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2006 chevy trailblazer_ls
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40 Posts
Discussion Starter · #1 · (Edited)
I get a random dim battery light. It shows up randomly and almost always goes away after a couple hours of driving. If I do not drive until the light goes completely away, it will stay on dim when the vehicle is off. I have done no electrical mods to my vehicle. Advance Auto Parts ran the alternator battery test on it with the following results:

Engine off:
.38 A
12.89 V
748 CCA
Engine Start Time 2.24s

Engine on no load:
14.6 V
9.5 A

Engine on with load:
14.8 V
39.5 A

I have no problems with the vehicle starting, running, idling, etc... Just a dim battery light for a day or two every two or three weeks. I run it at least 5 times a week 30 miles highway each way to and from work. It can sit on the weekends for up to 60 hours but that shouldn't be a problem.

Is this something to worry about or just let it go until a real problem shows up?

On a side note which may or may not be related, my key will only turn in the ignition one way. If I put the key in the opposite way, I can not move the key from the off position. Would this be a key hole problem or a key cutting problem?

Also, the serp belt will squeak for 15 seconds on a damp or dewy morning when first started but no other times. Only 51k , no cracks in belt, still feels like it has a lot of grip.
 

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2004 gmc
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26,181 Posts
When the light is on dim, is it significantly dimmer than when it lights up at starting time when all the lamps are being tested?

The instrument cluster, as I understand it from the 2004 shop manual, illuminates that light when it gets a serial message from the PCM or BCM that something's wrong. There should only be ONE brightness of the warning lamp - full on. It's not like the old days where the lamp could indicate how bad the problem is.

Especially if the light's on when the ignition is off, that points to a bad gauge cluster or less likely an ignition switch. At $27 for a new ignition switch, I'd do that just for fun.

The key is definitely a cutting problem. Do you have a spare? If not, don't go ANYWHERE before getting at least one spare. How's the wear on each side of the problem key?

On the belt issue, just swap it. Get a $30 Gatorback. It won't squeak, and then you'll have a spare to carry so you won't be forced to pay $130 at Joe's Garage and Pool Hall at the exit ramp in East Roosterpoot, Texas when it fails on vacation.
 

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2004 chevy trailblazer_lt
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997 Posts
Sounds like you checked out the usual suspects.

I would pull off your belt and check several things: the length of your belt and the idler pulley bearings, tensioner bearings and alternator bearings. Spin them by hand and see if you can feel any grittiness in them. (The slightest bit of grittiness means they should be replaced.)

Also, folks have gotten the wrong size belt from time to time. The EXT version uses a 90.5" belt (with a stock number that ends in 905) while the SWB version requires a 91.5" belt (with a number ending in 915.)

Our belts generally don't squeal much, if at all. If the bearings are fine and the belt is the right length, then it may have gotten some coolant on it at some point in its life. You may want to replace it anyway.

Strangely enough, when bearings go (usually the idler pulley bearing) they go so slowly that we become accustomed to the slight increase in whine and don't even know it ... and then the day we replace it, we are SHOCKED at how quiet the engine suddenly is.
 

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2003 gmc envoy_slt
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Sounds like you checked out the usual suspects.

I would pull off your belt and check several things: the length of your belt and the idler pulley bearings, tensioner bearings and alternator bearings. Spin them by hand and see if you can feel any grittiness in them. (The slightest bit of grittiness means they should be replaced.)

Also, folks have gotten the wrong size belt from time to time. The EXT version uses a 60.5" belt (with a stock number that ends in 605) while the SWB version requires a 61.5" belt (with a number ending in 615.)
Our belts generally don't squeal much, if at all. If the bearings are fine and the belt is the right length, then it may have gotten some coolant on it at some point in its life. You may want to replace it anyway.

Strangely enough, when bearings go (usually the idler pulley bearing) they go so slowly that we become accustomed to the slight increase in whine and don't even know it ... and then the day we replace it, we are SHOCKED at how quiet the engine suddenly is.
Did you mean 90.5" (905) and 91.5" (915)?
 

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Southeast Chapter
2004 buick rainier
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5,864 Posts
i get this every so often also and from what i have read on the site this is one of the first signs that your instrument cluster might be on it's way out. on mine it is very random and just as you described very dimly lit and will stay on after the truck is shut off; i have noticed this problem for over a year and not had a problem because of it. i think that it is just a cluster issue:m2:
 

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2004 chevy trailblazer_ls
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i get this every so often also and from what i have read on the site this is one of the first signs that your instrument cluster might be on it's way out. on mine it is very random and just as you described very dimly lit and will stay on after the truck is shut off; i have noticed this problem for over a year and not had a problem because of it. i think that it is just a cluster issue:m2:
Same exact issue here :yes:
 

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2006 gmc
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My GF has an 04' Envoy SLE. Hers does the same exact thing. No rhyme or reason as to when it comes on. Came on the night she bought it-they replaced the alternator-it was out. 8 months later -I replaced her battery. Has been a few times in between that. You can even see it on very dim when there is no key in the vehicle. May do the cluster thing and see if that does the trick :thumbsup:
 

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2006 chevy trailblazer_ls
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Discussion Starter · #10 · (Edited)
The light is very significantly dimmer than the start up light test. Can barely see that it is on. Someone with bad eyes would not notice it is on.

There are no OBDII error codes. I checked with a code reader.

I have a spare key at my house. I do not carry it with me though. The problem key has more wear on one of the peaks on the top when inserting it the way it can start. I might get another made.

Any idea where to get a gatorback or a model number for a 2006 standard wheel base 4.2L? I like to change my belt every 50k but I think the book said every 100k or 120k. With the tension pulley it makes the change much easier than a pulley on a threaded bolt for tension.
 

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Discussion Starter · #12 ·
Ok, all of a sudden this week the alternator now sounds like one of the crank sirens you see on old movies on cop cars, ambulances, tornado sirens, etc...

Diagnosed it by noticing the sound gets louder with engine rpm not vehicle speed. I know this is not the safest thing to do, but it is the only way I know to diagnose all the items on the serpantine belt. With the engine on, took a large long screwdriver placed the metal end on a solid metal part of the alternator and steering pump, put your ear to the plastic handle on the screwdriver and you hear clearly the sound they are making.

I have never replaced an alternator. I do understand the basics of alternators.

How long do alternators last while sounding like this?
Is it damaging to anything besides the alternator to run it with a whine?
How hard is it to replace an alternator? I have average mechanic skill but I would rather not tear apart an alternator because I think it would be a little advanced for me.
Whats the best place to get a replacement? I normally get parts from NAPA.
Is there any advantage to getting a larger amp model or does that screw with the pulley and serpentine belt sizes?
Is it easier on alternator if it is over sized?
What happens with the amps that the alternator produces but the vehicle does not use or is there some sort of clutch in the alternator?

Thank you for any information you can provide.
 

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2004 gmc
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What happens with the amps that the alternator produces but the vehicle does not use ...
I'll let others chime in on the other questions, but on this one I have some (40 years) electronics background.

The amp rating of an alternator or a fuse is the MAX it can supply if asked to. It can happily live delivering a much lower capacity. It's exactly the same as the water supply to your house. The street piping can carry a LOT more water than you are using at any one time, and if your faucets are off, nothing flows down the final supply pipe through your meter to the house. It's just POTENTIAL water flow and only open faucets turn it into ACTUAL water flow.

The PRESSURE in the pipes is the VOLTAGE on the system.

Gallons per hour flow rate is analogous to Amperes (amps) of current flow.

Gallons of water delivered and metered into your bathtub is like Amp-hours of capacity in your battery if the engine is off. Use up too many amp-hours running your radio without the engine, and the battery drains down. And voltage goes lower.

The water analogy to electricity is pretty powerful.
 

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2003 gmc envoy_slt
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:iagree: There is a regulator in the alternator that automatically lets the power through to the battery when needed. Check Parts4Chevys.com or any of the local parts stores for alternator prices.:m2:
 

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Also dim battery light

I also have an intermittent dim battery light that stays on after the ignition is off. I noticed it on extremely humid days but on the dry days it disappears.
Now , the oil pressure gauge is pegged when off and the tachometer gauge indicates 3000 RPM too high. I still have the extended warranty and it is going to dealership this afternoon for new instrument cluster. It appears all my problems may get resolved with a new cluster.
The dim battery light was so intermittent that the dealership never could see the problem. Now with the gauges being bad, they have no problem replacing the cluster.
 

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2008 chevy trailblazer_ls
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Reviving an old thread. My 08 Trailblazer does this same thing. We replaced the alternator, inside pulley part (bearings?), belt, battery (connections are good). When the battery light displays, it is randomly dim to bright but not fully illuminated. The gauge fluctuates between 13-15 and corresponds with how dim/bright the light is. I would definitely suspect the cluster, but when this happens, the interior lights and headlights pulse. Unless that's just a coincidence and a completely separate problem.
 
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