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Discussion Starter · #1 ·
Ok so, hooking up the volt meter to the battery these are my numbers I got under the set circumstances:

1. At Idle with no accessories on: 14.15
At 2000RPM w/ no accessories on: 14.16

2. At Idle w/ lights on and Hellas: 13.44
w/ lights on and Hellas @ 2000RPM: 14.12

3. At Idle w/ all accessories on: started @ 12.54 then continued to drop until around 12.49 will keep dropping though if I left it
At 2000RPMs all accessories on: 13.07 but will continue to "recover"

What do all think seems to me new alternator is bad? Can't keep up @ idle?
 

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if it were mine i wouldn't worry about it , isuzu's have weak alt's , i think 90amps , as long as you stay above about 12.8v i would think the ecu will work.
 

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What amp rating is this alt?

Alts have a power curv, much like your engine does.

Idle is barely enough to keep the ignition system & onboard computers & maybe headlight/running lights powered, that's about it.

Full rated power levels are not achieved until about 5k rpm for many alts. It looks like you just have a lot of accesory draw.

~psguardian
 

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Discussion Starter · #4 ·
My alternator is not original it is a Reliance.. I was having issues with all my lights after I had the front main seal on my engine done. My lights would dim at idle.. Never happened before.. So I replaced my battery and alternator and did the big 3 with no change so I was suggested that my new alt could be bad as well.
 

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Maybe weak/dirty ground connection? Or you've finally started to see the result of overloading a small alt?

~psguardian
 

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Discussion Starter · #6 ·
I cleaned all the grounds before thinking it was a ground but no change....The thing is, is that even with the hellas off it still is bad when the rear defrost is engaged
 

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Your alt readings a perfect. They are very nearly the same as mine with a factory alt.

So your light problems are coming from another place. I'm still banking on bad connections somewhere that are causing the lights to dim from lack of power. Double check all your grounds, especially the one that looks like a woven strap that goes from the engine to a metal bracket on the firewall.
 

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alt's put out approx 60% of rated output at idle , right at 95% at 2500 engine rpm , don't forget the alt rpm is about 2x that of the engine rpm because of the pulley sizes.

i agree with above , check connections , don't try and tighten them , loosen them , then retighten , one thing i have always done is put a large wire ( 4-6 gauge) from the engine to the body .
 

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yeah same with my alt,

and im running alot of stuff right off the battery mine is around the same.

your connections are good its just when the trucks on idle the alt is not charging as much as it would with higher RPMS.

the reason the volts are lower are because of the accessories your using and the draw. if your alt is bad you would not have 13-14 volts while running thats the way to know if its bad or not.

:)
 

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Discussion Starter · #10 ·
do any of you have dimming lights i.e. dashlights, headlights etc.? The issue is, is that it will do it with the rear defrost on and with hellas off, so it shouldnt dim then since it is all stock options no?
 

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Discussion Starter · #11 ·
Can anyone help locate the engine ground strap for me, that's the only thing I haven't checked yet
 

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For most engines it's near the firewall. Since all the electronics ground to the cabin, usually, so does the block.

~psguardian
 
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