Is it the alternator?

[Anduril]

Originally Posted By: Whimsey
The alternator on my 2002 F-150 started triggering the red ALT light when the truck was at and above 2500 rpm, weird. A reman from NAPA replaced it and it's been fine ever since.

Whimsey

Faulty regulator was allowing the voltage to get too high at speed. Be glad you fixed it before things started getting fried.

 

[NibbanaBanana]

I had a 1990 Dodge van with a 3.9 V6. The battery ground went to a painted bracket on the top front of the motor. I forget exactly what it was for, maybe a tensioner or idler. Anyway, I changed the thermostat which required removing this bracket. Not too long after, the battery started getting weak and the charging system wasn't putting out it's usual. Took the battery to Advance and they tested it and said it was good. Took the alternator in and they said that was good. Got out one night and the truck wouldn't start. Putting two and two together finally, I moved the ground around when my buddy tried to start it and watched the spark show. Ran a new heavy ground cable down to an starter mounting bolt and it worked fine for the remaining years of it's life.

I think the best place to ground it is right on the starter. That's the highest load I guess.

 

[SHOZ]

On my '97 Taurus when new to me, was driving into work and all the sudden the car died and the warning lights all cycled. The car restarted but soon died again with the same symptoms. It was the battery being so low from the alternator not charging the engine control relay would drop out. Then with the load gone and the key still on the relay would pull back in. The dash lights flashed just like when first turning on the key.

First time the dealer changed the battery, second time they did the alternator which was the real problem.

 

[Vikas]

Don't *all* vehicles have a RED light when the alternator stops charging? If you are not paying attention to it. then that is a different story.

 

[SHOZ]

Originally Posted By: Vikas
Don't *all* vehicles have a RED light when the alternator stops charging? If you are not paying attention to it. then that is a different story.
It never came on on my Taurus. Apparently it only comes on when the alternator completely dies not when it is severely undercharging.

 

[Lubener]

Originally Posted By: Whimsey
Originally Posted By: 01rangerxl
I had a similar problem with a similar vintage 4.9L/5-speed F-150 a little while back. It was slowly dying electrically when driving...lost the digital odo, then the speedo and all other gauges, then a couple miles later the truck just died. Put a battery in it and it was fine for a few days, then it started doing it again, so put an alternator in it. Problem solved.


My 1989 F-150, 4.9/manual just up and died while on the highway. It had "real" gauges back then and I watched the voltage drop until the truck just died. A new alternator fixed it. The alternator on my 2002 F-150 started triggering the red ALT light when the truck was at and above 2500 rpm, weird. A reman from NAPA replaced it and it's been fine ever since.

Whimsey


I had the same issue w/ my 87 f150, 4.9. The regulator is internal to the alternator, so there wasn't much else that could be at fault.

 

[Kruse]

Originally Posted By: Vikas
Don't *all* vehicles have a RED light when the alternator stops charging?


Newer vehicles, perhaps. I can think of a lot of older vehicles that have nothing more than an amp or volt gauge.

 

[Vikas]

Well, having AMP or VOLT gauge is EVEN BETTER but that all depends upon driver scanning the instrument cluster once in awhile! That is a lost art.

 

[zzyzzx]

Get one of these:
https://www.amazon.com/INNOVA-3721-Battery-Charging-Monitor/dp/B000EVWDU0

INNOVA 3721 Battery and Charging System Monitor

 

[Vikas]

After plugging that in, worry yourself to death if you are driving a Honda. You *will* suddenly see 12.6V while the car is running!

 

[Barkleymut]

**OP here** I bought the cheapest reman I could find in a retail store here, about $80 after $20 coupon at Advance. Put it in last Sunday and have driven it twice since then and all seems good. I would have put in a new ground cable if that didn't fix it, but this truck is in really good shape for its age, it was my uncles and he does every bit of maintenance that is required and didn't drive in snow at all (its 2wd with no Lim Slip).

 

[zzyzzx]

Originally Posted By: Barkleymut
**OP here** I bought the cheapest reman I could find in a retail store here, about $80 after $20 coupon at Advance.


I hope you saved the receipt! You will need it.

 

[Barkleymut]

Ive never had a problem with a reman part from aap or autozone....what am i missing?

 

[HankMcMauser]

What I'd like to know is the cause of the alternator failure. A few years ago my daughters intrepid quit charging like above. She didnt have he $$$ for a new or rebuillt alt, so I opened it up finding worn brushes once inside. Had to wait til the followin Monday, and picked up a set of brushes from the reman. shop for $10. Took abiut 15 minuutes to install them. Its still going strong 20,000 miles later. Problem is its getting harder to find parts to rebuild things anymore the general consensus is to change thse offending assembly out for another one.r ather than diagnose its problems.

 

[zzyzzx]

Originally Posted By: Barkleymut
Ive never had a problem with a reman part from aap or autozone....what am i missing?


You have (so far) missed having a steady stream of alternators that fail and that you return to the store. After a while they will blame your car, but then you will buy a good one (I.E. - a new one or maybe a NAPA rebuilt one if they are still good) which won't go bad. I have had some of these [censored] rebuilt alternators last 30 seconds.

 

[Barkleymut]

a year later and the alternator is still doing fine