Hey Guys,
It's been awhile since I was here but now I have a couple of questions. I have a 97 F-250 Heavy Duty(the early body style). For the last decade the battery indicator has been more or less right across the + on the little battery on the gauge. Almost like it was glued there. Then the other day, it dropped to just past the little battery on the - side. I know all this falls within the 'normal' range but the fact that it's something that has never happened has me wondering. I have had both the alternator and the battery checked in the truck as well as out of the truck. Both check good by two different shops. Now the battery gauge never gets past mid-way. Any suggestions or input would be welcome. Thanks for reading.

 

Take a voltage reading at the battery with the truck running, and most accessories off.

 

First of all, thanks for taking the time to respond. Ok, here what's happening. I charged the battery a couple of days ago. 6amp charge over a 24hr period. All cells read 1.275 specific gravity. This morning I did as you asked. With nothing extra running and the idle down to normal, a direct reading at the battery showed 15+volts on my hand held meter. The battery gauge inside the truck showed the needle on the 'M' in normal.
If there are any other tests/procedures you think I should run, let me know. Again, thanks for your interest and assistance.

 

Maybe the alternator belt slipping or skipping?

Vaya con Dios,
Chuck, CABGx3

 

That reading is good, maybe even a little bit high, but we will chalk that up to different meters possibly. Most newer systems run around 14.5v.

I can't explain why your gauge reads differently, but I am going to have to agree with the shops where you had tests done, it seems your charging system is fine.

 

I appreciate everyones input, thanks. I was letting things settle for a couple of days and it looked like my problems had taken care of themselves. I really don't like it when they do that, but what can you do. Then last night I drove to school, I teach a night class. It's about 15mi. had the lights, wipers and A/C on. Everything looked fine. The gauge stayed pretty much dead center. Then it was time to go home. The gauge stayed on the low side. Around the NA in normal, sometimes dropping below that when stopped at a light. No amount of engine speed would bring the gauge up to where it was before. This morning I measured the voltage at the battery, 12.6v, I started the truck and it came up to 14.5v on my hand held meter, with no accessories on and the engine at normal idle speed. The dash gauge was also back in the center. So I loaded the system, A/C, headlights on high. The voltage dropped to 11.2v and the gauge fell to just below the N. I increased the engine speed but it didn't budge. When I shut everything down and turned the engine off the battery still read 12.6v. Also I checked the alternator output at both the battery as well as off the back of the alternator. The readings were identical. I'm thinking a bad voltage regulator since the output in good when it is putting out. What do you guys think? Sorry it's so long but I like to include all the details. Thanks Again

 

From your symptoms, I tend to agree with the other post, the belt may be slipping. If that's not the case, your other option is to swap out the alternator. The regulator is part of the alternator, and you may be able to replace it separately, but I would replace the whole thing.

 

Hey Guys,
I'm back. I haven't been ignoring anyone, just gathering data. I've checked actual voltage readings at the alternator vs the gauge. As long as the needle doesn't go below the 'N' the alternator is putting out 12+v. It does tend to wander all over the 12-15v range though. I admit I'm not that knowledgable as far as automotive electrical systems but as I've stated before, the gauge has always been very stable in what I now know to be the 14v range. The belt isn't slipping. No squeal, it's not glazed or cracked and the tensioner moves freely through it's range.
I'm just going to keep an eye on things for now. If it starts to spend more time in the below 12v range, I'll spring for a voltage regulator. I hate the idea of replacing the whole unit because one small part has broken down.
Thanks again for all the help.

 

The other wear point inside the alternator are the brushes. High mileage units can have worn brushes.

 

Back again. I finally got tired of my alternator's behavior so I opened it up. Bad brushes!! They also wore deep groves in the sliprings. I have a new brush assembly on the way along with a voltage regulator, new bearings and new sliprings. Here are my questions. I got the pulley and the back cover off as well as the rear bearing but I can't figure out what is holding the center section with the diode pack. It doesn't seem to want to budge. Gentle tapping and prying has no effect. Also when I finally do get that out of the way, how do you get the old/damaged slip rings off the shaft. Someone suggested cutting them off but that would destroy what looks to be plastic insulators between the rings. Thanks for all the help so far.

 

Put in a new alternator.

See this thread... some fun posts:

https://www.ford-trucks.com/forums/9...-problems.html

 

I appreciate your suggestion but I really don't want to replace the unit, I want to fix it. As for the thread you suggested, the page won't display for some reason.

 

Sorry, I am not sure how it comes apart. Except for some of the really old style alternators, I have never taken any of the new ones apart. I believe I would be tempted though, if it turned out to be one of those expensive units that you are working on. So if you figure it out, write back in and let us know.

Believe it or not, in my area we still have two local automotive electrical shops that will rebuild your starter, alternator, etc. If you get stick with yours, you might want to see if you have a shop in your area. They may do the slip rings and let you do the rest, though you probably won't get any guarantee that way.

 

i just bought 95 f150 5.8 no bat cables need help

 

Start your own thread, this one is 2 years old and different subject matter.