Alternator Failing from RPM?

wesinls

wesinls

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Lost voltage yesterday and pretty sure it's my alternator...if I tap it with a wrench, or wiggle around the one wire connector the voltage fluctuates and at times goes above 15 and engine quits.

It's a new AC Delco.

So...any truth to RPM causing alternators to fail? Engine has a redline of 7000...i like the power up high and am pushing the motor, so I'm only assuming at this point that's what caused my issue. Reading various forums online this seems to be a common problem?

What are reputable brands to go with for an alternator? I do not need some 600 dollar black 250 amp show piece...just something in the 150ish range that's higher quality than an AC Delco.
 
Absolutely RPM can kill it.
Has been discussed on here a few times.
Going to a bigger pulley really helps.

Have you added up everything to ensure 150 Amps is enough?

I added up all of my stuff just to run my engine, so no lights/radio, and I am at 134 Amps.
I was burning up the stock AC Alternators fast.
So I went to the 250 Amp alternator from CBM.
 
wesinls said:
Lost voltage yesterday and pretty sure it's my alternator...if I tap it with a wrench, or wiggle around the one wire connector the voltage fluctuates and at times goes above 15 and engine quits.

It's a new AC Delco.

So...any truth to RPM causing alternators to fail? Engine has a redline of 7000...i like the power up high and am pushing the motor, so I'm only assuming at this point that's what caused my issue. Reading various forums online this seems to be a common problem?

What are reputable brands to go with for an alternator? I do not need some 600 dollar black 250 amp show piece...just something in the 150ish range that's higher quality than an AC Delco.
Click to expand...
here is the deal.......LS stuff runs at about a 3:1 ratio of crank speed vs alternator speed to get max output from the alternator. this is easy to see by the diameter of a LS crank pulley vs the alternator pulley, and most other OEM's are within this range as well.

However, most daily drivers never see the extended higher RPM ranges that your sand car motor does and that is why you will see bearing failures in some cases. but most times its sand getting in there that does the most damage and is the real cause of most alternator failures. next up is undersized wiring or poor or no grounding of the alternator causing the alternator to build up excessive heat.

there is nothing wrong with the OEM GM stuff if it has the amperage output to support your total electrical load. slowing the alternator down with a large pulley just reduces the alternator output. this was an old school drag racing trick to look for every last bit of horsepower.

depending on how old your alternator is, you likely would just chalk this up to the cost of doing business in a harsh environment. genuine OEM parts are tough to find nowadays with so many low cost counterfeits.
 
Alternators ,in general,have about an 18000rpm redline. Adjust your pullley ratios to keep it safely under 18k,MAX. I run 4-7k almost constantly for hours without issue after I got alternator education and my ratios right. Your charging may suffer at low engine rpms but that is how it is if you want your alt to live a long happy life.
 
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