My truck has been killing my battery off and on for the last month. I charge the battery over night, when I put it in the truck the gauge reads fine but after it drive it for a little while the gauge starts moving from the R to the N but then it goes back up to the R sometimes. Other times it keeps losing it's charge but after some time it charges back up. Yesterday the battery went all the way down to dead and the truck stalled out. I thought if the truck was running it would keep running. Does this sound like the alternator or is there something else that could be causing this? Also if it is the alternator does it matter what ampage I put in. The truck is a 92 F-150 I6, manual windows, mirrors.

 

[updated:LAST EDITED ON 20-Sep-02 AT 08:56 AM (EST)]I think your answer is, "Yes!". I just replaced my alternator about 4 weeks ago (bad diode). Symptoms were very similar. I suggest removing it (extremely easy) and taking it to somebody (like AutoZone or Advance Auto Parts) to run a check on it prior to replacing it, though. It's better to have peace of mind, than wandering while your forking out $80.00 for a new one. Then when you find out the one you have is bad, you already have the core for trade-in.

Craig

 

Sure sounds like your alternator is bad. Our trucks, and for that fact almost all vehicles, run off the battery. The alternator is there to keep the battery charged. Some vehicles have more that one battery to handle extra loads. The truck will run as long as the battery can supply power for the ignition, when it gets loo low the engine will quit. With no alternator to keep the battery charge up all electrical systems will stop.

When you get your replacement alternator it will have a connector and many warnings to replace the original connector with the new one. Not doing this may cause your truck to start an electrical fire. It is very easy to change this connector. If you have any concerns about your mechanical ability take the truck to a shop and have them do it. This is very important. This same connector on my F-150 melted into a blob of goo just before the alternator died and I smelled it. I replaced mine with a 90 amp "lifetime" rebuilt from Direct Auto Parts and have been back 4 times so far to get new ones. It is not that big a deal to change this unit out. Two bolts, one connector and the drive belt, but having to do it every year or so is getting annoying. They keep honoring the warranty, but I would rather have a reliable unit (the voltage regulator on my current one is bad now so I will soon have to make the sojourn once again, sigh...).

 

>I replaced mine with a 90 amp
>"lifetime" rebuilt from Direct Auto Parts and have been back
>4 times so far to get new ones. It is not that big a deal
>to change this unit out. Two bolts, one connector and the
>drive belt, but having to do it every year or so is getting
>annoying. They keep honoring the warranty, but I would
>rather have a reliable unit (the voltage regulator on my
>current one is bad now so I will soon have to make the
>sojourn once again, sigh...).

Ah, the words of a wise man who has learned that lifetime warranty isn't everything.

 

Hey, check out Alterstart on ebay. They sell HO alternators for cheap. I put a 130A in my F-150 for a mere $88.

 

Okay, I went to the junk yard and picked up another alternator. I put it in and everything looks fine. The thing thats bugging me is that the guy at the junk yard said that the pulley on the new alternator should work but it's alot smaller then my original one. I tried to swap pulleys but I gave up because I couldn't get either of them off. I can't get the nut to turn. With the small pulley the belt is tight but that means the alternator has to turn faster. Will this burn the alternator out? Or should I leave things like they are?

 

What did the alternator come out of? Is it an internal or external fan?

I've replaced the one on my '89 F-150 from one out of a 93 with an internal fan. I think Ford changed the design on the little connector in late 1992 or 1993, b/c my '93 has a different style.

 

Came out of a 89 Thunderbird. External fan, everything is the same except the size of the pulley. I'm thinking that the one I had on was the wrong size and the new one is right.

 

Here's how to check for an internally failing alternator:

Turn off all lights, close the doors.
Remove the negative battery cable.
Get your multi-meter, switched to read AMPs, and attach the black lead to the negative battery terminal, and the red lead to the removed negative battery cable.
If you see a draw of AMPs, then there is something shorting somewhere in the truck.
Remove the big electrical plug from the back of the alternator. If it is the alternator that is the problem, the AMPs draw will go to almost zero. That is a sure sign that the alternator is internally failing.
If the AMPs do not go to almost zero, then there is some other short in the truck's wiring. Remove each fuse in turn until you see the AMPs reading drop. That is the circuit with the short.

BTW, my truck is on its third alternator. I made the mistake of bringing it to a Ford dealer the last time where they told me the battery was bad. Paid $145 for a new battery, and the next morning, the truck was dead. Did this test and found that the alternator had failed again (after 5 years). So much for dealer expertise!

Also, NAPA or other good parts stores will swap out the alternator pulley for you. At least my local one did.

 

 

I have the same truck, 92 f150 I-6 no power gadgets. My alternator has died 7 times since November 95. I have been using Pep bOys lifetime guarantee alternators. After the last swap I talked to an old mechanic- 80 yrs old. He says alot of the rebuilt starters, alternators, generators, and regulators are junk. They come from these large corporate rebuilding places. That means inexperienced workers using the cheapest replacement parts. He told me to go to a local shop to get the next one. It is a place where they charge more, but put better parts in and do it right. Also he made a heatshield from some thick sheetmetal and bolted it behind the alternator onto the intake manifold. It blocks the heat from the engine, my reegulator sits right above the exhaust header pipes.

 

Everyone check your oilpan for leaks. My I-6 was throwing oil up into the serpentine belt area. The belt got oily and the alternator did not work right. If you do have oil on your belt it must be replaced!
The belt absorbs the oil and cant drive the accessories with the correct torque.