Now oldtimer is getting close.
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LED headlights, LED running lights, or LED tails.
Nope! All stock except for the amp connected to the battery which was disconnected at the onset.
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The thought of a slipping belt on a pulley crossed my mind earlier but was dismissed as I was having a hard time seeing that causing an alternator to go into overdrive. Normal voltage at idle and battery voltage at elevated RPMs could certainly point to a slipping belt for whatever reason as I went through this a few years back on one of my cars.
The part throwing me is the frying of the alternator and 100 amp fuse because of belt slippage.
Idler trying to seize up?
There are no idler pulley’s for the drive belts. All components utilize jack bolts/screws for belt tension.
But it has to do with the belt.
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Different number of splines as compared to the pulleys? More guessing on my part.
Belts are correct for the vehicle.
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Wood ruff key on crank let go and all accessories turning slow due to slipping pullies ?
Just a wild guess…does not explain the blown 100 amp fuse though
Nope! But you’re really close.
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Belt chaffed a wire, causing a short?
Splines stripped out of the damper?
WE HAVE A WINNER!
Look at what happened. The 100 amp fuse was blown. This caused the alternator to go to full load output. Probably from a bad ECU. Remember it wouldn’t communicate with the scanner?
The alternator created such a drag on the old harmonic balancer that it tore the pulley for the alternator off the rubber isolator on the harmonic balancer. So as the electrical load increased the pulley would slip on the harmonic balancer. So the faster you rev’d the engine the more it would slip and no power would be produced from the alternator. And no, no noise from the harmonic balancer.
So for now, I tack welded the pulley on the balancer for the alternator to the pulley for the AC which will prevent the pulley from slipping until I can find a replacement harmonic balancer. Which RockAuto doesn’t even list. So it should be easy to find.
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Under drive pulley installed for more engine power?
Wow, so was the after market amp the reason for the blown fuse to begin with?
So I was partially correct…the crank pulley was separating, but I didn’t connect that with the full-field load caused by the failed ECM.
I find failed Honda ECMs pretty rare. Any idea as to the cause of the original failure?
All of that grief because of a cheap fuse. I wonder if the vehicle had been jump started incorrectly with the cables being hooked up backwards and that is what led to the blown fuse and who knows what else or the vehicle was operated for a while at elevated RPMs with the alternator warning light glowing and which then led to multiple other problems?
What a mess. 
This is a great problem. Thanks for sharing it.
Two questions:
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Are you saying the outer ring of the harmonic balance - the section that is held on by rubber - is the pulley that drives the alternator belt?
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How did you finally find it - especially if it didn’t make any noise?
Question remaining: What made the 100 amp fuse open in the first place?
Question remaining: What made the 100 amp fuse open in the first place?
That’s a good question. It was described as a battery fuse, meaning either the battery produced over 100 amps of current to some circuit in the car, or the alternator tried to push over 100 amps of current into the battery.
For the latter to happen, the regulator voltage in the alternator would need to be quite high in order to overcome the internal resistance of the battery. If that were the case, wouldn’t it have also blown other electrical components in the car?
[Update:] I’m wondering if a jump with the polarity on the cables reversed, as OK4450 noted, cause that fuse to blow.
The owner was driving the vehicle when the 100 amp fuse blew. That’s why the vehicle had to be towed to the shop.
I think what happened is before the computer died, it commanded the alternator to go to full load amp output. This load from the alternator on the old harmonic balancer caused the pulley for the alternator belt to sheer off the rubber isolator. During this time the 100 amp fuse blew.
At idle, and as more load was applied to the alternator the voltage would drop. This was because the pulley was starting to slip. But at idle you couldn’t detect that the alternator belt was rotating at a slower rate than the other belts. It wasn’t until the engine RPM’s were increased that you could detect the alternator belt was rotating at a slower rate than the other belts. And of course, I didn’t notice this at first because all the previous times I brought the RPM’s up all my focus was on the meter connected to the battery.
If you work in the vehicle repair field long enough you’ll eventually expierience some really wierd things. Or, One For The Books.
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