Alternator Voltage Booster

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So, now my voltage is low on idle and goes up when I gas it (parked or otherwise). Is this due to a dying alternator or is this fuse killing my AGM battery?

I had to jump my LX the other day. Haven't tried since. (Recently went out of town)
 
I say alternator. But you can replace the 7.5 amp fuse and see if it changes. My hunch is it won't.
 
Terrainer said:
So, now my voltage is low on idle and goes up when I gas it (parked or otherwise). Is this due to a dying alternator or is this fuse killing my AGM battery?

I had to jump my LX the other day. Haven't tried since. (Recently went out of town)
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I had similar behavior on my 99 LX about a year ago (non-AGM, and no voltage booster diode), it was a hint that the alternator was on its way out, but not quite dead yet.
 
Installed the GM diode from @cruiserpatch and was expecting higher voltage...

4834.webp


Any ideas?
 
Dirt J said:
Installed the GM diode from @cruiserpatch and was expecting higher voltage...

View attachment 4134769

Any ideas?
Click to expand...
What are your voltages (when you start, and what it settles to) pre and post install of this unit?

For me (I purchased the GM diode somewhere else) my pre values were: ~14.1 when starting and settled ~13.4.
Post values: ~14.5 and settled ~13.8

Just wanted to throw some data points out there. My values are readings at the terminals; my Torque Pro values always seem to be ~0.8v off this value. Don't know what the deal with that is, but it's always been that way for my rig.
 
I will need to do some testing and report back, as I did not document my pre-diode numbers. I also did not realize there is a ramp up/settled voltage swing. I can take readings at the terminals too, if that's more accurate.

Just don't want to kill my new AGM, as my last one died a quick death.
 
TLCPNW said:
What are your voltages (when you start, and what it settles to) pre and post install of this unit?

For me (I purchased the GM diode somewhere else) my pre values were: ~14.1 when starting and settled ~13.4.
Post values: ~14.5 and settled ~13.8

Just wanted to throw some data points out there. My values are readings at the terminals; my Torque Pro values always seem to be ~0.8v off this value. Don't know what the deal with that is, but it's always been that way for my rig.
Click to expand...
You should expect Torque Pro values to be different than those measured at the battery terminals – The BT adapter is connected downstream, through two harnesses. Electricity's is cool and everything, but it ain't free and it ain't magic.

FWIW, there is no "settling" of voltage. What you're seeing is the voltage from the battery and the alternator – two different sources. The battery supplies all the voltage until the engine turns the alternator enough to drive its output. At that point, the alternator is supplying the operating voltage and replenishing the lost battery reserve.
The battery voltage diminishes with time, because it's a finite volume and the alternator voltage changes with engine rpm, because that's what drives the generator. I don't know which alternator you have, so I can't state definitively, but the 100% rated output doesn't happen until well over 2,500 rpm.
 
Malleus said:
You should expect Torque Pro values to be different than those measured at the battery terminals – The BT adapter is connected downstream, through two harnesses. Electricity's is cool and everything, but it ain't free and it ain't magic.

FWIW, there is no "settling" of voltage. What you're seeing is the voltage from the battery and the alternator – two different sources. The battery supplies all the voltage until the engine turns the alternator enough to drive its output. At that point, the alternator is supplying the operating voltage and replenishing the lost battery reserve.
The battery voltage diminishes with time, because it's a finite volume and the alternator voltage changes with engine rpm, because that's what drives the generator. I don't know which alternator you have, so I can't state definitively, but the 100% rated output doesn't happen until well over 2,500 rpm.
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Excellent info from a trusted guru. Thanks Malleus, always appreciate your insight.

For the settled voltage, I see what you're saying; I've just noticed how the voltages react on a day to day basis on my gauges (one being Torque Pro) based on my average day to day driving (checking the next day and not say after starting it up again after 15 minutes) which seemed fairly consistent over the years. Thanks for the description of what is going on here.

Upgraded 130amp 2003+ alternator FYI.
 
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