volt meter and battery light

tennisshoes
43,185

Asked by tennisshoes Mar 05, 2013 at 10:27 PM about the 1996 Isuzu Trooper 4 Dr Limited 4WD SUV

Question type: Maintenance & Repair

Volt meter reads normal, about 14 volts at idle and battery light is off, if you accelerate like climbing a slight hill or passing on the freeway the voltmeter drops to just under 12 volts and the battery light comes on, if driving at night you notice the lights also dim, back off the gas and everything goes back to normal. I was told it was the alternator so I replaced it and all of the belts, same problem, took out the new alternator and had it tested, and it checks out very good, the guy told me that this is a ECM controlled alternator and that might be the problem.  I put the alternator back in and checked wiring up the side and to the main plug in the engine bay, didn't find any problem there.  Anybody got any ideas?

9 Answers

judge_roy
Not Active

the voltage regulator is part of the alternator...maybe you got a dud. It's not unheard of.

7jimmy7
14,645

I think the troopers had a blue relay or something tied to the air cond. relay and one is for charge , look at relay box

1 out of 1 people think this is helpful.
judge_roy
Not Active

..wow kinda guru-ey, just like the genie...

King Hostile
75

Your ignition modules(units the plug wire come from) could be failing and forcing the battery to supply the missing voltage during acceleration, or under load.

tenspeed
69,615

First thing that came to my mind is a broken wire or bad electrical connection. When the engine is under load, it moves in the mounts, pulling on a wire and the circuit opens. - Give the wiring a close look before throwing more alternators and ECU's at it.

2 out of 2 people think this is helpful.
Best Answer
1Delone
60

I had a similar sounding problem once. What I found was the engine ground strap was broken and as the driving torque of the engine increased like climbing a hill or accelerating, the engine would lift just enough to loose the ground. This sounds impossible but ground the engine to the frame & engine to the battery and see what happens.

1 out of 1 people think this is helpful.
tennisshoes
43,185

Thanks for everyone that responded to my problem. The problem was the ECM, for some unknown reason it would put the alternator into economy mode during acceleration. ECM replaced problem is gone. Happy Trails

5 out of 5 people think this is helpful.
judge_roy
Not Active

please click 'mark helpful' for those of us who you thought were helpful. I gave you ten points....just 'cause I can~

1 out of 1 people think this is helpful.
Spicythai2000
10

Since the alternator is control by the ECM find out which wire from the alternator go to the ECM. Cut that wire so the ECM does not control the alternator anymore. My friend is a master mechanic and did that to his customer car. No more battery light and everything is ok

1 out of 1 people think this is helpful.

Your Answer

Add photo

Related Questions

Trooper
Looking for a Used Trooper in your area?
CarGurus has 137 nationwide Trooper listings starting at $2,495.
ZIP:

Search Isuzu Trooper Questions

Isuzu Trooper Experts

#1 N8dogg
N8dogg
Reputation 310
#2 tennisshoes
tennisshoes
Reputation 200
#3 DerekW85
DerekW85
Reputation 110
View All

Related Models For Sale

Used Toyota 4Runner"
247 Great Deals out of 11,914 listings starting at $1,992
Used Isuzu Rodeo"
9 Great Deals out of 353 listings starting at $1,850
Used Mitsubishi Montero Sport"
6 Great Deals out of 368 listings starting at $1,995
Used Nissan Pathfinder"
207 Great Deals out of 16,728 listings starting at $1,900
Used Mitsubishi Montero"
5 Great Deals out of 144 listings starting at $3,300
Used Toyota Land Cruiser"
18 Great Deals out of 727 listings starting at $5,800
Used Jeep Grand Cherokee"
833 Great Deals out of 59,444 listings starting at $1,150
Used Jeep Cherokee"
156 Great Deals out of 49,528 listings starting at $1,800
Used Toyota RAV4"
657 Great Deals out of 37,521 listings starting at $1,995
Used Honda CR-V"
652 Great Deals out of 50,908 listings starting at $1,499
Used Jeep Wrangler"
348 Great Deals out of 42,076 listings starting at $1,800