Alternator VS old battery | Ford Explorer Forums - Serious Explorations

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Alternator VS old battery


Active Member
February 15, 2006
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City, State
SW Maine
Year, Model & Trim Level
1994 Eddie Bauer EX
I've got a 5-6 year old battery that may need replacing, I just want to confirm some symptoms before I replace the battery and kick myself for not replacing the alternator as well. The other night, I had the headlights, defroster (AC compressor engaged), heater blower motor running, and wipers running while at a stop light with the turn signals blinking. The RPMs and the batt voltage dropped so significantly (according to my gages,) that I was in danger of stalling. Is this a bad battery? Or a dying alternator? Should I head down to aut*zone and have them check my charging system and battery? Are those tests accurate enough for piece of mind? Thanks for any tips! Greg

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could easily be both but 5-6 years on a battery is usually toward the end of efficient life. and running just about every electric system at once is a big load on both. the test they do at an auto parts store are usually pretty reliable as long as whoever does it does it right.

My 93 got a new battery and alternator this summer, and still does exactly what yours did. I should have gone for the higher amp alternator. With that many accessories on, it's one hell of a drain on the electrical system. But like something9000 said, 5-6 years out of one battery is a pretty good life span. I'd replace it anyway.

If the battery is going, it usually shows up in the form of hard/not starting.

If the alternator is going, it usually shows up in the form of a low charging voltage condition or the system voltage dropping.

Sometimes this is nothing more than the brushes being worn down, and just replacing the brushes behind the voltage regulator for 10 bucks is all you need. Given the low quality of most replacement alternators these days, and the high prices, I'd go for a brush replacement, even if it means having to put on a new voltage regulator as well.

I have yet to see a charging system that bogs down because of a bad battery, since a vehicle can run with the battery removed once it's started. So your alternator is likely the culprit, or some other component of the charging system.

If the battery is going, it usually shows up in the form of hard/not starting.

If the alternator is going, it usually shows up in the form of a low charging voltage condition or the system voltage dropping
I'd like to share my experience with both of these scenario's. I was driving on XMAS Eve about 6 years ago on the freeway after starting the car and heading off to my girlfriend's. At the time, I had an 04' Ranger 4*4, and the light for 'charging system' came on with just the radio and defroster/heat. I did nothing for about 3 days since it was the holidays, and then, I finally went to Advance to have them load test everything. It was determined that with a 3 year vehicle that the battery was fine, and the alternator was the culprit. I called Ford and they wouldn't warranty it since the vehicle had more than 36,000 miles on it. Anyway, even with a 4*4 there were two different alternators that year (a higher and a lower output), and they needed the V.I.N. to determine which one I had. Naturally, I had the higher and more expensive one. I couldn't believe that mine was bad with normal driving and low miles, etc., but I guess it does happen. The response about the battery usually showing signs of hard starting before konking out isn't always accurate either. My current 08' Ranger 4*2 was tested last Dec. when the dealer had the vehicle for a warranty repair, and they decided to give me "a free 36 point inspection". They specifically mentioned the battery being fine, yet 6 weeks later, I was stranded at Wal-Mart after only letting the car sit for a couple minutes. I ran in, came out, and the Ranger battery was toast. I didn't even have enough juice to unlock the doors with my key fob. Any autoplace will usually test the system for free -- AutoZone, O'Reilly's, Advance, etc.

ive had a vehicle's charge light come on replaced the battery and its been fine since. and if your battery's not good then your alternator is always working at full capacity so anything else on top could cause a low system amp/voltage situation. depending on the problem and your wallet permits a higher amp alternator or an optima battery wouldn't be a bad idea.