1989 Ford F350 Crew Cab. I drove for about a half hour and noticed voltmeter WAY down. Figured the alternator I'd put in less than a year ago went on the fritz. Replaced alternator in the parking lot, and I'm still not getting any love.

I'm going to have "my guy" look at it when I get it towed back into town. It's just not charging. Is there a fuse link or something else I need to check? I'm going to clean and double check all wiring before giving up. This truck has had electrical problems since I purchased it and it's getting old.

A little past history. Had starter problems to no end and finally did a home run with a ground cable straight to the starter. Solved that problem. It has some sketchy battery isolater I'm trying to figure out so I can get that out of the way.

When tested "in the car" the car guys said "bad diodes." However, when removed the original alternator tested fine.

 

There is a Ford TSB on corrosion and shorts coming from the charging plug of 2G alternators.

Procedure is to replace the rectangular plug with the two black/orange wires any time the charging system is serviced.

Its common for this pigtail to drain the battery or cause a no charge condition, sometimes it even catches fire.

Many of us have 'upgraded' to the later 3rd Generation alternator because of recurring problems.

 

I vote for the "sketchy battery isolater" that you are playing with is your problem.
Battery isolators have diodes in them too.

 

Would the sketchy battery isolator cause the new alternator not to charge in the truck but function normally when tested on the bench?

I have seen isolators drain the battery overnight, but only know about them on the house battery side.

Was the (no)charge reading taken at the battery or coming off the alternator?

 

No charge was taken off of the battery.

So this short is on the pigtail somewhere? I've been getting dead batteries also. I've been pulling the battery cable when parked to keep it from hosing the battery.

 

Is there a part number for that connector? I'm going to pull the battery isolater out also.

 

What engine do you have?
Why do you have a battery isolator?

 

Lots of part numbers!

Borg-Warner PT-780
Standard Motor Products S-542
Power Plug 4628011
KEM Parts 350-220
Pico 5711
Dorman 85123
Motormite 08622
NAPA VRA 400

Ford OEM kit E5AZ-14305-AA

 

I've got a 351. The truck was used to haul a gigantic camper and trailer around by the original owner. He chipped it and put in a fancy dancy exhaust. I wish he would have been a better electrician cuz his work was a bit on the sloppy side. He's also got a trailer brake. I've been meaning to clean up some of his crap and this is prompting me to do it.

 

fordbozo I'm in Seaside and have the same PO problems, an electrician he was not. If you need help holler.

 

Check the voltage at the alternator output terminal before anything else. If it's good there then follow the wiring to wherever it goes until you find the point where you ain't getting alternator voltage. That will be the problem. Probably the sketchy battery isolator if the guy didn't know what he was doing.

If the alternator is NOT putting out acceptable voltage then check the wiring to the regulator.

 

1st post 'when tested in store, tested good'

Could always "ground here to test" screw on back of regulator.
Output should jump to full field, ~16-17 V

 

I'm not in a super hurry just yet as my driver has magically made it back to the coast. I'm going to leave it at the mechanics for now as AAA+ paid for the tow from Tillamook to Manzanita. If he can isolate it then I'm more than happy to pay him.

One good (or bad) thing from the last problem I had him work on. He was as stumped as I was and basically didn't charge me a thing to work on it. Ended up giving it a new(er) brain which solved the problem. He didn't want me to spring for a new(er) brain and was trying his best to solve it without me laying out that expense. More on that problem in another thread.

Most likely culprit: The connector and charge wiring from the alternator which apparently are known problems. Thanks to members of this board I have a much better idea what could be going wrong.

My mechanic did mention trucks of this vintage are all having severe electronic failures now that they've been on the road for 26 years. It doesn't help the environment out here is extremely tough on anything not made out of top grade stainless.

 

...and the answer is:

Bad ground wire.

Now I feel kind of stupid. My mechanic only charged me $45 though, and since I have super deluxe AAA the towing was free. In my defense I replaced the ground cable less than a year ago and also added in a "homerun" ground line right to the starter to eliminate that stupid problem. Starts like a champ now though.

 

Where did you end up grounding? Same spot by the fender?