View Full Version : Battery idle woes any ideas?
12-15-2011, 08:52 PM
I noticed my lights were dimming while I was idleing at traffic lights and I left my truck running outside the other day and I came out to find my truck no longer running and my battery dead :( after a boost I drove around for a while the battery charged back up and every thing seemed fine. I was curious what had happened so I started up the truck and let it Idle till it was warm and the rpm slowed to a normal idle. I hooked up my multimeter the battery terminals and watched as the voltage slowly dropped started at 13.6 volts and slowly dropped to 11.98. When I reved up the engine it would climb back up so it seems that where the truck was idleing at was not spinning the alternater fast enough to charge the battery so I adjusted the idle up untill the voltage was no longer dropping I know the rpm should be 800 +/- 50 but I can't be sure what my rpm is without a tack. So I guess my question would be is it going to hurt anything to have my truck idle a little high? I took her for a drive and sure enough no more headlight dimming! So it seems like that could have been the reason why I came out to a dead truck the battery got run down because the truck was'nt idling high enough to provide the battery a charge.
Any thoughts anyone?
12-16-2011, 12:18 AM
battery and alternator have kind of a suicide pact with each other..a bad one of either can kill the other.many times with an older vehicle your problem could just be a simple improvement in grounding of the engine and battery. The stock ground strap can get pretty crummy after 20 years..adding a thick cable (like the ones used in high powered car stereo amps) from the battery - to the alternator at one of its mounting bolts,and another from the - battery to the frame will ensure you have sufficient ground..also check you + cables as well...loose battery clamps can cause poor charging...regarding idle..I can't see how a tiny increase in idle will affect anything other than an emission test and use a bit more fuel...if you're talking about 100 rpm increase or so it shouldn't be a big deal ..grab yourself a tach. since you have a 4 cyl. you won't have the same restrictions in finding one compatible with your truck that we 3 cyl. guys have ...it's poss. the idle was low and you are just bringing it up to where it should be
12-16-2011, 11:20 PM
Yea, I have the same problem, but mine is self-induced, having messed with the pulley sizes. I get about the same numbers as you, and can kill the engine after about half an hour at idle, using pwr windows, ac etc.
For me, I didn't think that the pulley size would make that much of a differance, but it did. 11.5V @ 950RPM and 14V@ 3500RPM.
For you, I would suspect that your carbon brushes are at the end of their service life, and are experiencing "hang-up". You could install a larger capacity Ah battery, or just remove it and have it rebuilt; new brushes. Any alternator shop in your area should be able to do this.
Or, just leave it at the higher RPM, if you're OK with that but, either way, it will fail completely in the next 100 OHr. :(
12-17-2011, 11:37 AM
Yikes! I better start looking into pricing for re building the alternator and I'm going to shop around for a battery that will fit in the tiny battery box on my sambar. "failing completely" does not sound like a good option for me. Thanks for the advice guys I am loving this forum! And owning a kei truck!
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