Keep "Frying" alternators.

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Rjonesy
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Keep "Frying" alternators.

Postby Rjonesy » Fri Feb 07, 2020 6:49 am

In the past 6 months or so I've gone through 3 alternators. Seems to be frying the rectifier or regulator. I've added an electric fan, lift pump when I swapped to a duramax fuel filter, and some led lights (replacing originals so this should be a net lowering of load). I have the LS console so am able to monitor the voltage meter and have not noticed significant draw down. This time I checked alternator output with a multimeter and it shows 15+ Volts with no load at idle but when connected to the system only battery voltage. Would appreciate any help.

Thanks!

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Red Truck
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Re: Keep "Frying" alternators.

Postby Red Truck » Fri Feb 07, 2020 2:02 pm

Was this occurring before you installed the fan and pump? If not, then my guess would be to disconnect each of those components, run it at idle, and look for a drop in the excessive draw on the battery to try to isolate the culprit. 15+ volts sounds like a lot, as if your battery is gasping for a charge. I'm a 'gasser', so I'm not familiar with the Lift Pump application. I might add that reverse polarity will ruin a rectifier and/or (modern day) voltage regulator, as in connecting up a battery charger wrong. Hope I could help!
'87 Isuzu p'up 2.3 gas, 5spd, 4WD, base model, Fed spec

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Rjonesy
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Re: Keep "Frying" alternators.

Postby Rjonesy » Fri Feb 07, 2020 3:52 pm

No. The 15V was with the alt. disconnected and just the meter on it. When plugged in it has no output. Something going on with the regulator it seems.

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Rjonesy
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Re: Keep "Frying" alternators.

Postby Rjonesy » Fri Feb 07, 2020 3:53 pm

Everything was working for a good while until the first failure. Since then alternators lasting at most a couple months.

minidiesel
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Re: Keep "Frying" alternators.

Postby minidiesel » Fri Feb 07, 2020 4:39 pm

I'm with red truck on this. Process of elimination. I have done the same, led, electric fan and lift pump and I'm ok. So isolate and diagnose.
1986 Isuzu pup long bed diesel 5 spd 2 wd .
1986 winnbago lesharo Renault turbo diesel.

minidiesel
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Re: Keep "Frying" alternators.

Postby minidiesel » Fri Feb 07, 2020 4:42 pm

Where did you connect brown wire for electric fan(switch/ignition wire).? I went back to battery for simplicity and after shut down cool down.
1986 Isuzu pup long bed diesel 5 spd 2 wd .
1986 winnbago lesharo Renault turbo diesel.

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Red Truck
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Re: Keep "Frying" alternators.

Postby Red Truck » Fri Feb 07, 2020 5:20 pm

I neglected to add: Is the battery in good order? A weak or defective battery 'on its way out' can ruin an alternator.
'87 Isuzu p'up 2.3 gas, 5spd, 4WD, base model, Fed spec

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Rjonesy
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Re: Keep "Frying" alternators.

Postby Rjonesy » Tue Feb 11, 2020 12:54 pm

When I get a chance I’ll try to isolate circuits. Although as I mentioned it didn’t seem to show a big draw on the voltmeter. First need to deal with the massive slab leak in our house and then fix the alternator. Right now running off the battery and charging every couple days. Just sold other vehicle so this is my daily. With power steering and turbo it’s a real pain getting to that alternator!