Well for the last month or so iv been having this problem where my battery light will flick on when my rpms are around 3k and my lights will dim. At first it was only when it was at night going up the big hill from laughlin. And the last few days it did it around town a couple times. SOOOOO..... tonight i decided i would stop by autozone and let them test the alternator and battery. Both checked out just fine.... i guess... so he looked around and told me my tensioner for my belt was shot and that might be the problem. He was pullin on it and moving it. So i go about my buisness and a couple hours later im driving down the road and all my lights start dimming even my insturment panel, my battery light is on and my engine is losing power. I pulled off and limped into a parking space.

So Im sitting there my truck stays running and my friend reaches over and turns my headlights on and my engine dies and there's no power left to start it. We get another vehicle and jump my truck and i try pulling off the neg battery cable to see if the truck will keep running which it didn't so im guessing my alternator went bad.

So im getting ready to hit the sack right now so i can get to sleep and tackle this project tomorrow. I'm hoping some of you guys might have some advice, input or anything that could possibly help me track down this problem and fix it. Ill get back on here and check back in before i start tomorrow.

 

Replace the tensioner. Those SHOULD be replaced with the belt. They go bad.

 

The battery light flicker at high RPM's is exactly what my 97 did when my alternator went bad. On the other hand, jbrew is rarely wrong. Either way your truck is getting its power from the battery, so whatever is wrong with it, the alternator is not makng power.

 

I just figured since the battery and alternator tested good and that the tensioner is bad enough for someone to notice. - The belts slipping.

 

Well i dont think the tensioner is that bad. I hooked up a torque wrench to it and it took almost 50 before it clicked. But the belt is shot for sure. Its all cracked and what not. So idk im replacing the belt right this minute. I just stopped in to give you guys an update.

 

That's not how you test a tensioner lol. Regardless, if the belts that bad, -I have to replace the tensioner. Depending on miles, if around 100,000, you replace the idler pulley as well. Or you stand a good chance of much larger problems in the future.

I'll say, - "I told you so" now, instead of later,

Thanks for stopping in and best of luck

 

haha well that was my best shot at testing a tensioner. Im no mechanic. But anyways. Just replaced the belt and it didn't solve my problem. I hooked my battery pack up fired her up. With the battery pack still on the battery light flickers a little bit at idol. When i rev my engine up the light comes on steadily. I unhook the battery pack. My guages all die and all lights go off but engine keeps running. Untill i pulled off the negative battery cable. Yes i know thats bad on cars with computers but im desperate to get this running. Its my only vehicle and i have a job to go to. Luckily todays my day off

 

I'm really starting to get frustrated over this.

Pulled the alternator out. Had it tested. Its good
Pulled my battery out. Had it tested. Dead cell, Bought a new one.
Pulled my belt off. It was cracked. Bought a new one
And finally i replaced the tensioner

Battery light still flickering! The guy down at autozone hooked his little computer up and told me the alternator wasn't being told to charge.

I'm completely stumped now.

 

My 98 did the same thing started flikering at high rpms so I tested the whole system and everything was fine so I drove a round like this for a couple of weeks when my batt light came on for good. I replaced my alt and haven't had an issue since. Pretty mugh Everything for the alt is in cased in it.

 

Replace the alternator.
The brushes can't follow the comutator at higher RPM no matter what the testing says.
Brushes are either and or worn down , the comutator has rough surface.

 

The alternator isn't being told to charge ? Was that his exact words ?

I think Bluegrass probably nailed it. If there is no charging output (battery light illuminates), the battery will quickly discharge of course. You may have 20 minutes to an hour of driving time before everything goes dead and the vehicle shuts down. Here's a little diagram that might help.



You can pull the regulator and check the brushes. Who knows, they may just be sticking, bad wire or spring. I worked on one where the brushes jammed. - Both of them.

The Reg attaches here -



These are the brushes in the reg. They were jammed in this pic. -



Worked loose and cleaned in this one -



_______________________

Give it a shot, it might be an easy fix.

 

The belt/tensioner may very well be the problem.
Personally I don't have complete faith in AutoZone for diagnosis. To me it sounds like you have a dead cell in the battery. Pull the caps off the battery and ;
1) put a volt meter across the pos and neg posts..Should read 12v
2) put the neg probe on the neg post and the pos probe into the battery water closest to the neg post...1 1/2 to 2v reading
3) now put the neg probe into the water in the first cell and the other probe into the
second cell should also read 1 1/2 to 2v
4) repeat this process on all cells (neighboring cells) if you get a low reading or no reading you found a "dead cell"

Or you can keep the probe on the neg terminal and check each cell with pos probe and the value should go up by 2 volts per cell.

It is possible that with the belt/charge problem you have damaged the battery, hope not!

Good luck

 

Also, you can test your charging output (@ idle). First , it should be stable,- between 14 and 15 volts I believe. I can't recall the exact charging output spec. Somewhere in there. You'll need a multimeter.

If you need a Alternator, - I would stick with Motorcraft personally. That's probably the best you can do. I don't know of any others that are any good lol. Unless you want to build your own.

 

Yeah haha. It took 3 of them to hook my alternator up to the machine!... These pictures are great. I was going to take my alternator down to napa tomorrow and get a new one but now i think i'm going to take it apart and give it a shot. I didn't know how hard it would be to take it apart but you make it look easy enough.

 

I just had this EXACT issue. Battery light flickering at high RPMs going up hills. Then it started doing at lower RPMs too. It is definitely your alternator. I lean towards the "worn brushes don't make consistent contact at higher RPM theory". I replaced it and it's been perfect for the last 2 months.