88 5.0 Electrical / Alternator Problem

[Ford]

Rolling along in my 88 5.0 last night and the battery started to discharge. The battery was completely dead by the time I got home (within a half hour).

Obviously my alternator was not charging the battery. I left a trickle charger on the battery over-night and recaharged the battery for testing the next day.

With the battery fully charged and the engine off my volt meter reads 12.7 volts at the battery. With the engine running (no other electrical load). At 1500 rpm the volt meter reads 14.5. At 2000 rpm with headlights on and A/C running on high the volt meter reads 14.4.

So everything is telling me the Alternator is working fine. Why would it stop charging last night while driving and now be working? I did notice while driving that the battery indicator flickered. Could this point to a short in a circuit? I've checked the fuse link between the Alternator and the Battery. I suppose it could be a faulty starter relay. Battery cables look good. Belt tension is fine. Maybe the 5.0 fairy fixed it while I slept.

[Jacostang]

I believe you need to take the battery in and test it first.. It could have short inside it..

[JoeT]

If its an Optima battery Id replace it. Optima is not the battery it used to be since selling out to Interstate. I was havin tons of electrical issues with my Firebird, because my Optima was nearly new I never considered it to be the problem, so my stereo guy says Optima batteries are not good as they used to be. So he trades out my optima with a Delco battery to see if it fixed the issue. Sure enough not one problem since.

Im sure others will still swear by Optima, I used to as well. But after the issues I went thru Im no longer a believer.

[fazm]

let the car warm up for a while, then test the alternator, it may be overheating

[Mr. Austin]

I actually just has that issue with my 69 mustang with a 302. battery dies on me while idling at a sonic. I took my car to checkers (right next door) and they tested with my amps and extra fog lights and electric fan on and the alternator was perfect. Did the whole trickle charged tried again and found out what it was was my ground to the battery. It was touching like it should but unless someone did it i must have accidentally cut a small piece of the rubber around the wire off. I tightened the wire so it connected better and wrapped the inch whole in the vinyl tape. it held a better charge but played with my wires and tightened everything down and she has been fine since. All in all check you wires before you go pulling hair out. you will never know if they are all connecting correctly even if they look to be.

[Ford]

Thanks for the quick replys ... I believe I have an Interstate battery (green), I've been wanting to replace it with a Motorcraft anyway, now is as good a time as any. I'll give the wires another good look and also check the overheating possibility. Thanks guys!

[Ford]

Changed the battery. The problem has not returned ... yet.

[JoeT]

Cool!

[Jacostang]

Good News!!

[Mr. Austin]

great!