Installed a lower amp alternator

[bigmike75]

I have an '03 Yukon XL and last June (2010) my alternator went bad on it. I replaced it with a 105A alternator only to find out today that it originally came equipped with a 145A one. Is is safe/wise for me to continue using the lower powered alternator, or should I swap it out for the correct one? I am not running anything special/custom on my truck (a new head unit is all I added, but using the factory Bose amp and speakers). Thanks for anyone's help on this...

 

[blueflamed03]

well your almost at a year, so I say your fine. It will run, just may have to work harder to keep on the current pull on your vehicle...but, I'd say its a no brainer to just keep pluggin away with it.

 

[2005yukonxl]

ditto. and dont do it again.

 

[bigmike75]

Thanks guys for the quick responses!

 

[chip]

Go high amp next time.

 

[Jay]

The trucks used the 105amp alternator, while the SUVs got the 145amp alternator (i think starting in 2005 they increased these outputs, respectively, due to the 400watt load of the electric fans). The biggest difference in electrical load on the trucks versus the SUVs comes from the rear HVAC, DVD, and Bose subwoofer system in the SUVs.

Remember, you're only dealing with 12-14 volts in these vehicles.

Using Power (Watts) = Volts x Amps,
- 105A at 14 volts gives 1,470 watts
- 145A at 14 volts gives 2,030 watts

So about 600 watts difference in power output. I'll bet that most of that is used to power the rear HVAC and DVD systems with a little bit left over to power other stuff (game consoles, inverters, etc).

If you find your headlights dimming during night time driving when turning these systems on and off, you probably will want to change back to the 145A alternator since if the 105A can't keep up, the battery will be forced to supply the extra power. The starting batteries in these trucks are not meant to supply long term power like a deep cycle battery, and long term loads will shorten the life of the battery considerably since starting batteries have thin lead plates, whereas a deep cycle has very thick plates (but can't put out the same peak loads).

Just keep a watch on your battery voltage and electrolyte level (if you can check it, some batteries nowadays are fully sealed). If either of these are slowly deteriorating, you will have to swap back to the 145A.

 

[chip]

The trucks used the 105amp alternator, while the SUVs got the 145amp alternator (i think starting in 2005 they increased these outputs, respectively, due to the 400watt load of the electric fans). The biggest difference in electrical load on the trucks versus the SUVs comes from the rear HVAC, DVD, and Bose subwoofer system in the SUVs.

Remember, you're only dealing with 12-14 volts in these vehicles.

Using Power (Watts) = Volts x Amps,
- 105A at 14 volts gives 1,470 watts
- 145A at 14 volts gives 2,030 watts

So about 600 watts difference in power output. I'll bet that most of that is used to power the rear HVAC and DVD systems with a little bit left over to power other stuff (game consoles, inverters, etc).

If you find your headlights dimming during night time driving when turning these systems on and off, you probably will want to change back to the 145A alternator since if the 105A can't keep up, the battery will be forced to supply the extra power. The starting batteries in these trucks are not meant to supply long term power like a deep cycle battery, and long term loads will shorten the life of the battery considerably since starting batteries have thin lead plates, whereas a deep cycle has very thick plates (but can't put out the same peak loads).

Just keep a watch on your battery voltage and electrolyte level (if you can check it, some batteries nowadays are fully sealed). If either of these are slowly deteriorating, you will have to swap back to the 145A.

+1 Another great post Jay!

 

[Bedore]

My 2001 came with a 130amp alternator. It has recently begun to fail and when I looked up the alternator, I had the choice of 105 or 130. Obviously I went with the 130A but did not see a 145A listed. Did GM switch to the 145A on later vehicles?

 

[bigmike75]

The trucks used the 105amp alternator, while the SUVs got the 145amp alternator (i think starting in 2005 they increased these outputs, respectively, due to the 400watt load of the electric fans). The biggest difference in electrical load on the trucks versus the SUVs comes from the rear HVAC, DVD, and Bose subwoofer system in the SUVs.

Remember, you're only dealing with 12-14 volts in these vehicles.

Using Power (Watts) = Volts x Amps,
- 105A at 14 volts gives 1,470 watts
- 145A at 14 volts gives 2,030 watts

So about 600 watts difference in power output. I'll bet that most of that is used to power the rear HVAC and DVD systems with a little bit left over to power other stuff (game consoles, inverters, etc).

If you find your headlights dimming during night time driving when turning these systems on and off, you probably will want to change back to the 145A alternator since if the 105A can't keep up, the battery will be forced to supply the extra power. The starting batteries in these trucks are not meant to supply long term power like a deep cycle battery, and long term loads will shorten the life of the battery considerably since starting batteries have thin lead plates, whereas a deep cycle has very thick plates (but can't put out the same peak loads).

Just keep a watch on your battery voltage and electrolyte level (if you can check it, some batteries nowadays are fully sealed). If either of these are slowly deteriorating, you will have to swap back to the 145A.

Thanks a lot Jay! I do notice my voltmeter gauge moving back and forth just a little while driving. Additionally, when rolling up or down my windows I do notice headlight dimming. I guess that means I should be upgrading the alternator?

 

[Jay]

The voltmeter will move around some with engine speed since the alternator generates power based on shaft rpm. Even with a good system you may notice some immediate dimming with the transfer of power kicking in, but after wards you should notice everything running normally. Earlier I was referring to lights being noticeably more dim while all systems are on.

A fully charged battery, after sitting for an hour or so, should show 12.8 volts with no loads on it. Around the 12.2-12.5 range is where it's going "dead". Run it until 10-11 volts and permanent damage happens. Take care of those batteries and they'll serve you well.