'03 Sierra - All Lights Blinking Swiftly

[Turk]

My ole reliable, bought brand new, 2003 GMC Sierra 4x4 with the 5.3L that I rarely drive anymore has all of the lights blinking at a high rate now. Voltage Gauge is reading way high as inconsistent levels.

It has the original Alternator with 183,000 miles on it.

Is the Regulator built into the Alternator on this?

Which brand of Alternator is best to get as I am keeping this Truck a long time...??

Thanks!

 

[meep]

I think the regulator is built into the ECU on this one.

I would DEFINITELY search for bad grounds before spending $. If the ECU is being fed poor (+) or ground, it will "overreact" and juice the alternator.

If you buy an alt, go with nothing but the best. oem or napa gold. most remans, even w/ lifetime warranties, seem to fail annually. been there, done that.

I do not think this is the alternator.

Completely disco the alt and run the truck and see what happens. is the voltage good? measure at the battery.... ~12V? What does the cluster say? same? low (like 9?). what happens if you turn the lights on? does it run rough? poke around some. you are going to have to locate the bad connection.... if that's the cause.

 

[Turk]

The cluster has been varying slowly fron 19V to pinning far above 19v. I have been wondering if the gauge is faulty as it has done it for the past year (2k miles) with NO effects.

This blinking just started this morning...

 

[The_Jeff]

Get a voltage off the battery terminals and read the codes, there might be a clue in there like "unable to control alt field"

 

[Turk]

Originally Posted By: eljefino
Get a voltage off the battery terminals and read the codes, there might be a clue in there like "unable to control alt field"


Truck was sitting for a couple weeks and I hooked up a Schumacher digital battery charger to it a few days ago.

It was reading 12.4v & 60% charged when I went to fully charge it.

I get no codes.

 

[Turk]

I checked all te Alternator connections and they are tight.

Started the Truck and the voltage meter stays at 19v & not pegged. When I shut off the Truck, the rest of the gauges go to "0", but the voltage gauge stays at 19v.

Any ideas??

 

[cchase]

My thoughts are that whatever is going on here is not good. Is there a body control module on these trucks? I'd almost be headed in that direction.

 

[Turk]

Hummm...

Think I'll take it to a place that checks that for free, then do it myself.

That or just change the original Alternator. It is almost 10 years old & 183,000 miles on it.... How much longer do they really last??

 

[cchase]

The thing that concerns me is that the gauge is reading 19 volts when the ignition is off. The alternator should not factor in to that measurement.

If it is the BCM it could do everything you've mentioned, from what I've read anyway. I don't have much experience with vehicles with a BCM.

 

[Turk]

These Cvevy/GMC Clusters have a history of being faulty, so I bet it is.

It's the rapid (subtle) flashing of the exterior & interior lights that I don't know.

 

[yonyon]

Rapid flashing of the lights means the regulator isn't doing it's job. You can confirm this with a voltmeter if you feel the need.

I believe your alternator uses a setup where the regulator is internal to the alternator but has a variable set point commanded (duty cycle type signal) by the PCM. Put an alternator in it, it should stop flashing the lights. It won't fix the broken gauge.

The flashing lights is bad for the bulbs. If the voltage is high it could be bad for most electronic modules (airbag probably excepted.)

 

[Turk]

Originally Posted By: yonyon
Rapid flashing of the lights means the regulator isn't doing it's job. You can confirm this with a voltmeter if you feel the need.

I believe your alternator uses a setup where the regulator is internal to the alternator but has a variable set point commanded (duty cycle type signal) by the PCM. Put an alternator in it, it should stop flashing the lights. It won't fix the broken gauge.

The flashing lights is bad for the bulbs. If the voltage is high it could be bad for most electronic modules (airbag probably excepted.)


Exactly what I was thinking. I'll pick up an Alternator at NAPA, put it in & report back.

Thanks!

 

[Papa Bear]

Originally Posted By: eljefino
Get a voltage off the battery terminals


+1

 

[Turk]

Now the all important follow-up so we all learn...

I bought a NAPA Re-man. Alternator today & put it in after work. Easy.

Problem fixed -- no more blinking lights!