Engine Runs but Battery Dies (1 Viewer)

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Are you sure this is t a different issue? What did the battery measure when you got home?

If you can kill it by touching the brakes, perhaps your brake booster is shot. That could cause a huge vacuum loss, which would cause it to die... but, should be a slightly different death.

Another thought... check the brake light circuit and make sure it's not shorting out.
 
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The saga continues:
I got it running last night and drove it almost out of the neighborhood. I had to apply the brakes at the exit of the neighborhood and it died as soon as I did. I got it started again using my jump pack and touched the brakes as I shifted into gear. It immediately died. Jumped again. Drove back to the house without using the brakes. I think I'm just going to take it to the local cruiser shop. Electrical stuff frustrates me.
Are you still getting 7V at the battery running or not?

Sounds like every time the brake lights come on the voltage drops far enough the ignition stops working.

Do you have a battery charger, see if the battery will start the engine after charging overnight? Or, if you're jumpstarting from another car, leave it connected and running for 20-30 minutes before trying to start it.

Regardless of the battery, if it's not at least 13V running (rev it up a bit watching the meter), either the alternator or the wiring to it has a problem.
 

Ocho77

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The saga continues:
I got it running last night and drove it almost out of the neighborhood. I had to apply the brakes at the exit of the neighborhood and it died as soon as I did. I got it started again using my jump pack and touched the brakes as I shifted into gear. It immediately died. Jumped again. Drove back to the house without using the brakes. I think I'm just going to take it to the local cruiser shop. Electrical stuff frustrates me.
Man, that sucks. Sorry.
 
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Are you sure this is t a different issue? What did the battery measure when you got home?

If you can kill it by touching the brakes, perhaps your brake booster is shot. That could cause a huge vacuum loss, which would cause it to die... but, should be a slightly different death.

Another thought... check the brake light circuit and make sure it's not shorting out.
Battery measured 5.5V when I got it home. I had the brakes gone through recently by the local cruiser specific shop, and it's definitely a no spark death. Brake light circuit could certainly be an issue, but I think the bigger issue is me not being able to see anything off the alternator.

Are you still getting 7V at the battery running or not?

Sounds like every time the brake lights come on the voltage drops far enough the ignition stops working.

Do you have a battery charger, see if the battery will start the engine after charging overnight? Or, if you're jumpstarting from another car, leave it connected and running for 20-30 minutes before trying to start it.

Regardless of the battery, if it's not at least 13V running (rev it up a bit watching the meter), either the alternator or the wiring to it has a problem.
Not anymore. Last measure was 5.5V. I suspect I could also kill it by turning on the headlights. Maybe I'll try that tonight. No, I don't have a charger anymore. It disappeared around the time I moved from Michigan and Montana. I do have plenty of other vehicles to charge off of though.

Man, that sucks. Sorry.
Yeah, it's been frustrating. Wiring just isn't my thing. I've got it scheduled for a spa day with the local cruiser shop, but that's 19 days out. I'm going try tonight to see if the headlights will kill it as effectively as the brakes. I suspect they will. Then I'll pull the battery and alternator and take them to the local auto parts shop to be tested. The battery might still be under warranty. This could be as simple as a battery with 1 or more bad cells. I suspect the alternator isn't functioning correctly and may have caused issues with the battery. I don't know. I do know that the wiring in the truck is a mess. I plan to do a complete rewire this winter, but I really want to drive the truck a couple times before we get snowed in.
 
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Battery measured 5.5V when I got it home. I had the brakes gone through recently by the local cruiser specific shop, and it's definitely a no spark death. Brake light circuit could certainly be an issue, but I think the bigger issue is me not being able to see anything off the alternator.

Typical car battery is 6 cell lead acid (lead plates submerged in sulfuric acid). Each cell is about 2.1V at normal state. 5.5V is a lot more than 1 cell gone...

And, I'm not suggesting anything's wrong with the brake lamps. It use electricity, by design. Anything using electricity puts a load on the battery which decreases the voltage. If all things were working good, car off, voltmeter on the battery, should be 12.6V, turn the fan and wipers on and that 12.6 will drop (how much depends on the strength of the battery and age of motors, etc...). Brake lights shouldn't take much power, but apparently there's so little available, it's enough to matter.

Lead acid batteries shouldn't be discharged to 5.5V, or really anything under like 11.5 (even that's pretty far), or they start to permanently loose ability to recharge (things happen to those lead plates that cause them not to react with the sulfuric acid). You may be able to recharge the battery a few more times, but really, you need to fix the alternator before replacing the battery or you'll just kill another battery. And assuming it can still be charged enough to start the engine, expect needing a new on in spring (having a low charge in the cold, like Montana winter cold, is really bad for them).

And, you can charge a battery with jumper cables off another running car. Not the most convenient, but in a pinch I've seen it work. You gotta give it some time, watch if with the volt meter.

Your voltmeter has ohms? probably have to move a lead from one socket to another on the meter... Put the two test leads together and make sure it's 0 (or a really small number). Put one lead on the negative battery post and another on the other end of the negative cable (bolted to the frame), should be low, under 100 for sure. Move the test lead from the frame end of the cable to the alternator case (just wherever on the outside of the case), should still be low, under 100. If so, alternator is grounded.

So a "1 wire" alternator (didn't you mention having one?), based on that name, should just have to spin and have one wire to the positive post on the battery (it gets all hidden and muddled and not directly connected through the harness, but, you really should be able to just jump a wire from that one post to the positive battery terminal). I actually get a little lost myself on how alternators and regulators work together and what else is needed, but having researched "1 wire" alternators because I've been considering upgrading (I still have 30 amps...), my understand is all that should be contained in the alternator, it has to be grounded, connected to the positive on the battery and spin to work.

With it spinning and grounded, voltage between the 1 wire post and the case should be like 14V. And if it's connected the battery, that should be 14V too. And, go back to ohms on the multimeter, between that post on the alternator and the positive post on the battery should also be low.

(ohms is a measure of electrical resistance. there is always going to be some, but not a lot on a working circuit (i.e. a wire, one end to the other). the "ground" on a car is simply using the frame and chassis for a negative circuit.)
 
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Your voltmeter has ohms? probably have to move a lead from one socket to another on the meter... Put the two test leads together and make sure it's 0 (or a really small number). Put one lead on the negative battery post and another on the other end of the negative cable (bolted to the frame), should be low, under 100 for sure. Move the test lead from the frame end of the cable to the alternator case (just wherever on the outside of the case), should still be low, under 100. If so, alternator is grounded.
I have continuity between the alternator case and ground.

So a "1 wire" alternator (didn't you mention having one?), based on that name, should just have to spin and have one wire to the positive post on the battery (it gets all hidden and muddled and not directly connected through the harness, but, you really should be able to just jump a wire from that one post to the positive battery terminal). I actually get a little lost myself on how alternators and regulators work together and what else is needed, but having researched "1 wire" alternators because I've been considering upgrading (I still have 30 amps...), my understand is all that should be contained in the alternator, it has to be grounded, connected to the positive on the battery and spin to work.
I have continuity between the alternator positive post and the positive battery terminal. The 1-wire alternator does have an internal voltage regulator. The path from the alternator to the battery is a mystery as it disappears into the wire harness, but I suspect that it is going to the ammeter on the instrument cluster before returning to the battery.

With it spinning and grounded, voltage between the 1 wire post and the case should be like 14V. And if it's connected the battery, that should be 14V too. And, go back to ohms on the multimeter, between that post on the alternator and the positive post on the battery should also be low.
Spinning, grounded, and revved (a 1-wire needs to reach a minimum speed before it starts working, typically ~1,000 rpm on the engine), I get .1V measured between the positive post of the alternator and the positive post of the battery. I think that .1V is the minimum my meter can register.
 
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Spinning, grounded, and revved (a 1-wire needs to reach a minimum speed before it starts working, typically ~1,000 rpm on the engine), I get .1V measured between the positive post of the alternator and the positive post of the battery. I think that .1V is the minimum my meter can register.
Measure that between the positive post of the alternator and ground (case of the alternator or negative terminal on battery).

The positive post of the alternator and the positive post of the battery should be the same circuit, i.e. connected, voltage measured between them is showing the drop in current across the wiring, and shouldn't be significant. Would normal test that with ohms (resistance). at .1V, assume the wiring to the alternator is good.

It really sounds like you need a new alternator, but measure between it's positive post and ground first. The voltage it shows is probably from the battery, and the same as with the engine off at the battery (or really close). And, if so, no electricity is coming out of it, all the the wiring sounds fine.
 
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Spinning, grounded, and revved, I measure nothing between the positive post of the alternator and ground or the negative post of the battery.
 
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Or the “one” wire is bad... or the wrong wire is being used.

I thought someone suggested having the Alt tested.

I have continuity between the alternator case and ground.
I have continuity between the alternator positive post and the positive battery terminal.

And he mentioned plans to take the alternator to a parts store for testing. I'll put $5 on it failing?
 
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The plan was to take battery and alternator in for testing over the weekend. Wife had other plans for my weekend time, so that's happening this week instead.
 
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Had the battery tested. Good. Had the alternator tested. Fail. New alternator is on the bench. I'm putting in an oil cooler at the same time, although the wife keeps interrupting with tech support questions and errands. I'm beginning to understand the appeal of an off-site garage. With any luck I'll have it all put back together by midnight.
 

rkymtnflyfisher

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Had the battery tested. Good. Had the alternator tested. Fail. New alternator is on the bench. I'm putting in an oil cooler at the same time, although the wife keeps interrupting with tech support questions and errands. I'm beginning to understand the appeal of an off-site garage. With any luck I'll have it all put back together by midnight.


If you're lucky you could make a run across Magruder!
 
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20200822_192807.jpg

It's back together and on the road. I've actually got a reading off the alternator now. I drove in to Bozeman to grab a sandwich and for a shakedown. I have a couple small oil leaks from the new cooler, but nothing too major. All the lights work. It doesn't die when I apply the brakes. I'm pleased. I'll get the oil leaks buttoned up and enjoy the rest of fire season before winter comes.

I'd love to take it to Magruder, but not until I get a couple hundred miles of shakedown under it.
 
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The wife and I did a 120 mile loop to get some cheeseburgers. Battery was reading 12.22V before we left and is reading 11.96V now that we're home. I think I'm going to disconnect the line that goes from the alternator and disappears into the OE harness (maybe goes to ammeter before returning to battery?) and make a new line to go directly from the alternator to the battery.
 

rkymtnflyfisher

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The wife and I did a 120 mile loop to get some cheeseburgers. Battery was reading 12.22V before we left and is reading 11.96V now that we're home. I think I'm going to disconnect the line that goes from the alternator and disappears into the OE harness (maybe goes to ammeter before returning to battery?) and make a new line to go directly from the alternator to the battery.


Were you driving the 40? Or was it sitting in the garage?
 

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