I just bought 2 new fleet farm batteries with in the last 3 months and a new 140 amp alternator from O'Reilly. I pulled a roughly 5000 pound hybrid camper home yesterday and didn't have any issues. When I went to start the truck today my battery light was on and I was getting 11.6-11.8 volts. The FICM was between 47-48. I've heard of getting bad alternators from the store, would this be the case? I have had a battery light come on for a few seconds once or twice since I got the new alternator also, would that be a bad voltage regulator from the get go?

Thanks in advance, any info would be appreciated.

 

The battery light only comes on if the voltage output from the alternator is insufficient. This can be either from a bad alternator or a bad connection at the alternator. There have been a few people who have had connector issues, but it's mostly an alternator problem.

Anytime the battery light is illuminated in the dash it is a warning that something is wrong at the alternator or it connections.

The system voltage you're reporting is typical with no alternator output.

 

I've been down the road with parts store alternators and I don't care for them.

I went through 6 Autozone alternators in 5 months before I got one that maintained a minimum of 13.5 volts. I took it to an alternator rebuilder, they upgraded the regulator and I saw the 14 volts my truck needed

This is why I upgraded and got the leece Neville 230 amp alternator. It bolts right in and gives me a consistent 14-14.5 volts idling or cruising. You need to upgrade your battery cables for it, but it's worth every penny.

 

It's also not uncommon while the gp's are still on.

 

I was looking at picking up a high output alternator from FICM Repair and then run all new battery wiring from alternator to the batteries. Sounds like that should take care of my issues. Looking at their site, should I go with a 230 or 185-190 amp with the overdrive pulley installed?

 

Definitely. But with a stock alternator he would have been used to seeing that. And we don't see a battery light with GPs on because the 110a is trying as best it can, while the voltage differential between the alternators output and sense connections are not excessive.

 

Similar experience for me. Currently running a 3G case alternator built by a local shop. They threw it on the test bench when I picked it up and it was making 183amps but I didn't think to ask what engine rpm that was approximating. If this one gives me any trouble in the future I think I'll try that LN next also. It seems to be holding up pretty well for the folks that have one.

 

Just put a new 140 amp alternator in after charging the batteries all day, here's an image of the old alternator where the connection was all melted, would this need a new connection from the alternator to the battery? The eyelet was fine but the rubber cover was a little black. Started the truck and the light went off, let it run for a few minutes and the light was on with 13.6-13.7 volts. Not sure where to go from here, park it until the LN 230 amp and rewire kit comes in?

 

Looks like there was a lot of heat being generated there. Dark boot, blue stud, melted insulator. Was the nut loose at all?

Was the last alt rebuilt or brand new? How about this one? How about the condition of the harness to the connector plug and the connector plug itself. Clicked in? Do you have a voltmeter with probes to check the connector pins?

I'll post Fords troubleshooting guide in a few minutes.

 

Everything was tight, harness was fine and plugged in all the way, and the nut was tight. The last one looked brand new the one I just put on looked like a rebuild. Just pop the connector harness off and check pins for voltage? I should have one around here somewhere.

 

These days I'm always suspicious of rebuilt alternators. Years ago I was in a commercial rebuilders operation with parts being boxed up for an auto parts chain and the best terms I can think of are "lipstick on a pig" or "someone else's problem". So I'm always looking with a jaundiced eye.

I went down and fired up my computer as I thought it would be best to give you Ford's troubleshooting guide rather then you getting various directions to go in. Three problem alternators is saying something is going on here. A bigger alternator with bigger wires is not going to deal with that.

Did you originally have a 110a alternator then go up to a 140a? Did you add any parallel cabling to address the higher output alternator, or modify the factory cabling at all? Not that it is absolutely necessary. I ran a 140a with the stock wiring for some time without issue.

I would also be checking over all battery connections, and going under the surface and checking the negative grounds too. With a dual battery system one bad ground is going to be a battery problem, but the alternator voltage output should still regulate off the other good battery role. NO, that's not true --- there still could be an issue with the ground point off the passenger battery at the front of the engine block by the harmonic dampener. A problem connection down there would send the alternator output spasmodic.

Here the Ford pages>

 

Give Ed a Call I think he has a line on L/N 230 amp units not sure how pricing compares with the DC units.

 

I just ordered one with a wiring kit, figured it wouldn't hurt to have the bigger alt and wiring, could also solve the issue. Haven't been very happy with part store alternators so far. And I'm going to check all wiring when I install that and make sure I have good grounds.

 

I went right from the 110 to a 140 without any cable upgrades, I ordered a new Leece Neville 230 and wiring kit so when I install that I'm going to go over all wires and walk thru the trouble shooting steps if I still have issues after that

 

OK, good luck.