Still Wondering....

[richp]

Hi,

A couple of months ago I posted about a dead battery situation, in which there was no apparent reason for the battery going down over a week or so of the truck sitting unused. The dealer found nothing and the truck was OK until last week.

It happened again last week after the truck had sat for only 3-4 days unused. My dealer here at home let it sit for another three days before working on it, and found nothing wrong.

Anyone have any ideas about what might be causing an intermittent drain like this? It's going to ruin the batteries if it keeps up, not to mention the trouble I'll have if I'm off rafting for a week and come back to some remote boat ramp and it won't start.

Thanks for any further help.

[Mark Rinker]

How old are the batteries? If you can't find a parasitic drain, then it may simply be one failing internally.

...or it something that YOU are doing differently, every once in a blue moon - like the cell phone charger, GPS, dome light, cargo light.

...a bad brake light switch? My Camaro flattened the battery a couple times until I figured this one out.

Hmmmmm....Global Warming? :D

[richp]

Hi Mark,

Thanks for the reply.

The truck and batteries are a year old this month. But if I keep deep cycling them this way, they won't be long for the world, which is why I'm trying to nip this in the bud.

I don't keep anything with an auxiliary draw plugged in, and have checked to be sure all the lights are off at night.

After I got it back from the dealer I let it sit for 4 days of single digit temps. It started with about a 5 second delay for the glow plugs and another 2-3 seconds of cranking, so when they're up, they're up. On the other hand, the serious drawdown that caused me to take it to the dealer this time was not in temps anywhere near that cold. Go figure....

Wouldn't a stuck brake lite switch illuminate the rear lights?

Thanks.

[Mark Rinker]

Can you warrantee out the pair - to eliminate a bad cell in one or both batteries?

[richp]

Hi Mark,

I've already been thinking that if this happens again, I'm going to argue that they should replace the batteries simply because the deep cycling is killing them. But I believe I should have at least one more instance before I try that.

Thanks.

[MacDR50]

I am not an automotive electrical expert but have done a bit of troubleshooting this same issue on cars, motor homes and most recently on my own trailer.

Have someone who knows how to use an ammeter measure the current draw when the truck is not running and the key is in the off position. If you get a significant positive reading you have a draw on the batteries which needs to be located. (Note that the trucks ECM etc may draw a small amount (mA) to maintain error codes. I would be looking for a draw greater than 1.5 amps. Most small automotive bulbs draw between 0.9 and 2 amps. Other circuits such as the anti-theft for the radio may also befuddle your search.)

Pulling fuses one at a time can help you identify the offending circuit(s). My experience has shown that broken interrupt switches such as the one for the glove compartment light are often the culprit. After market accessories are also sometimes the problem as they may not be getting their power from a circuit that is tied to the ignition switch's control. An ammeter will tell if they are still drawing power after they and the truck are turned off. For example, are your brake controller status lights still on when you shut off the ignition?

I wish you luck. The last time I did this I found an offending trunk light switch that had been broken/dislodged and was no longer shutting off the light. Since this was on the courtesy lights circuit I spent a lot of time tracking down the problem on that curcuit. A darken garage finally helped pinpoint the switch.