BF, 5KG, 5ZG, 7JG, 8DG, 1PJ, 4HJ, 5CJ),
D4C (7KG, 9BG, 1RJ, 2CJ),
D5C (6PJ, 3MK) Tractors;
931C (6RF, 7HF, 8AF, 5LG, 9AG, 2BJ, 6AJ, 2AK),
935C (8CF, 5DJ) Track Loaders

The 6N2466 Pressure Switch controls the hour meter and enables the backup alarm on the machines listed. The pressure switch also controls the bucket kick out circuit on the 931C and 935C Track Loaders.

So I guess looking for an oil pressure switch on the engine would be a good place to start. Jumper that assuming it has power to it and see if you now have power getting to the hour meter.

thank you kshansen, I will look for an oil pressure switch.