This morning while driving to work I noticed the charging system light would flicker if I got into the gas - only on a pretty good accelleration and only came on momentarily a couple times. My pickup is a 98 F150 with ~135,000 miles and the original battery and alternator. I was told like 2 1/2 years ago that my battery was loosing capacity but hadn't had any trouble so I said forget it (survived 3 more winters)- no problems since and no symptoms of slow cranking or trouble starting etc. Is it true that often if the battery starts going the alternator will go out too since it always working hard to keep it charged? I'm thinking after 9 1/2 years its time to think about changing the battery anyway so I'm not stranded someplace but I'm rather lazy about taking the alternator off to get it tested but would you suggest changing the alternator too? My battery voltage guage didn't seem to move and always stays in the middle of the normal range - I guess my real question is - is there anyway to tell with the battery light if its the battery, alternator, or both that are fritzing in this situation, or is there any easy way to tell without getting the alternator load tested? Thanks for any input.

-Montanafordman.

 

Most likely, the brushes in the alternator are starting to float due to wear.

If in doubt, do get the alternator tested. I'd just replace it or get it rebuilt by a local shop, if possible.

Doesn't sound like there's anything wrong with the battery from the information you provided.

Steve

 

I agree with project, the alternator is just worn out.

If I am not mistaken(I know my truck is this way), the voltmeter in the truck is like the oil pressure guage. It is nothing more than a glorified idiot light. It will provide a mid range reading until the voltage level reaches a set low reading and then it will read low. Similar for a high voltage level. Otherwise, it always reads in the middle of the range.

Your battery level with the engine running should be in the neighborhood of 13.8 volts. With the engine off, around 12.5. Good luck!

 

you can get a alt / battery tester i have a snap on ya271 not that much money.it should be charging apx. 14.6 volts. any garage can do this you dont have to take alt out to do it

 

Like everbody else has said more than likely your alt. when my battery was going bad the light wouldn't come onbut, the guage would read low,and when my alt went out the light came on. also the alt would test good off the truck but bad on the truck? took 2 remans to find a good one. this was on a 97 f-150 4.2. good luck.

 

My alt did the same thing when it decided to give up the ghost. If I had it to do over, I would either replace just the brushes (they are replaceable and easy to find online) or buy a new alt ($$$). I went thru a several remans before I got a good one.

 

Like everyone else said, most likely the brushes in the alternator are starting to wear out.
The alternator on my truck went out at about 130,000 miles. I just went down to Autozone and bought a remaned alternator with a lifetime warranty for $180. My truck is now at 175,000 miles and (knock on wood) the alternator isnt acting up, so I cant complain.
If you go to the dealer for an alternator you will pay at least $300.

 

Well, I was hoping to get some studying done tonight for an oral and flight exam checkride tomorrow for a new aircraft type (I'm a freight pilot) but decided getting there was more important so I bit the bullet and fixed it right in the auto parts parking lot. I was able to pick up my tools in the middle of the day and after flying back home I just drove straight to Shucks auto parts (thankfully made it there without dieing along the way) and pulled the alternator out and had it tested - failed of course so I ended up just buying a new one. I was short on time so I just did the alternator for now, think I might change the battery this weekend anway since its already 9 1/2 years old! Best battery life I've ever exprienced! Its NEVER died on me either! thats after 7 north dakota winters, 1 in Montana and the last in Eastern Washington! It's had plenty of -35 below zero starts without a complaint! Anyhow it still starts my rig fine but after that lifespan I don't want it to give out at a bad time.... so thats next. I once worked for Checker auto parts during college and saw many of the generic reman alternators returned but little to none of the high end autolite ones so thats what I went for. Lifetime warranty and 24 month roadside assistance with the purchase and after selling them I know those don't get returned so I figured it was the best deal. They cut me a 10% discount for looking it up online first (they pricematch, but I didn't even look at competitors or find a lower rate! ) and it cost me about $160 bucks. I even brought my manual, torque wrench, 18 inch 1/2 inch drive breaker bar for the belt to get the job done. and a couple wrenches and sockets. I didn't need to buy any tools but I always love these projects so I can think of the labor cost I saved - and justify having MORE tools! Anyhow using a little anti-seize and torqing the bolts to spec. etc. gives me some satisfaction doing it myself and doing it right! (btw my light doesn't come on anymore) Anyhow thanks for the replies!

-montanafordman

(now back to studying Piper Cheiftain aircraft systems! )

 

Old batteries can become resistant to charging & overwork alternators mercilessly, yet still start reliably on vehicles used daily. Often the same battery may go flat after sitting just a few days or quickly go dead if there's any problem starting requiring extended cranking.

Fortunately its a relative breeze to change the alternator on these pickups. My '98's battery lasted nearly 10 years also.

If its original I'd also recommend changing the belt & retaining the old one as a spare.

 

Yeah I'm thinking of replacing the battery this weekend regardless as more or less of a preventative nature anyway since its nearly 10 years old. I changed the serpentine belt a few years ago so thats still in good shape with no visible cracks or wear that I can readily see. I'm also hoping to get crazy and convert my truck to all factory power windows and doors, already have everything I need but I'll have to pull the dash to get the wiring done so I think I may change the heater core since I don't want THAT hassle coming up on me in the middle of the winter some time, I figure an extra 70 bucks is easy if I already have it apart vs. paying someone 8-9 hundred in the middle of the winter when I won't have time or motivation if it starts leaking.... Hopefully that will "age proof" it for a little while!