Hey All,

Yesterday I replaced a failed fuel injector on cyl. 4 and got it all buttoned up and ran it for about 30-40 minutes to do normal operation check and everything was perfect. Even came back and restarted after a cooldown and all good.

This afternoon I tried to start it and it is electrically dead. I checked the battery and it read .02 V! (I also put in a brand new battery yesterday.)
Yesterday there were no warning lights indicative of a charging problem the entire time it was running. I put my meter on the 100A main fuse and it was good. I'm putting the battery on the charger now and it should be charged up by tomorrow morning.

Any ideas on how this could go from perfect running to being totally dead after 12 hours and no warning?

Many thanks!

Easy. (yeah, easy to say from here) Easy, something's on. Something significant.

Testing. Also easy from here. Make sure everything is turned off. Especially the lights as they're the most likely suspect. Parking, interior, headlights, glove compartment, trunk, +++, you get the picture. I'm guessing even if the charging system was faulty, you wouldn't be down to dead-dead today. An aftermarket stereo. They are notorious for bad wiring/phantom draws/failures, all sorts of problems. Especially since they require unswitched (always on) power along with switched power. Aftermarket alarm systems.

If all that fails, pull a battery cable. There will always be some draw, and a draw will generate a spark, but a tiny one or a little bit bigger? Even a cheap DMM will usually measure at least 6 if not 10 amps. Make sure it's on the right scale and the leads are in the right place, they generally need to be different than normal. What does it read? If it's more than 30 or so milliamps, it says you have a problem. If it went dead in 12 hours I'm guessing it's over a full amp. At worst, start pulling fuses and see when the draw goes away.

The first two fuses to draw-check are 15A #4 in the cabin fusebox (audio/nav, which you probably already know about) and 7.5A #65 in the underhood Fuse&Relay Box. The latter is for the alternator fields and will suck about an amp if there's a blown diode in the alternator.

Hey Guys-

Thanks for your thoughtful replies. I'm kind of mystified. Put the charged battery back in and while running I see that the voltage is staying around 13.8V and with headlamps on it drops to 13.5. Went though all the likely culprit fuses and all are intact. I have no aftermarket electronic modifications and nothing was left on (I even have the headlamps set to manual off all the time).
RE: Blown diode - I assume alternator output would go to zero if that occurs and the 7.5 amp fuse would be open?

Not to zero, but the output would fall off seriously. The diodes rectify the three AC phases into a single DC source for the battery, so a blown one basically kills output from that phase. Because they cross-couple the AC and DC, how much output is lost depends on whether the diode blows open or short. An open one will simply cause low output, a shorted one will cause both low output and a draw. Shorted or open field coils will have much the same effect.

Allright, tested for parasitic draw and got 53ma. Is that within tolerance? Went though every fuse in engine bay and cabin and current draw didn't change. I drive this car pretty infrequently. In a year I put on less than 600 miles so I wonder if we're talking about a switch contact or relay that's corroded.
Thanks again!

That's a little high but not enough to make a battery go dead overnight, more like over a week. I'm wondering if maybe your battery has a bad post. It will have lost substantial capacity anyway after recovering from a total discharge, chances are it's got some serious sulfate. So a new one won't be a bad idea before you go chasing anything else.

Geez, I'm embarrassed - had the VM on the wrong scale- actually have 5.5A draw happening. Should reiterate that I am using a new battery that reads 12.4v. I pulled fuses again and this time when I removed the stop lamp fuse, the draw went down to 1.5A (door lamp switch active I suppose). Does that mean the switch under the brake pedal is broken?

Thanks!

Figured out what went wrong - the little bumper that pushes the brake pedal switch in when brake is released had broken - found it under the floor mat. Another thing to expect in a 24 year old vehicle I guess!

Thanks!

Ah, the old brake switch bumper trick. Don't feel bad, all of us have fallen for that one at one time or another. It's a classic.

VStar650CL wrote: ↑

Sat Apr 22, 2023 2:59 pm

Ah, the old brake switch bumper trick. Don't feel bad, all of us have fallen for that one at one time or another. It's a classic.

Yeah, since my repair work was during the day of course I didn't see the lights that were on. The other dumb assumption I made was to try to associate it with the repair work I'd done the previous day.
Thanks!

MisterH wrote: ↑

Sat Apr 22, 2023 3:13 pm

Yeah, since my repair work was during the day of course I didn't see the lights that were on. The other dumb assumption I made was to try to associate it with the repair work I'd done the previous day.
Thanks!

No, that's always the smart place to start looking. On the other hand, I'm so used to European cars which switch the brake lights with the ignition I'd have never looked there.