Also posted on Planet Isuzu...

Brake light and battery light come on after starting the car (1995.5 Rodeo S, 3.2L V6, 4x4 with manual tranny).

The lights clear immediatly after reving the motor above 2K rpm and don't come back on while driving at all. The volts seem to be in the normal range too. Haven't really paid attention to it that much though.

I think this started after going to the car wash. What I first noted was that the AC blower fan wouldn't come on right away after starting (the battery light didn't stay on. Now the other night the brake and battery light stayed on after starting and instantly turned off after reving the motor up.

Anyone seen this before? Possible loose or corroded wires on the alternator maybe? The last time my alternator went out, about 2 years ago, it just died suddenly with no warning at all as I was towing my tent trailer home from a camping trip. Limped back into town running on the power in the batteries (my tent trailer battery is wired to charge when the trailer lights are plugged in). I immediatly killed all hights, stereo, fan blower, etc and one by one another dash warning light would come on as the batteries lost juice.

Anyway, I had my trusted local independent mechanic replace the alternator last time, and I seem to recall he had an issue with finding the correct replacement... 3 wires versus 4 or square plug versus round or something like that. Online parts vendors seem to show two different Hitatchi alternators also.

I'm hoping that it is just a corroded contact... but my luck its internal to the alternator / voltage regulator...

What nobody? <img src="/forums/images/graemlins/smile.gif" alt="" />

Last night I confirmed that the belt was tight, and tightened it up a tad more. I also confirmed that the wire plug (round) in the back is tight, but I couldn't really reach in well enough to unplug and replug it in to check the contacts.

Same behavior as before, engine starts, battery light and brake light stay on, voltmeter reads about 11 volts, which makes sense with the ignition / fuel pump / ECU drawing from the battery. Blip the throttle and rev it and the warning lights instantly pop off, the volts come up between 13 - 14V and the warning lights stay off.

Anyone lived with this condition? Or just go and fix it right away?

Thanks!

well what about the condition of the battery?

how old is it and its connections?

what is the voltage meter (not the one that came with the vehicle, but a multimeter) reading while starting the engine with lights and stuff on?

then do that same test a second time

that should give a clue as to to battery.

If you are reading 11V anytime the engine is running, then you have a charging problem. The ECU, ignition and pump do not draw that much juice. I don't think the batteries are your issue.

It sounds like there is something wonky with your regulator. Tightening the belt and wiggling the plug are not diagnostic activities. You need to either take the vehicle to a place that can test your charging system in situ or pull the alternator and take it to an electrical shop to be tested.

Good Luck,
Michael

OK, Problem Solved!

The battery is practically brand new. 13.2V with nothing drawing any current. Belts tight, no corrosion on the connectors, connectors nice and tight, charging system relay is good, fuses and breakers all OK.

After start, volts as read on both dashboard voltmeter and on my DMM was 12.1V with the motor running at idle.... NO CHARGING appeared to be going on from the alternator, and the brake light and alternater warning light both illuminated on the dash.

Reved the motor beyond 2K RPM and suddenly the dash lights go out and the volts jump up to 14.2 to 14.5V. I figure its the voltage regulator or excitation to the alternator, and that I should be OK.

So I'm with my wife and daughter driving down to San Bernardino from Pismo on Friday for the weekend, and on the highway just before Santa Barbara both the brake light and alternator light come on, the air conditioner fan stops, and the volts drop to 12V. I immediately kill the stereo and headlights (it was about noon). I pull off on the next offramp, stop the car, check the belt, restart the car, rev it, still no charging volts and warning light stays illuminated. Dead alternator.

So I drive to a garage on battery power, he puts on a load tester and confirms what I said, dead alternator, and he can't get the part until 4:00 pm.

So wife, daughter and I walk from the shop down to a restaurant to eat lunch and wait. After lunch I get a wild hair and we walk down to a Nissan dealership just down the road....

.... and after a walkthrough of what they had on the lot, they went and picked up my Rodeo and I traded it in on an '08 Xterra SE..... Problem Solved <img src="/forums/images/graemlins/smile.gif" alt="" /> It was a good 13 year, 178K mile run, but I simply can't afford to be without reliable transport over the next year. So all's well.

So let this be a lesson: Don't ignore those warning lights. They come on for a reason. Mine gave me about a week of advanced notice of emminent failure, but I hardly drove it during that time.