Super hot alternator!

Denisefwd93 · May 7, 2018

On Startup and running,

somebody replaced ground wire but the original ground wire is laying down by the inner fender I think we will reconnect it. No idea why they put in a "new" red ground wire either, duh.

adsm08 · May 7, 2018

I put a new red ground on because it was $.05 and the black on was $11.

Denisefwd93 · May 8, 2018

Lol on the red,

Well, did some checking and some parts installing today, the original ground wire does have some resistance to it.

We took a jumper cable right from the alternator Mount directly to the negative terminal.

Found a ground strap that was
apparently removed, when the engine or transmission was out of the truck buy a previous owner.

It seems to be charging okay. But It's fluctuates very slightly and if the lights are turned on, the dashboard voltmeter drops. I don't have a digital multimeter.

As soon as the engine starts, the alternator gets hot and within a minute you can't touch it! it spins okay so I'm thinking... Diodes?

You can actually smell the windings in the alternator making that pungent smell even though it's not making smoke and it's not really hot outside yet. I do know, just like electric motors alternators run a certain temperature above the ambient temperature.

I guess we'll take it off tomorrow and take it in and have it tested. I don't see any reason to go to a 130 amp on this.

RonD · May 8, 2018

Alternator generates Alternating Current(AC) on 3 Field windings in its case.
Each Field has 2 Diodes to change AC to DC Volts
Outside of the bearings the Fields/diodes are usually what fails.

Each Field generates 1/3 of alternators AMPs, so a 90amp alternator would make 30amps per field, we are getting to the point soon, lol.

Alternators can only generate 1/2 their amps under 1,000 engine RPMs, full AMPs at about 1,800 RPMs

So a vehicle maker specs in an alternator that can run ALL stock electrics at idle, head lights on, blower on high, doors open, ect......
So if you had a 90 amp stock alternator your vehicle would draw about 40amps running with all electrics on.
If you loose a Field then your alternator can't put out 40amps at idle, usual symptom of that is dimming head lights at idle, NO, it is NOT normal, lol.
But as long as you don't idle for hours at a time it will be fine, above say 1,200 RPMs all is well, you have enough amps

If you loose 2 fields then alternator will get very hot as it tries to recharge battery and generate the 40amps or even 20amps at idle, with 1 Field working

Be careful with auto parts store tests, they just look for output so can say an alternator is OK when it isn't

Denisefwd93 · May 8, 2018

This is first time I've ever encountered a hot alternator, there is plenty of air movement from the engine fan and its built-in fan but it still gets hot and like I said you can smell the windings. I don't think an undersized battery would cause this would it Ron? Seems to start and hold a charge which is usually all battery needs to do, I think,.

RonD · May 8, 2018

Engine/key off
Test voltage at battery
Should be 12.3-12.8volts, remember it

Test voltage at B+(stud on back of alternator) to alternators case, should be exactly the same as battery voltage

Unplug 3 wire connector, test yellow wire to alternators case, should be exactly the same as battery voltage.

Test Green wire to alternators case, should be 0 volts
Turn on Key
Test Green wire to alternators case, should be Battery volts now

Vehicle wiring for alternator is 100% if above is true

Denisefwd93 · May 9, 2018

RonD said:
Engine/key off
Test voltage at battery
Should be 12.3-12.8volts, remember it

Test voltage at B+(stud on back of alternator) to alternators case, should be exactly the same as battery voltage

Unplug 3 wire connector, test yellow wire to alternators case, should be exactly the same as battery voltage.

Test Green wire to alternators case, should be 0 volts
Turn on Key
Test Green wire to alternators case, should be Battery volts now

Vehicle wiring for alternator is 100% if above is true

Omg it only took like 10 minutes not even to take the alternator out. The wiring was not scorched the bearings are kind of growling. going over to Napa this afternoon to pick up a lifetime guarantee rebuilt, I'll update this soon as things are back together here's hoping!

Denisefwd93 · May 9, 2018

SUCCESS! lol got the Napa lifetime warranty alternator, double checked all the connections! The little plug is that the Exciter wire? Is a little loose but stays in place.

I took a deep breath, closed my eyes (I have these visions of mob bombs exploding underneath the driver seat even though I never been in the mob)

The beast started right up, and the charging Needle on the dashboard shows that it's charging the battery.

Checked the voltage before and after, it's not digital but best interpretation of the analog needle tells me it was around 13+ The alternator stayed cool until the engine warmed up and it got very warm but not so warm that I can't touch it which, I think is normal for an alternator,

so, that's another item checked off the list yay!

ericbphoto · May 9, 2018

congratulations. That does sound much better.

Denisefwd93 · May 11, 2018

ericbphoto said:
congratulations. That does sound much better.

Yes it seems to be much better, even drove the beast to the shop to get the fan clutch changed. Driving back I find out the front brakes are dragging so it's back in the backyard again LMAO

Doofy · May 11, 2018

It sure feels good when you troubleshoot and actually solve a problem. This builds self esteem and pride in one's ability to do things for one's self. It is wonderful that folks are willing to offer knowledge and advice to point you in the right direction. Great Job!

Denisefwd93 · May 11, 2018

Thanks! But I'd rather not be a car n truck mechanic lol I love my Wooden Boats and canoes way more,

Doofy · May 11, 2018

Denisefwd93 said:
Thanks! But I'd rather not be a car n truck mechanic lol I love my Wooden Boats and canoes way more,

Yes, but when your vehicles are up to snuff, :yahoo:

you can devote more time and effort to your passions. Win win.

Super hot alternator!

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