Low voltage on start-up - slow start

[islandgirl62]

Again- Mods please put this where it needs to be (can't post a new thread anywhere but here.)

Background: On our 2006 Duramax: First had problems with low voltage, especially on start-up. Took it in and the shop replaced the alternator. About 9 months later, started having trouble with dead batteries periodically, especially if the truck was not started for 2 days. Put 2 new batteries in (about 1-1/2 years ago now). That helped for awhile. Started in with the periodic dead batteries again about 6 months ago. Last week we replaced the alternator again. Still showing lower voltage when we start the truck (somewhere around 11.5 v or so) Takes awhile for it to show 14 v charging. NO warning lights or messages regarding the charging system. Truck seems to turn over slower than it used to. Have been reading some on the internet on this topic.....sounds like this might be a "normal" thing with the changes made to alternators around 2005. At the autoparts store, the batteries test out good. Don't have a lot of confidence in it here lately...afraid I might get stranded somewhere with dead batteries.

Do you think there is something wrong? IS the lower voltage at start-up normal? If we're going dead in 2 days, there must be some sort of draw on the system, right? Any suggestions if this is thought to be a problem? One note, from some of the threads I've read here and on other places - heard mention of glow plug problems causing this.......We are NOT in a very cold climate (west Texas right now) and it happens no matter what the temp....BUT we do have one glow plug that throws a code every time we cold start (cold start as in engine cold, not outside temp cold). Could this be the source of the low voltage and/or the dead batteries?

Any help/suggestions would be greatly appreciated. Duramax Diesels Forum is my primary source of answers to my questions on our trucks! Y'all are THE BESTEST!!! :thumb:

 

[TeaBagger2006]

Glow plugs Draw juice on startup . What's the temperature right now?

 

[islandgirl62]

The temps right now have been in the 40-50's at night. A few nights of low 30's, but this is happening even when it's in the 60's or 70's at night.

 

[CancerPipe]

When its cold enough mine is how voltage until the intake heater, glow plugs ect are done cycling. Truck turns over a little slower, but always starts.

 

[islandgirl62]

we always wait for the glow plugs before we start it....it still seems "harder" starting than it used to. Just hate that "click click click" of dead batteries and that is a worry if the truck hasn't been started for a day. (like if we just got home with the truck a little while ago, and if we don't start it all day tomorrow, wait until Monday, it might start, might not)

 

[JoshH]

What kind of batteries did you put in it? It sound like they need to be replaced again.

 

[nuffsaid]

Draining automotive batteries down to dead several times can kill them. What kind of batteries do you have? Have seen a lot of problems with Exide made batteries. Batteries are load tested to about 1/2 of cold cranking amps for 15 seconds, so if the battery is rated at 700 cca, test needs to produce 350 amps for 15 seconds without the battery dropping below around 7.5 volts. On a diesel, batteries must be testing individually. My guess is that your batteries are weak. Typically, after starting, the glow plugs and intake heater can remain on for quite a while causing the voltage to remain low due to the electical drain. Before spending a great deal of time trying to find a phantom electrical drain, rule out the simple, the batteries.

 

[islandgirl62]

The batteries are......dang, can't remember - the yellow/gold top from Autozone. We have had them tested, but while still in the truck and hooked up as normal. Do we need to disconnect them and then test? I'll definitely give that a try. Would rather spend the $ on new batteries if that fixes the issue. Finding a draw can be a royal pain!
Thank you for the replies! I LOVE the Duramax Diesel forum!! :happydance::happydance:

 

[DAVe3283]

Let us know how the individual batteries test. If they are good, and it goes dead in 2 days, you have a serious drain.

For a total battery capacity of only 85 Amp-Hours, that is a 3.5 amp drain. Plus, your truck probably has more than 85 amp hours of capacity, which means more than a 3.5 amp draw. Your truck should draw less than 0.2 amps when sitting, which would cause it to go dead in well over 2 weeks.

 

[mtl_dmax]

Let us know how the individual batteries test. If they are good, and it goes dead in 2 days, you have a serious drain.

For a total battery capacity of only 85 Amp-Hours, that is a 3.5 amp drain. Plus, your truck probably has more than 85 amp hours of capacity, which means more than a 3.5 amp draw. Your truck should draw less than 0.2 amps when sitting, which would cause it to go dead in well over 2 weeks.

X2

I'd use a multimeter and check the amperage draw (ie probes in between battery and cable) on your batteries with everything off.
If you find the current drain is excessive, then you'll need to track down the culprit to solve your issue.

 

[bondurch]

Battery cable corrosion

I had the same issue with my truck and found that the wire had corroded at the battery connection. If you can remove the battery terminal from the battery then look at the wire connected to the battery terminal you will probably see corrosion. Clean with baking soda and water and a wire brush. Do this on every battery connection.