I own a 2005 Rainier. I have been experiencing for some time now a problem with the headlights and the dash lights dimming as I take my foot off of the accelerator. This problem is intermittent and I haven't been able to identify a specific set of conditions that cause this problem to occur. The headlights will sometimes brighten and dim rapidly, sort of a strobe effect. The car has been back to the dealer several times and each time the service manager tells me that this is normal. Friends I have with other GM products do not experience this problem. Has anyone else experienced this problem and if so, how was it resolved.


Thanks, PCFL

Yeah, the dealers say that a lot.


First thing is to clean and tighten your battery terminals. Next, the alternator connections. If you still have the problem, check the ground connections starting with the main negative cable from the battery. Corrosion can set in to any of these, but yours is new enough that it's unlikely unless someone has been working on a given area. It's also possible that the diodes in your alternator are failing, but again, that seems unlikely.

check the output of the alternator, it could just be an overload on the
alternator. Do yo have any stereo systems you installed???

Also may be a wiring issue. I had a 2005 Kia and I had to take it back to the dealership several times because there was a wiring short in the harness because they installed it wrong at the factory. this may be the case with yours as well. If you know anyone at all that is good with electrical stuff on vehicles, you may want to ask them just to give it a once over just to be on the safe side. Other than that, what has already been said.

I have a 1995 park ave with a similar problem, I noticed tonight on the way home. The headlights dimmed and the warning light for the alternator came on for a second or two, then jumped up to about 15 amps. I'm hoping it's a connection problem and not an alternator problem.

Sound advice on the connections/inspections even though posts about a decade old. A working alternator will show though about 14 volts steady at batt. terminals if not attempting to recover battery. A good battery would show maybe 12.5-13 volts (volts these days, not amps anymore) without motor running. Also if battery has dead cells or going bad could affect alternator with dimming phenenomon. With this cold spell and if batt. 5 years old or so on "a wing and prayer".

Used to be a problem with alternator belt slippage but not so much with serpentines if any. Racing, some would have a switch to free spin the alternator or generator running off battery to gain a few horsepower. Can't say how well it worked and sure wouldn't try these times.

Would need a Fluke or should say DC voltmeter, even a cheap one would probably deliver sat results. Also volts is read across batt. terminals and amps in series with positive cable. Could reach 30-40 amp reading on ampere meter with alternator on hi-charge.

Reread tells me alternator is fine...... Battery going bad if charge jumps to 15VDC after lights dimming/flashing. Battery was drained and trying to recharge, my thoughts only.