Changing Alternaror

[Daren Todd]

If I understand your post correctly, your running power to both terminals on the alternator from the starter?

Usually the alternator will get power from two sources. One from the starter to the main terminal on the alternator. The other is from a keyed source going to the exciter terminal. This way it only has power to the exciter side when the key is turned on. The exciter side of the alternator acts as an on switch for the charging system

Alternator can still test good at the auto parts store and still have an internal short causing a small drain. Will usually show up as a small drain on the main power side of the alternator.

 

[olthumpa]

Daren, thanks for the reply.

Yes, I am running power to both terminals on the alternator from the starter.

I took it to a shop that specializes in rebuilding alternators and starters. I have used them for over 30 years but what they told me did not make sense. I was going to do as you suggested and run a lead from after the switch to the alternator but had it tested first and received the following advice: I asked him about permanently attaching a wire after the switch to the alternator - he said that doing that would cause the alternator to constantly charge the battery damaging it. To me, that does not sound correct but I am by no means an expert on automotive wiring.

"Alternator can still test good at the auto parts store and still have an internal short causing a small drain."

How can I test for this?

"Will usually show up as a small drain on the main power side of the alternator."

With the engine off I am not able to measure any amperage draw from the main power side of the alternator. I am measuring an amperage draw from the exciter terminal.

 

[Daren Todd]

I'm actually a little confused by the advise you recieved. All automotive alternators have a dedicated wire to the exciter side that's powered by a key switch. Power is supplied to the exciter side constantly while the key switch is on. And the alternator itself usually has an internal regulator to manage whether it over charges or not.

To test for the small drain I was talking about, is the same test you did in your earlier post. By checking the battery and seeing if there is a small voltage drop over a period of time. And systematically disonnecting stuff to figure out where it's coming from like you did earlier

I'm thinking that if you hook the exciter wire up so it's powered by the fuse block, via the key switch it should take care of your issue. But I do recommend running the wire through a fuse so if the alternator shorts out, it won't wipe out the key switch

 

[Tooljunkie]

There have been many occasions where a small parasitic drain will go away when power is disconnected. Will come back as soon as alt runs and stops.
I use a battery disconnect inline with a DVOM bridging the disconnect. This way the circuit is never opened to keep test consistent.

Please forgive me if im incorrect,R terminal goes to external regulator, no?
With it connected for a period of time, alternator would get warm, if not hot. Its energizing the alternator.

 

[olthumpa]

Daren & Tooljunkie, thanks for your replies.

I'm actually a little confused by the advise you recieved. All automotive alternators have a dedicated wire to the exciter side that's powered by a key switch. Power is supplied to the exciter side constantly while the key switch is on. And the alternator itself usually has an internal regulator to manage whether it over charges or not.
The alternator has an internal regulator. This is the alternator I installed. http://www.ebay.com/itm/291131509604...%3AMEBIDX%3AIT . . . . .

I'm thinking that if you hook the exciter wire up so it's powered by the fuse block, via the key switch it should take care of your issue. But I do recommend running the wire through a fuse so if the alternator shorts out, it won't wipe out the key switch
I have everything ready to do just that, just need to make the connection at the fuse block. Ran extra wires when I did the rewiring.

There have been many occasions where a small parasitic drain will go away when power is disconnected. Will come back as soon as alt runs and stops.
I use a battery disconnect inline with a DVOM bridging the disconnect. This way the circuit is never opened to keep test consistent.

Please forgive me if im incorrect,R terminal goes to external regulator, no?
The alternator has an internal regulator. The original regulator on the tractor has been eliminated. Right now, the R terminal is connecter to the starter, I am measuring the parasitic drain from that connection.
With it connected for a period of time, alternator would get warm, if not hot. Its energizing the alternator.
If I understand you correctly, the alternator would get warm/hot if it was connected to an external regulator. Or are you saying if I connect a wire from the fuse block to the alternator to excite it, it would get warm/hot ?

 

[North Idaho Wolfman]

Sorry but the advice that you got from the shop was a little off.

The exciter wire charges a coil to become a magnetic field, hench why if left hooked to battery when not running it will drain the battery.

The output power is controlled by the internal regulator on that model so no need to worry about it putting out too much.

So like others have said wire it to the run side of the ignition switch and you be fine.

 

[olthumpa]

Daren, Tooljunkie & Wolfman thank you for your wisdom, insight and replies.

I have connected the R - exciter terminal from the alternator to a fuse that is after the main switch. The tractor starts as it should. No measurable parasitic drain. No smoke or sparks - well at least not yet . Took a voltage reading off the battery when everything was done and will compare in the morning, I do not expect any problems.

Again, thanks for all your help.

 

[olthumpa]

UPDATE

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