Posted on 03/22/2015 3:30:31 PM PDT by waterhill
I am trying to help a friend with her truck. It is draining the battery. It is a 98 ford, which I detest (loyal Gmc owner). My meter is reading 12.76 V on the battery terminals. When I hook up the posi and jump my meter from the neg term to the neg cable, I get -12.76. This truck is sitting on top of a water puddle (we are wet out here this spring) and I refuse to crawl under it.
I know there are a lot of people here that have this, I just get creeped out by fords and lose my mind around them.
Help!!!
I can’t think of a way to do it that does involve putting an ammeter in series with the battery and pulling fuses one at a time. But that’s because I’m just a dumb engineer. Probably a real car guy will show up with a much easier method.
Good idea!
She may have invertently turned on a courtesy light of some kind. Could be the starting solenoid? Is it not turning at all? Clicking? what?
You are reversing the meter leads somehow when you take the two readings...
I don’t know about ford specifically, but most newer cars and trucks don’t like to have the battery disconnected. It resets the computer.
That’s pretty much the long & short of it, although if the regulator circuitry in an alternator goes TU it can short out and there’s only a fusible link (no fuse).
Ain’t carz fun?
Try Glove box light (not shutting off when closed).
If I follow, wouldn't leaving his voltmeter in series and pulling fuses eventually get him there?
Is that with the engine off or running? You need more like 14 volts with engine running.
You have an electrical problem, it has nothing to do with brand name.
1. Be not afraid.
2. You can stand in the puddle barefoot and not get a shock.
3.Putting the meter in series is not telling you anything aside from battery voltage
4. Put the battery cables on the battery. Start truck and jump if necessary.
5.Now read battery voltage from battery plus to battery minus. Should read 13.8 +/_
6. If it reads 13.8 alt is charging.
7. If its charging now you can disconnect battery, put a test light in between battery cable and battery- doesn’t matter + or -
8. Turn dome light override off first. Pull fuses one at a time until battery light goes out.
9. A bright says there is a draw....and a dim light is ok for clock, etc.
That is my next option
If you have only the positive cable connected to the battery, and the negative cable floating in the air, then you take your voltmeter and touch between the negative cable and the negative battery terminal, you should be reading 12.76 volts if the Negative (black) meter lead is on the battery and the positive (red) meter lead is on the negative cable. If you have the black meter lead on the negative cable and the red lead on the negative battery terminal, you’ll read the same voltage, but reverse the polarity, so it will be -12.76.
What’s the issue? Sounds normal to me. If your friend’s battery keeps dying, and it is over 3 years old, it’s time for a new battery. they make them so cheap these days that you’re lucky to get three years out of a battery. If it is a sealed type, replace it. If it is a non sealed type, pry open the caps and make sure the cells are filled with DISTILLED water to the indicator mark, or at minimum so that all of the plate material is under water by at least 1/4”.
“When I hook up the posi and jump my meter from the neg term to the neg cable, I get -12.76.”
Not exactly sure what you’re doing here, but if you have both battery terminals connected, you should measure around 12 volts from the pos terminal to any metal ground on the vehicle and 0 volts from the neg terminal to any metal ground point. If your battery is going down due to standby current, you’ll need an ammeter. But check the obvious first, such as courtesy lights that aren’t going off, etc.
That’s what I would do too. Check current draw. Realize that there is some drain 24/7 on it, such as the computer, clock, radio station memory, etc. Also check the alternator for it’s charging voltage and disconnect the the alternator when you pull one fuse at a time. A bad diode can cause a draw on the battery.
I just don’t like rolling in the mud, not worried about electrical shock.
You should have voltage in any car with a brain or clock, what you need to check is current. Anything north of 1A with key, lights off(including the courtesy lights) you shouldn’t be over 1A.
I think his objection to the mudpuddle was just that it was a mudpuddle. Wrenching and troubleshooting wires is pain in the ass enough without laying in water.
The terminal voltage tells us very little. It is an indication of the state of charge, not current draw.
What’s the current draw from the battery at one of the terminals?
It’s not going to be zero, but 3-5 mA would be normal to feed the memory in the radio. If you’ve got more than 100mA you’re going spelunking.
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