I have a 94 Ranger with the 3L, 6 cylinder. The alternator died one day so I replaced it. The replacement proved to be bad out of the box (supplied only 12V). The second replacement was the same (just my luck). The third replacement seems to do the job but I have an anomoly.

When I drive around town, the charge needle in the cab periodically drops from 14V to about 12V and the battery light comes on. This happens mostly when I'm idling at a stop light but doesn't immediately go away when I get back to speed. After a few minutes the light goes out and the needle shows normal charge.

I have been driving with the problem for about a month now and the battery has never gone bad. However, the anomoloy is the same symptoms the truck exihibited before the original alternator died. This is a little worrisome since I never know if the charge needle is going to swing back to full charge.

My question is what can be causing this problem? I have double checked all the connections to the battery and the alternator. Everything seems tight and shows no corrosion.

I had the battery checked at the auto parts place everytime I got a new alternator and they said the battery showed good.

I've taken the truck to the dealer and they don't like the aftermarket parts I'm using and want to replace the alternator and add an auxillary voltage regulator. However, their diagnosis shows no actual problem with the system.

Any help diagnosing this problem would be greatly appreciated.

 

Are you hinting that you don't have the original Ford alternator system on it? What do you have?

 

If I assume that this alternator has an integral voltage regulator
I would say that is what is causing the problem.
Something in the brushes hanging up in their retainer.

 

The alternator that I used is from O'Reilly auto parts. I told them what engine I had, they forked over the part. It LOOKS just like the original, but it is not a factory Ford part.

 

Regarding the integral voltage regulator; since it is built in, are you implying that I should replace the alternator again? Just looking for clarification. I'm not opposed to doing that, I'm just curious if I am simply unlucky when it comes to getting parts.

Thanks

 

One more question:

I was rereading my Haynes Repair Manual for troubleshooting tips and it says to check the fusible link between the starter relay and the alternator. I have not been able to locate this item to check it.

However, based on the description in the manual, it sounds like this is an all or nothing kind of situation. Either the fuse is burned out, causing a short, OR it is intact. Please correct me if I'm wrong.

 

You theory on the fusible link is correct. If you have a voltmeter, or an extra person to sit in the truck, is it possible to wiggle and pull on the alternator wires while someone watches the voltmeter, without getting your hand caught up in the belts/fan?

Only other suggestion is a bad ground. I don't know how your grounding system is hooked up, but make sure the alternator has good metal contact all the way to where the battery ground is hooked(to the engine block on your truck?).

You have an intermittent problem, and I don't care how good of a mechanic you are, or what vehicle you are working on, these type of once-in-awhile problems are hard to find.

 

Replace the alternator ?

No,


I had this same thing happen on a Volvo that drove me nuts.

Driving down the highway everything was fine.....Then Outta nowhere,all the dash lights would come on making it look like the alternator wasn't charging.
After this happening for 300 miles,
I took the voltage regulator out of the alternator and found that the brushes were hanging up thus causing them to not touch the commutator of the alt (showing a no charge situation).

This of course was an intermittent problem and rectified by replacing the Brushes on the voltage regualtor.

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The fusible link that is being spoke of is in the main harness running from the starter solenoid to the firewall ,all wrapped up in black tape like stuff.

 

I would take it apart and check it out as was suggested. See if there is a low cost repair kit for it that comes with brushes and a voltage regulator. If it was mine and I keep having problems, I would swap it out to an external regulator type. I put a Ford alternator on a Datsun once because I refused to pay $180 for one.