Strange Battery light fault

[jaatkinson]

I have a ford cougar 1999 that has a strange battery fault. I think it all started when I added an Amplifier to my sound system. Which worked fine for 2 days then the battery light started coming on and off on the way to work. So I unplugged the amp but the light still came on.

So at first I thought it was the battery so I bought a brand new bosch battery. The light however still came on... It does not stay on however it comes on and off while driving. I then replaced the alternator thinking it was that with a brand new one. But the battery light still was coming on and off. So I took it to ford they put it on the diagnostics and said that a fuse had gone. This can't be an ordinary fuse because they had to order it in. They replaced the fuse but then I got the car back the battery light was still on when idle. However if I reve'd the engine it went out... and stayed out for most of the journeys only come on every now and then.

Yesterday however the light came on again and it stayed on permanently. I tested the voltage across the battery and it’s the same with engine on and off so the battery is not charging at all. When I have done tests previously when the light comes on and off I normally get around 13.5 volts.. To 12.8 volts with everything on e.g. lights and heaters etc. I am not sure where to go from here I don't think its the alternator or battery. I have tested the link from the alternator to the battery and it seems good.. As does the earth..

Any suggestions would be appreciated.

Thanks

James

[kevxr2002]

honestly it probably is ur alt again. keep in mind if u changed the alt and turned on the car with the battery drained this can cause the alt to go bad almost imediately. if the wires are good, you have a new battery, and a new mega fuse then I would say it mroe than likely is the alt. do urself a favor and get one at autozone so u dont have to keep paying for one everytime you have to change it.

[LostRacer]

The flashing light usually occurs when the brushes start to seperate in the alternator as it spins up. Make sure all of the lines are tight on it first. It sounds like they replaced your megafuse. If your lines are tight and have good connection on all points your is most likely bad. Its not unusual for this car unfortunately.

Judging by your post you're not in the US. I'd probably look into a locat parts store or worst case scenario the dealership for a replacement.

[gamiller]

Xantheon has a similar problem. He replaced the battery. He then replaced the alternator everytime the light came back. He's on his fifth alternator since last October.

Have you ever checked to make sure that each ground wire is properly attached?

[AndrewM6097]

Also, check for arcing on the 3-wire pigtail connector on the alt.

[kwg2371]

I went through 4 alts already in the past 5 months in my car then I got a oem motorcraft one and havent had any problems since

[khhryst]

I have the same problem after I replaced my alternator with a rebuilt one. I told the mechanics that worked on it, they mentioned it may be the voltage regulator. They mentioned sometimes it goes out when the alternator does. 50 dollar replacement, but I haven't tried it yet. I'll post back when I do.

[khhryst]

I just found this also very interesting, I think there is a thread here on how to do this.
Automobile Repair/99 mercury cougar alternator replacement - Wikibooks, collection of open-content textbooks

While you are down there you can splice a jumper wire from the Red wire in the three wire plug over to the "Output" terminal of the alternator.

Question: Why?

Answer: It gives the voltage regulator a better reading than the factory wire that runs all over the engine compartment. The factory did the same thing in the later model cars. I think there was even a recall for this. If your battery light flickers when the engine is rev'd up than this is an inexpensive mod that may fix your problems.

[AndrewM6097]

Originally Posted by khhryst

I just found this also very interesting, I think there is a thread here on how to do this.
Automobile Repair/99 mercury cougar alternator replacement - Wikibooks, collection of open-content textbooks

While you are down there you can splice a jumper wire from the Red wire in the three wire plug over to the "Output" terminal of the alternator.

Question: Why?

Answer: It gives the voltage regulator a better reading than the factory wire that runs all over the engine compartment. The factory did the same thing in the later model cars. I think there was even a recall for this. If your battery light flickers when the engine is rev'd up than this is an inexpensive mod that may fix your problems.

I'm pretty sure this mod is for fixing strobing headlights. But i could be wrong.