Any auto mechanics?

[CUBuffs]

Can anyone give me an idea why an Isuzu Rodeo would have trouble maintaining a charge? It has a new battery, connections look good, and the alternator checks out OK but the battery continues to loose power as if the alternator is not working. Any help is appreciated. Thanks.

[prometheus578]

Same as a bike... you have a short or power drain somewhere. bad switch?... any lights stay on that aren't suppose to? Trunk... under hood if you have one there? Put a voltmeter across the battery... see what it reads. Then start pullin' fuses till you find the one that makes the battery reading go up. that's the circuit that's drawing off the power. Two Notes: If you have an electric clock, or the radio stays illuminated, that'll draw off power, but not much. Be advised... that when you're checking fuses, you may have the door open, and that little light is also draining juice while you're checking. Take out the bulbs or disconnect the door switch first.

[Geezer]

It's also possible that the alternator is only partially working. Perhaps one circuit in the stator is open or there is a bad diode in the rectifier.

Geezer

[Czekus21]

Fire up the cage. Disconnect the neg. cable from the battery. It should still run. If it doesn't, I'd be looking at the Alt. Thing about Isuzu's ( both Rodeo and Trooper ) The motors are made by GM as well as the trani's. They did have a problem with grounding. ( mainly the electronic controled 5 speed automatics ). Have you had any trouble with it shifting from gear to gear? If so, this is an indication of a grounding problem. Does the starter sound " not right "? mabee like it's kinda draggin ? If so, you may have a starter pulling too many amps and thus putting XSive load on the battery. I would try the neg. cable thing first.
Also should point out that just because it's new in the box, Doesn't meen that the battery it good. If the alt checks out and grounding is good, amp draw on the starter is good Get a hold of a battery electrolite tester ( duo check ) . How are your battery cables ?
There's alot of stuff that could cauz the problems your having. But this stuff is what I'd be checking first. Kinda help narrow it down.

[e.z.nightrider]

Sometimes it's the simple things, is the belt loose and slipping on the alternator (doesn't have to slip enough to squeel. Don't ask how I know.

Ed Z

[Dragonrider]

(snip)
Fire up the cage. Disconnect the neg. cable from the battery. It should still run. If it doesn't....
(endsnip)

Uh...NO...don't do this. Most modern voltage regulators/alternator combinations will fry the regulator when the load (battery) is suddenly removed. The field voltage goes up so fast the diodes go "sproing" before it can unload.

Check the voltage at the battery with the car not running. Fully charged battery should be around 13 volts (13.3). Start the car. Check the voltage again. You should get around 14v or so if the alternator is charging. If it doesn't change or goes down, you are not charging. Bad regulator, bad alternator, slipping belt, or perhaps a blown fusible link in the charging system (some are right off the alternator, some are near the battery, some are actually in an external fusebox under the hood).

Good luck.

[jetmechmarty]

With the car off, remove the negative battery terminal. Hook up a test light between the battery and the cable. If the light illuminates, there is a draw on the battery. Remove fuses one at a time until the light is extinguished. Once you find the offending circuit, you can start disconnecting components until you find the offender.

[DiverRay]

Try the Alternator
alternator checks out OK but the battery continues to loose power as if the alternator is not working.
The internal regulator may be bad. I had one go out on the beast. It would slowly discharge, and the voltage was only 13.4 at full charge. The Alt. did check out "good" at the local parts store. If you are putting 14.2 to 14.7 volts to the battery, the alt should be good. If you are not putting out that voltage, check for the ground from the Alt case to the engine block, and the engine to the battery. Some alt. are mounted in rubber, and NEED a ground wire.
Ray

[jetmechmarty]

When is it dead?

Does the battery go dead while you are driving? I suspect it isn't. If it goes dead while parked, lots of things are suspect. Use the test light in series method I previously posted if this is the case.

How do you know if the alternator and battery are good? Were they tested outside of the vehicle on the bench or was the charging system tested? I had a Chevrolet that liked to burn out fuse links between the alternator and battery, and a Ford that suffered a corroded splice in the same circuit.

If the battery goes dead overnight it's probably some grounded component that should be an open circuit when the vehicle is off.

[ccogswel]

We have a 96 rodeo that had a similar problem. We had the alternator go out so we bought a new one. But when we did we noticed that when you would shift a gear the blower and the stereo would quit and then come back on after you shifted. We took it back to auto zone they checked it with it on and off the vehicle and everytime it would check out fine. So we just rode it out until it finally went bad. Took it back got a new one now no more trouble. Also another thing you may want to check is the battery cable ends. If they are factory, replace them. One day we went to start it up and it wouldn't turn over. Everything checked out ok. After 2 solid days messing with it and a wiring diagram I was able to hot wire it in the fuse panel under the hood. So I traced the wires and found a bad connection at the battery. Replaced them both and it fired up. Been doing great since except for the lifter noise. Can't get it to go away. Also I forgot who mentioned it but do not unplug the negative cable while its running as it will cause harm like Dragonrider said. Don't know if would do it to a rodeo but I wouldn't want to take a chance.

Uh...NO...don't do this. Most modern voltage regulators/alternator combinations will fry the regulator when the load (battery) is suddenly removed. The field voltage goes up so fast the diodes go "sproing" before it can unload.

I even heard of the computer going out after doing that. Don't know if it would do that on a rodeo but I wouldn't want to take a chance.

[prometheus578]

Same as a bike... My friend, Manual, says don't disconnect the battery while running. (Manuel says one thing, Pedro says another) As for disconnecting the battery and the car should still run, I thought that only applied to Fords(not Chevys) and this was for cars made in the 1960's. I wouldn't care to try it now.