Alternator Replacement

[Chuck Wheeler]

Don,

I believe that you will se the benefits of two alternators when you are
using a lot of the 12 volt systems on your coach such as moving out after
spending the night dry camping on the the batteries. When just charging the
batteries there are several things that will come into play limiting the
charging current. First you have the internal resistance of the batteries.
This increases as they age and the charging current will go down no matter
how much they are discharges. Then there is the resistance in the charging
circuit, wiring, ammeter shunts , etc.. Also no two regulators are exactly
the same. So one alternator will take the load first. It will be somewhat
balanced by the resistance in the wiring between the two. When I would
check out construction equipment with two alternators I would test one at a
time by disconnecting the battery wire from one alternator at a time.
Sometimes we would discover problems in one circuit. As I said at the
beginning the real benefit will be under heavy load. Just charging the
batteries this current will be limited by the alternator and wiring. Up to
the point that you overload the alternator the charging current will remain
the same for a certain amount of battery discharge no matter how large an
alternator you install.

- Chuck Wheeler -
82 FC 31 SB
Fort Worth, TX


_____

From: WanderlodgeForum@yahoogroups.com
[mailto:WanderlodgeForum@yahoogroups.com] On Behalf Of Don Bradner
Sent: Sunday, March 04, 2007 11:07 PM
To: WanderlodgeForum@yahoogroups.com
Subject: [WanderlodgeForum] Alternator Replacement



My alternator replacement job is done, I'm happy to say.

For memory refreshment, I had Alternator 1 with zero output, and Alternator
2 with max 50-amps and unable to maintain voltage with headlights on.

Replacing the top-front one (under the bed) was easy. That one was a 130-amp
Prestolite. After replacement, and with the power cables removed from the
back one, the engine was started and showed 100 amps on Alternator 1 at
idle, zero on Alternator 2. Voltage was above 13.5 and amps dropped quickly
as the start drop was replaced, even with the headlights on.

Replacing the back alternator was not easy at all. It sits under the A/C
pump, so I tried to drop it out the bottom, but there just wasn't room to
make it. The way the A/C pump is bracketed it was a B***h to remove, and
similar to replace, but I eventually got it done. The removed alternator has
no apparent markings anywhere, so I don't know what it was or its rating.

Running with the two new Leece-Neville 160-amp alternators the output after
startup is still 100 amps, shared equally between the two. I guess that
makes sense, but I had thought it would be higher. I wish I had a way to
draw down the batteries and still have enough to start the engine, so I
could see if it would show a higher charge rate.

Overall it was an interesting learning experience. I also replaced the belts
on Alternator 1, which showed some wear, but the others - alternator 2 and
the A/C pump - looked like new so I left them.

Don Bradner
90 PT40 "Blue Thunder"
Eureka, CA






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