I have a 98 expedition 4.6L and I'm having an issue with my alternator. When I install a new one, as soon as I start the car, the alternator dies. The battery isn't being charged (I connected a multimeter to the battery and the voltage goes down slowly). Also if I disconnect the battery, the car dies right away. I tried with a new battery from another car and the same thing happened. I have changed the alternator 3 times, and the same thing happened. What could be the issue? Where should I start looking? Thanks for the help.
98 Expedition kills alternators as soon as they are installed
- Thread starter srod70
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
stamp11127
Full Access Members
Are you having the alternators tested after installing them & starting the engine? Or, how do you know the new alternator has failed?
Can you follow schematics/wiring diagrams?
Can you follow schematics/wiring diagrams?
I was told that if I remove the battery after the car is on and it dies, that the alternator is bad. I also took the alternators back to the auto parts store and they tested them and said they were bad. I can follow schematics.
stamp11127
Full Access Members
Check the wiring. I would expect a short to ground is taking the vr out since you haven't mentioned seeing large sparks when connecting or disconnecting the wires.
If you have any of the old alts you can disassemble one and check the diodes and windings.
If you have any of the old alts you can disassemble one and check the diodes and windings.
Last edited:
PocolocoBob
Member
I'm having the same exact problem
I'm having the same exact problem with my '98 / 4.6. Were you able to fix the problem? If you did, please let me know what it was. I'm about to do the "Curly shuffle" on the stupid thing.
I'm having the same exact problem with my '98 / 4.6. Were you able to fix the problem? If you did, please let me know what it was. I'm about to do the "Curly shuffle" on the stupid thing.
Removing the cable while running will spike the regulator and burn it up. You may need to replace it again and don't pull the cable. A better way to test if it is charging without a volt meter is to put a screwdriver close to the center bearing on the back of the alternator. If it feels like a magnet it's charging. Be careful not to short across any terminals. A volt meter is the best way to test though. It will show somewhere around 13.4 to 14.4 volts if it works properly. It is possible that it could have a bad wire/connection of the field wire that passes a signal from the PCM that controls when the alternator starts charging. The PCM can also be an issue if it does not signal to charge.
I second that - disconnecting the battery while running not a good idea.
Also, at idle, depending on what else is turned on in the car the alternator may not put out enough juice to power everything causing a voltage drop and stalling.
I had a battery which failed and had various electrical problems going on even when running at highway speed with a good alternator so these components are really not designed to work independently.
Also, at idle, depending on what else is turned on in the car the alternator may not put out enough juice to power everything causing a voltage drop and stalling.
I had a battery which failed and had various electrical problems going on even when running at highway speed with a good alternator so these components are really not designed to work independently.
