Alternator draining battery

[NCDiesel]

I have a mid-nineties 753 bobcat. As soon as I got it last year I noticed it was draining the battery just sitting: - within just a week or two. So I made a few checks and sure enough it was losing about 250 mA while the machine was off. I suspected the alternator so I disconnected the alternator and I no longer had a parasitic drain on the battery. My guess was this is because somehow the wiring for the excitation voltage is not going through the ignition switch. So since then I have been disconnecting the battery. But recently I munged up battery cable connector doing it so much, so I've decided it's time to fix it. I have no idea where to start to even look for a wiring issue. Any hints, tips, or tricks? Thanks in advance!!

 

[reaperman]

You could purchase a master shutoff switch to prevent anything draining the battery when turned off. Sometime chasing a small draw is a endless pursuit of trial and error. I wish a master switch would be standard factory item. They aren't too costly either.

 

[Tazza]

You could purchase a master shutoff switch to prevent anything draining the battery when turned off. Sometime chasing a small draw is a endless pursuit of trial and error. I wish a master switch would be standard factory item. They aren't too costly either.

The power to the alternator should go through a diode to prevent battery drain too.
What cable are you removing to stop the drain, the main +ve cable or the small one to excite the alternator?
If removeing the small wire does not fix it, you could have a bad diode on the alternator.

 

[NCDiesel]

The power to the alternator should go through a diode to prevent battery drain too.
What cable are you removing to stop the drain, the main +ve cable or the small one to excite the alternator?
If removeing the small wire does not fix it, you could have a bad diode on the alternator.

To test it, I disconnected the harness from the alternator. To prevent drain I am removing the the battery ground. The reason i think it's the "exciter" circuit and I don't think it's the diode is because it's such a small draw - about 200-250 milliamperes. But enough to drain it in a few/several days. If it was the diode it would probably be a few amps and drain overnight, don't you think? The drain definitely goes away when I disconnect the alternator but it's a harness type plug and so I don't know which of the wires solved it. If it wasn't such a pain to get to I would test by disconnecting the main B+ post on the alternator or use the diode test setting on my multi-meter. I could get a battery disconnect switch from Harbor Freight, but I forget to disconnect the cable often enough as it is, I imagine I would forget to turn the knob on the disconnect too

 

[Tazza]

To test it, I disconnected the harness from the alternator. To prevent drain I am removing the the battery ground. The reason i think it's the "exciter" circuit and I don't think it's the diode is because it's such a small draw - about 200-250 milliamperes. But enough to drain it in a few/several days. If it was the diode it would probably be a few amps and drain overnight, don't you think? The drain definitely goes away when I disconnect the alternator but it's a harness type plug and so I don't know which of the wires solved it. If it wasn't such a pain to get to I would test by disconnecting the main B+ post on the alternator or use the diode test setting on my multi-meter. I could get a battery disconnect switch from Harbor Freight, but I forget to disconnect the cable often enough as it is, I imagine I would forget to turn the knob on the disconnect too

With the power off, can you check if you have power to the excite pin on the alternator? If there is power, it may not be wired correctly to switched power?
The diode i was suspeting was for the excite circuit, but it should be wired to switched power so engine off, it should draw no power...