Hello from rainy Venice Beach, CA.

I've got a 1991 F350 XLT Lariat that I've slowly been putting work into. It was already in good running condition when I got it about a year ago, but have since done major maintenance/replacements. This one is probably simpler than some previous problems, but I'm trying to avoid looking like an idiot if I go to a mechanic.

Yesterday I started it up and the battery light flickered. No change in power, no trouble starting or loss of power while driving, but the gauge fluctuates like crazy, and at red lights dumps way down low. This flickering light/gauge problem only happens for about 5 minutes. The battery is from about 15 months ago, and about six months ago it seemed dead, but after peeking in I realized the terminals (and deep into the cables) were all corroded. I crunched up the cables and sort of broke up the corrosion, and wire-brushed the terminals. No problems after that, until now.

I know I should have just replaced the cables, but at this point, I'm wondering if they're creating the problem, or if it's probably definitely my alternator. Also! This has happened every time I've started the car since early yesterday morning, as long as it's sat for a bit. Not sure if rain/moisture could be a factor, either.

Any and all suggestions and advice welcome. Sometimes I can't get a word in edgewise at my mechanic and I'd like to not feel totally bulldozed.

Thanks!!
Christa

 

Corrosion is like rust........it never sleeps......judging by what you say is happening.......Replace the cables......I'd bet a doughnut that it will solve your problems.........and yes....damp weather will exaggerate the problem........

 

Even if it doesn't, sounds like you need em anyway.

 

Will do! Thanks guys


Christa

 

Perfect time to upgrade to a 3G alternator too.

 

You guys are surely getting your fill of rain. Guess the drought last summer won't happen this year?

After 25 yrs, those factory cables are probably junk. Get some GOOD ones and you'll be good to go.

 

Yeah, I don't know enough (anything) about alternators, so I'm wary of even making that decision. I wouldn't know where to start!!

Thanks!
Christa

 

What kind of battery cables are GOOD ones?


Christa

 

I like these guys, I'm sure there are others that are just as good. They aren't that much more expensive than the drugstore cables in the blister packs. Those are junk, in my experience. Just measure the length needed, and indicate the terminals you want. These are 1/0 gauge pure copper, and heavy duty insulation. They have negative cables too, of course.

http://www.ebay.com/ulk/itm/142081889300

 

Motorcraft battery cables are OEM and should fit like a glove.

Is your 1991 F350 gas or diesel?
​​​​​​​The wiring can be different.

If you find your truck sluggish or dead after sitting overnight it could be the diodes in the alternator.

As others have mentioned, if the alternator needs replacement upgrade to the later 3rd Generation style to avoid the fire hazard of your 2G harness.

 

Howdy! It's gas. Thanks for the suggestion. I really don't know anything about this stuff. It hasn't been sluggish at all and definitely not dead. Any idea the going rate for a new alternator (3g, apparently! ) plus labor? I'd love to get in there and change something myself but I've only done basic repairs myself.

Thanks!
​​​​​​​Christa

 

Christa,
You have a second generation Ford alternator.
The rectangular plug that has two black/orange charge wires and a white/black stator wire has a habit of shorting internally causing a no charge condition or even catching fire.

According to Ford's technical bulletin this should be replaced any time the charging system is serviced.
This alternator pigtail is widely available in the aftermarket.

 

Thank you! Payday is here so I'll be able to get the good stuff : )
I really appreciate all the help. Hoping the cables will solve the problem. It's intermittent- some days the light doesn't come on, and some days it blinks constantly. Still hasn't affected the power, but I know I'm playing with fire (and now I know I really am playing with fire! That's scary!)
I've been doing a little research on the 3g alternators but again, hoping I don't have to do that for a while. The truck has 180k miles on it but I know a lot of things were replaced over the years. Just not sure how long ago.

Have a great weekend! And thank you again.

Christa

 

Well, changing the cables and the alternator pigtail should eliminate any problem.

The 3G conversion will charge more at idle than your present alternator can put out at redline.... and it is no danger of burning up the harness.

I have a new 130A 3G from DB Electrical for ~$85 and they sell the conversion harness/cable you need as well.
If you feel like this upgrade at some point, we can help you with that.

 

That's really helpful information. Thank you!
I just called a shop and they said to just bring it in. I grew up with buying parts as cheap as we could find them and if we couldn't do the work ourselves (my dad and I) we'd take them to the mechanic we trusted. Now everyone who worked well with that approach is closed or dead, and I feel like I don't know what the etiquette is on bringing in your own parts. Hopefully these guys are responsive. I like them because they talk me through what they're doing as opposed to doing whatever and charging me like crazy, and because one of the guys has the same truck as me. I'm just feeling like I might not be able to get a word in edgewise about what I've learned (from you all) and what I'd like to try first.
Wish me luck! As I said, I'd prefer to do the work if I can, but I'm worried I'd do something stupid and kill the thing.

Christa