Battery Guage Spiked and Truck died
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Mountain Pass
Joined: Nov 2016
Posts: 125
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Battery Guage Spiked and Truck died
So my truck started making an odd whistle/whining noise on the way to school and the battery guage went all the way to the right. I turned off the radio and headlights to see if that dropped the guage back down and it seemed to help. As I was pulling into the school parking lot, she died. Battery light was flickering on and off since the whistle started. Truck is 100% dead, no dash lights or gauges light up. What the hell happened?
Senior User
Joined: Jan 2012
Posts: 472
Likes: 5
From: Somewhere in the universe
Either the battery needs to be replaced or the alt went out.
The only thing the battery is used for is to start the vehicle and run eccessories. After the truck is running it should be able to stay running off just the alt. However if the alt is dead, the truck will run off the battery until it's drained. Once it's drained, the truck will shut down. This would be a faster process if your using eccessories.
Try jumping it. While its running, disconnect the battery. If the truck shuts down it very well could be the alt. If it doesn't shut down, it could be the battery.
Or just take the battery out, run it up to your local parts store and have them load test your battery. If it's good, you know it's more than likely the alt unless there's some other underlying issues.
The only thing the battery is used for is to start the vehicle and run eccessories. After the truck is running it should be able to stay running off just the alt. However if the alt is dead, the truck will run off the battery until it's drained. Once it's drained, the truck will shut down. This would be a faster process if your using eccessories.
Try jumping it. While its running, disconnect the battery. If the truck shuts down it very well could be the alt. If it doesn't shut down, it could be the battery.
Or just take the battery out, run it up to your local parts store and have them load test your battery. If it's good, you know it's more than likely the alt unless there's some other underlying issues.
Postmaster
Joined: Nov 2011
Posts: 3,533
Likes: 17
From: SW Florida
All the way to the right would be higher voltage than normal... no way a battery can do that. But if the voltage regulator on the alternator failed it could cause a voltage spike like that. Not sure how the circuit protection is set up on a 91... but I do know your truck has the fire-prone 2G alternator on it. If you need to replace it, you should seriously consider a 3G alternator swap. Search on here for the details of that.
And the first thing I would do is pull out a voltmeter and check across the battery terminals. Not the cable connectors but the actual terminal posts. Then check the cable connections. Then work your way upstream til you find an open circuit.
And the first thing I would do is pull out a voltmeter and check across the battery terminals. Not the cable connectors but the actual terminal posts. Then check the cable connections. Then work your way upstream til you find an open circuit.
Elder User
Joined: Jul 2011
Posts: 793
Likes: 2
From: Vernon, BC
Whatever you do, DON'T try to run your truck with the battery disconnected. That is an old school technique and we used to do it quite often. However, with the newer electronically controlled trucks it can/will toast some of your electronics. Especially your computer.
Lead Driver
Joined: Jul 2017
Posts: 9,601
Likes: 1,174
From: San Jose, CA
What Dday said! Old trick that a lot of us got away with, but it's an expensive lesson if you're not feeling like a lucky punk, as Clint would say...
Agree on the volt-meter. If you don't have one, you should. And they can be had cheaply too, including for free if you have a Harbor Freight nearby and need something. They give them away all the time.
Sure, it's a cheap one, but you don't need a $30-$200 volt meter to check a few things.
If you have a fusible link, it likely blew after being over-taxed.
But if your 2G alternator was acting like the fusible link instead, like they are prone to do sometimes, you may need a new alternator AND new pigtail/connector/harness/thingy for it.
You can purchase a voltage regulator and the harness connector separately, but many new and rebuilt alternators now come with a new connector to splice into your old one because the old ones were so failure prone.
Not one of Ford's better ideas...
Obviously from what has been said here, you'll be looking under your hood for burned wires, connectors or circuit protections.
Follow the two large Black wires coming out of the side of your alternator and see what you find along their length. Seems to me I remember they get buried in the harness on top of the engine fairly quickly, but you will hopefully be able to see any areas suffering some distress.
Good luck.
Paul
Agree on the volt-meter. If you don't have one, you should. And they can be had cheaply too, including for free if you have a Harbor Freight nearby and need something. They give them away all the time.
Sure, it's a cheap one, but you don't need a $30-$200 volt meter to check a few things.
If you have a fusible link, it likely blew after being over-taxed.
But if your 2G alternator was acting like the fusible link instead, like they are prone to do sometimes, you may need a new alternator AND new pigtail/connector/harness/thingy for it.
You can purchase a voltage regulator and the harness connector separately, but many new and rebuilt alternators now come with a new connector to splice into your old one because the old ones were so failure prone.
Not one of Ford's better ideas...
Obviously from what has been said here, you'll be looking under your hood for burned wires, connectors or circuit protections.
Follow the two large Black wires coming out of the side of your alternator and see what you find along their length. Seems to me I remember they get buried in the harness on top of the engine fairly quickly, but you will hopefully be able to see any areas suffering some distress.
Good luck.
Paul
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