Battery light


Old 01-08-08, 08:46 AM
Thread Starter
Join Date: Jan 2008
Posts: 3
Battery light

Could anyone tell me what would be causing my battery light to glow all the time? It's not bright like a warning light should be but glows enough that my son in the back seat noticed it one night. I have a 2005 Trailblazer and have had two new alternators and a new battery since September.
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Old 01-08-08, 03:01 PM
Join Date: Jan 2007
Location: Central Indiana
Posts: 389
At startup, the current flowing through the battery light to the alternator regulator is what gives the voltage regulator the juice to start the alternator generating. There is a rectifier/diode in the circuit that prevents current from flowing backwards when the engine is stopped and ignition off. Your battery light glowing dimly would indicate that the voltage regulator is still drawing some current through this circuit. Generally, once the alternator starts generating, the voltage on the alternator side is higher than the battery and no current would flow after startup. Perhaps the dim glow is indicative of a poor connection at the alternator - just a guess. The battery light will glow brightly in the case of a regulator failure.

I had a dimly lit battery light on my '65 Mustang and put it to good use. Whenever I got pulled over for speeding, I would show the light to the cop and tell him that I was hurrying home before my car died. Got me off the hook several times!
Old 01-08-08, 06:12 PM
Join Date: Feb 2005
Posts: 579
Usually when the battery light is illuminated on a GM vehicle while it is running, indicates the alternator is bad. Could be running below specs amp wise, or have a fried diode.

But go ahead and check all the connections to verify proper tightness.
Old 01-09-08, 06:30 AM
Thread Starter
Join Date: Jan 2008
Posts: 3
Thanks for your help! Formula, I never would have thought of using it if I got stopped for speeding, but now I'll keep it in mind, lol! I got my hubby to hook up the battery charger and check out my battery and it said that it was only charged to 60%. My local GM service centre keeps saying that I'm imagining things so I have an appointment to take it to another one on Friday. I took a pic of the light with my cell phone today so that can't say that I'm just imagining it! It's funny...both times I've had my alternator replaced, there was no indication that something was wrong until one day my car wouldn't even turn over!

Another question...does anyone know if a satellite radio would drain my battery? When I got my new battery they told me it was my satellite radio that killed the other one so I've been careful to remember to unplug it every night but the radio dealer said there is no way it uses enough power to drain the battery overnight.
Old 01-09-08, 08:45 PM
Join Date: Sep 2007
Location: wisconsin
Posts: 73
well we had one in shop same exact problem

to make a long story short after checking charging voltage with the tech 2 and looking at the cluster data it was not requesting the light on but it was on dim

the fix for that one was a new cluster

Old 01-15-08, 02:22 PM
Thread Starter
Join Date: Jan 2008
Posts: 3
Well, apparently I'm either delusional or senile (and I'm only 35 lol!). They said that there is nothing wrong with my car (after driving 1 hour to get there) same as they have said the last 2 times I've taken it there. It still happening too! My husband hooked it up to the charger to check it 3 times since then and it's always between 65% and 70%. He charges it up to 100% and the next morning it's back down again and the battry light is on again. The "fixed operations manager" called today to see if we can find out what's going on...he was MUCH nicer then the condescending service manager! Between family and business vehicles we own 4 GMs but I doubt they will be replaced with another GM when the time comes!

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