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Alex W 05-23-2013 04:44 PM

Hitachi Alternator rebuild instructions
I have a Hitachi LR155 (55 amp) alternator that I'd like to modify to bypass the internal regulator. I'll be using it with an external 3-stage regulator to charge AGM batteries.

Does anyone have a good reference (online or printed) for doing so?

I'm handy and comfortable disassembling the regulator. I just need some instructions for doing so.


Faster 05-23-2013 06:14 PM

Re: Hitachi Alternator rebuild instructions
On our old Bosch alternator the brush holder/regulator assembly came out with two screws and a simple brush holder installed in its place - it had the pins appropriate for the external regulator connections. Something like that might be available for yours??

Alex W 05-23-2013 06:20 PM

Re: Hitachi Alternator rebuild instructions
I think it will be even simpler. The brushes aren't held by the regulator. There is an exploded diagram here:

I was looking for help knowing which wires to expose for the external regulator, and any tricks like how to retract the brushes when putting back the stator.

Alex W 05-23-2013 06:28 PM

Re: Hitachi Alternator rebuild instructions
I think I found suitable instructions in the manual for the Sterling Pro-Reg-D:

I'm using a similar regulator from Mark Grasser.

Alex W 05-24-2013 12:33 PM

Re: Hitachi Alternator rebuild instructions
I got it apart last night.

It's difficult to disassemble because there is a tight press fit between the bearing and housing and the bearing and spindle. I had to use a gear puller to pull the front cover off, then improvise a pusher to push the rear housing off. Heating the rear housing (it is aluminum) would probably be a better approach, you just have to be careful not to cook the lube in the bearing. The bearings are standard industrial sizes and I had spares, so I replaced them.

One brush is connected to the L terminal (already exposed). The other brush (and the one that I appear to need) is not connected to anything externally accessible, so I needed to add a wire and route it through the back.

The brushes on this don't have real retainers, but there are loops of wire behind the brush housing that can be used to retract them during reassembly.

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