Help!! I have an issue thats driving me crazy. I have a 200 F250 superduty. It has an issue with the alternator, sometimes it will charge then other times not. I tried to diagnose the problem with the following. Checked and replaced batteries one was bad so got both new 1 month ago, (rechecked batteries yesterday low charge recharged now test good using Snap on battery tester charger). New alternator yesterday still no charge changed with one we have on another 7.3 that we know works still no charge. Wires at alternetor are in good condition and test good (orange same as battery reading ignition on and off) (green one same as battery reading ignition on and started) (Big red one same as battery reading). All battery connections tested good. With engine running using a snap on tester Alternator putting out 12.3 volts and only 30 amps but I have amps leaving the batteries (so its a slow discharge of the batteries even when running). Then after scratching and many calls the next time I tried it the alternator is putting out 70 amps and 13.7 volts like it should be (But I did nothing to change it) HELP!!! Could it be PCM?

 

Sound slike a bad alternator, or at least a bad voltage regulator in it to me.

 

Just happened to me. Idiot light on the dash never came on, but my volt gauge told the story. New alternator corrected it.

 

Just to make sure, you don't have dual alternator's, do you?

 

Negative. Single- oh-rye-lees that gets replaced ~2 years like clockwork, lol.

 

It is a single alternator system. I am open to all comments but I have eliminated it being a bad alternator or regulator. This is second new alternator in 1 month both tested good, also I used a good alternator I know is working off another truck we have but on my truck still would not work put it back on other truck it worked fine. Same with the brand new alternator yesterday on my truck it would not work but on other truck it worked fine. This lead me to believe the exciter wire was not working but not only tested good it allways showed power even thoe the alternator was not working. So maybe it was the plug in connection so I hot hired the exciter contact so the alternator was positivily getting power to excite the regulator still no change. But then like I said out of the blue without changing or doing anything different the new alternator started working propperly. Does the PCM control the amount of power the alternator puts out?

Thanks for all your input

On a side note I just got my yellow tape box from Riffraff. Cant wait to put my new parts on!

 

think i would take a serious look at all grounding points on the frame, look at the starter connections, coil connections, and also trace all major power wires for a rub through point, something is shorting or not making solid contact.

 

At this point you've gotta' be pretty sure it's NOT the 6G itself.

The connectors are a failure item on these, as evidenced by the number of places they are available in the aftermarket.

Here's just one example:
PantherFreedom.Net - Napa ECH-EC261 (aftermarket regulator connector for Ford 6G alternators) Pictures

That's where I'd be going next with this challenging chase.

SOLDER those wires when you replace the connector, and use shrink sleeving!!!!

Good luck chasing this electrical intermittent. Not much else more frustrating!

Pop

 

So I am also thinking along the lines of a bad connection somewhere. I will replace plug at alternator tomorrow and take aprt and clean big connector with multipul wires in it on top or valve cover and let you know what I find.

 

Still need help.. I cleaned all battery posts (which were all ready in good condition since batteries are only a month old) I also cleaned battery ground cables where they connect to block, I also cleaned main power lead into fuse box on the fender well, cab grounding straps and inspected all such cables. Still not working. I will loose power to the point everything shutts off (power windows, sterio, air bag etc) dash battery indicator will draw down to 9 volts then everthing will start working agin and charge will show 12 to 13 on dash. Tonight I will try fuse box inside cab and hopefully get my new plug in for the alternator. Any other leads is greatly appriciated.

Frustrated

 

"I will loose power to the point everything shutts off (power windows, sterio,"

I had a problem with a short behind my drivers door panel. The door plunger knocked the wire bundle loose and then rubbed a hole in a couple of wires. It was intermittent and affected windows and radio.

The other problem I had was the main wire bundle that 90'd down behind the blue pipe and between the air intake. It rubbed on the screw head to the air intake. I did a not so pretty red hose repair (pic included). Mine is an 02 though so you may not have either problem. Maybe it will help though.

Mike
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02 F-350 DRW

 

Just for ducks check fuse 6 mini 10A under hood. That is designated Alternator Field "A", regulator. Make sure it's good and that it is fully seated.

 

Okay here is an update and ITS STILL NOT FIXED! I also want to mention my truck is maticulously maintained its not a common 12 year old truck inside and outside including the engine compartment are like new. I dont cheap out on repairs or the parts for the repairs. So here is what I have done so far. I changed the plug that goes to alternator. I cleaned fuse boxes both the side where fuses are at and backside connectors in the engine compartment and cab (They were clean and good but trying everything) replaced all charging circut fuses (they were also good) cleaned negative cables and block connections (nothing bad), installed new battery cable ends (no corrosion old ones looked great), new starter, new starter relay on passenger fender, new glow plug relay, new batteries 1 month old (charged and checked they are good) 2cnd new alternator in 1 month and tried alternator from other truck that I know works, disconnected and cleaned big wire plug on top of driver side valve cover (everything looked great) , and yet still while I am driving the volts will slowly drop to around 8.5 to 9 about 10 minutes total from full to 8.5 volts (lights go dim, windows wont work etc) I will start worrying that soon the whole system will shut down but then in about 1 minute the volts will shoot right back up to 12.5. I know it sounds like the regulator but this alternator works great on another truck but not mine, also the other trucks alternator works on it but not on mine. I am running out of things to look for and Im getting tired of throwing parts at it. What would cause such a huge draw on the volts then allow it to come right back up so fast? Does the computer control the alternator output? What else could I look for? All of your help is appriciated.

 

Congrats on all the work you have done so far. Perhaps (for test purposes) you should build a test wire that will allow you to excite the alternator independently from the truck. At the same time, you could monitor the factory 'excite' wire voltage to see if it isn't sending the voltage signal when it should be. For your last question, I don't believe that a computer controls the excite signal on an 7.3, but others in this forum can verify.

Ultimately, you will have to get inside the head of the charging system and see what is really going on. when you said the volts 'shoot back up to 12.5' - they should be shooting up to 14.3-ish, if you're getting full alternator output (unless your batteries are so discharged that they suck down the alt. output greatly).

 

I would start by having your batteries load tested, it's free at most places? An alternator shop will test your alternator for free also. Check the phone book. Don't have the alternator checked at a parts house.

Mike
___________
02 F-350 DRW