I have a 2005 Blazer that has started having some electrical issues.

I first noticed at night when I turned on the interior light that the light was slightly pulsing (just dimming a bit) rapidly. It has gotten progressively worse. This occurs at idle and on the highway, with nothing on or with everything on.

The pulsing is at all RPM's. It just changes the frequency. It is not dimming from music. It is rapid like you were looking at helicopter blades spinning.

Once I noticed the light issue, I started fiddling with things like the fan speed and rear defroster. The alternator seems to have lost a lot of its ability as well. I tested the voltage at the battery and every little thing I turn on drops the voltage significantly. With the fan on, the rear defrost and the interior lights on it drops well below 13 volts while running.

I have completely disconnected the stereo, which made no difference.

I took the truck to the dealer and was told that this is completely normal. They even admitted to seeing the rapid pulse of the interior lights during the day.

Anyone have any idea what is going on with the alternator?

Thanks for any help.
Brad

Sorry for the long post, but I wanted to add one more thing.

While sitting at idle, all you have to do is turn on the rear defrost or roll down a power window and the voltmeter gauge drops down immediatley to just over 12. (it's a factory gauge so the incriments are not exact) Any one thing will drop it fast. Add more accesories and it buries the needle.

I've seen this before in alot of the Montanna vans,you might want to have your charging system checked. Possibly one of the diodes in the Alt going bad.

sounds like either a bad voltage regulator or the alternator needs a rebuild

have the alternator load tested .... most auto electrical shops should be able to do this

Yep, something ain't right with that alternator.

Assuming the truck is still under warranty since it's an '05, take it to the dealer and start bitchin'. They should have to replace that alternator with a good one.

I have taken it to the dealer and had it load tested. They said that the diodes check out and that the alternator is fine.

They produced a bulletin from GM saying that it is perfectly acceptable to have the voltage drop way down at idle, if any accessories are on, including the headlights. (mine does it at all RPM's)

The mechanic admitted to seeing the rapid pulse in the interior lights but said that he can only do what he is told.

The service manager sat in the truck for 2 seconds and said that is normal.

I said pulsing interior lights and 12 point something volts out of an alternator is not normal.

Finally I was told that I have to have some sort of failure for them to do anthying else.

I was told by as local shop that it is almost like A/C is getting through the thing??? Any chance of this ? Any chance of this causing damage before I have a "failure"?

Looks like I am going to have to start looking at a new alternator. I was expecting to have to replace mine once the stereo was all installed. I didn't expect to need one 6 months after I bought this truck.

Any other ideas?
Thanks for the help.
Brad

It won't be the alt.

Ask anyone that has been working on cars, Manufactures down grade aver aspec of the car to save money. This means they use smaller gauge wire, you see they use smaller gauge wire BUT the Load from power windows or Rear Defrost has not decreased. Most windows take about 10-15 amps per window depending how old the system is. The issue is the wiring can not handle the current draw. Turn on your int lights and hit the brakes, the lights will flicker also.

In the newer car you will start to see 24volt systems. They will increase the voltage to combat the amp draw. I think Toyota and GM have been working on a 24-48 volt car.

You could try upgrading the ground strap from your Battery to the Engine Block and Body pannel as well as the power line from the alt to the Battery.

[ November 16, 2005, 10:57 AM: Message edited by: Claudio Piccolo ]

__________________
Claudio Piccolo

try another dealer or maybe a couple. ask on the blazer forum.
sometimes i do not understand it but some dealers who u got the car from just wont be willing to help??? This is the case for me as well, the dealer we bought 2 grand cherokees and 1 dodge ram hemi truck wont help me out with anything. yet the chrysler dealer down the street whom i bought nothing from is always happy to perform any kind of service or warranty work which is deemed questionable and debatable at the dealer where we bought 3 cars.....this totally beats me.

__________________
Team Fear Of Bass

2006 & 07 - Canadian Street A & B Record Holders
2007 Street A - 155.2 db's
2007 Street C - 154.8 db's
2007 CSPL Amature 1 Champion - 150.8 db's

Blazers commonly have alternators fail even 05's!

Yes, all new cars are supposed to be 36 volt battery / 42 volt (they're not gonna bother stopping at 24) charging systems by 2010 I think... Might be 2015.

Anyway, ya, you can try trouble shooting things yourself as implied above... Start adding the "Big 3" and see if that helps.

If not, I'd pull that cabling back out and start writin' bitch letters - not that it'll necessary get you any results, but it'll make you feel better.

Then, when you're ready to add audio to that baby, yep, be looking at an alternator upgrade too.

__________________

95 Astro Cargo Van
KW KDC-X979
DVD, XBox
RF Punch 55.2 - Orion Cobalt 5 1/4's
ALP V12 - KW KFCX698 6x9's
CLAR APX400.4 - KFC-X698
(2)Orion 1200D - (2)DC Audio Level III 12's
146.4 termlab no wall.