Belt/Alternator Output Question

[Ironhead]

I just put a new serpentine belt on my 98 Vortec 5700. Of course, I checked the voltage gauge right afterwards. I had the AC on Max, and my truck has the Daytime Running Lights. I was surprised that the needle was well below the centre point. Also noticed that the alternator pulley was hot, as though the belt was slipping. Turned off the AC, and the needle went up to 14 Volts.

The belt seems to have good tension, the tensioner spring seems good, and the tensioner moves easily.

My question is what voltage do you guys see when the truck is running at low RPM (say 1000RPM) with the AC on max?

Also, is the hot alternator pulley normal? The alternator is a rather feeble looking 100 amp unit.

 

[SAATR]

I usually see around 13.2 to 13.5 with both blowers on full in the Burb. But, I also have an AD244. Swapped out the factory alt because of the low voltage at idle issue. That's measured at the battery with a DMM. Gauge shows just below 14.

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[Ruger_556]

Sounds normal to me. That gauge is not very accurate FYI... Take the belt off and spin the alternator pulley to check the bearings, if they're quiet and smooth I wouldn't worry about it. Alternators make some heat so the pulley will be a little warm.

Normal charging range varies depending on the alternator but I like to see in the neighborhood of 13.2-14.5 volts, it will come up with engine speed and drop with loads but should stay somewhere in that range. If turning the lights and A/C on pulls it all the way down to below 13.0 volts then something is wrong, usually the alternator is at fault but a dead cell in a battery can cause it also. Use a meter to check though, don't trust that gauge.

 

[Ironhead]

Thanks for the replies.

I put a gauge on it at idle, AC off. I got 14.1 volts. I will measure with the AC on Max tomorrow to double check. The gauge reads from 9 v at the low end, to 14 in the middle, so maybe with the AC on max, and daytime running lights on, I should not have worried.

 

[Gambles]

I used to have the same concern, if you don't have much in the way of a stereo system, just adding a 145? I think.. 454 alternator works wonders... think the only thing I had to change was one of the heater core hoses that ran right past it, to loop it up over... and you'll need a 5 dollar plug from autozone to fit the new alternator.. unless I just happen to be the one guy that had the different plug. its been several years now or i'd give a little better instruction.

 

[SAATR]

I used to have the same concern, if you don't have much in the way of a stereo system, just adding a 145? I think.. 454 alternator works wonders... think the only thing I had to change was one of the heater core hoses that ran right past it, to loop it up over... and you'll need a 5 dollar plug from autozone to fit the new alternator.. unless I just happen to be the one guy that had the different plug. its been several years now or i'd give a little better instruction.

The AD244 is essentially what you describe, but is a plug and play replacement for the CS130D that comes comes stock on the Vortec trucks without the heavy duty alternator. The 244 came on the GMT800 2500 trucks, like an 04 2500HD with the 6.0L. The only thing you have to do is bend one of the coolant pipes a bit to clear the larger case, and install a slightly longer K060966 belt. Supposed to be 140a peak output, but the real advantage is MUCH better idle output.

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[Ironhead]

Thanks SAATR for the great advice, with part numbers. The output at idle is obviously a benefit, as these trucks, at least mine, tend to operate at very low revs in normal city driving, and even at 60 mph, the revs are only around 2000.

 

[Sampuppy1]

I need to upgrade my alternator. I took out a cell in my old battery and with a new battery and starter I'd like to make sure the alternator can keep up with the extra lighting demands as well as my very mild sound system. I have future plans for an air compressor and a few more lights including first responder stuff. I need to have a strong charging system. I already run a mtp75 interstate battery, in place of the old mt75. That gives me an extra 200cca.

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Tyler/T-Unit

 

[SAATR]

A group 34/78 battery would have probably been a better choice, due to the larger case size and typically higher capacity. The stronger alternator would benefit too, given that you also upgrade your cabling.

 

[Sampuppy1]

I should do the big 3 upgrade as well.

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Tyler/T-Unit