I've diagnosed a bad alternator with my 2000 Expedition XLT Triton 5.4 V8. Battery light on, radio cutting off, repeated jump starts, pretty classic symptoms. Replacement looks pretty straightforward. Removed and trickle charged the battery but I have a question before I put the old battery in with the new (or rebuilt) alternator;

what are the chance there's a problem with the battery that may cause the new alternator to fail? I've heard that shorted cells in the battery can cause the alternator to fail, don't know how accurate or current that info is.

The old battery is an Interstate that's only about a years old so it will hopefully still hold a charge.

Are the battery testers at parts stores any good? The ones I've seen run what looks like an exhaustive series of tests that take 5-10 minutes, only to come back with pass/fail and no details about any possible problem. I have a DVM so I know how to check the voltage.

Any thoughts or experiences will be appreciated.

 

Welcome to the site..

If you diagnosed a low/no charge alt, chances are that's it.

If your meter reads a battery within spec after charging, doubt there would be any cell faults otherwise the voltage test wouldn't be within specs.. Same goes with a jump assist, if the old battery were internal shorted, it would/should affect the jump (to a degree) since the vehicles cables are through the excisting battery/cells. Sometimes with a completely calcified/shorted battery, removing the batteries cables and cabling your assist battery direct to the cars cables produces better use of those Amps!

If a batt shorted internally, it should draw the battery down. If shorted internally, jumped reverse polarity etc, fuse link should/would go open if the alt is pushing voltage to a shorted/dead head condition.

If there's any doubt on the batteries holding state of charge, best to just replace it...