HELP! Battery light...interior lights dim

PLEASE HELP!!! Well, my Windstar problem for today is...The other night I was driving & our battery light started flashing & then stayed on for quite a while. The interior dash lights & radio lights would also dim when the van was idling. (Also, van would almost die when you hit the gas.) They would brighten again as soon as you would hit the gas. Battery light went off and came on again later. Still having problem with interior lights dimming when not pushing on gas. Had alternator checked... it is fine. I think he said it was pulling 13.5 (???). Don't quote me on that! :) Anyways, it's fine. Now what should we check? My husband knows very little about vehicles and doesn't get in any hurry to fix whatever goes wrong with the van. Not very helpful when you have a Windstar that has something new wrong with it every time you turn around! Thanks for any help.

I don't think your alternator is off the hook... I would expect over 14 volts. Some AutoZones can do a pretty fair bench test.

But you've probably got other problems.... as 13.5 volts should keep everything going without dimming when the engine is running.

There are several cable ends and connections to be checked for cleanliness and tightness. You're on a "corrossion and looseness hunt". Don't overlook relay and fuse bases.

Sometimes a very old battery can be troublesome, but I would'nt replace the battery until the alternator output is up to snuff.

This sounds like a voltage regulator problem. The dimming of the lights at idle tells me that you are drawing on battery power and the sudden brightening when revving the engine up indicates more power being supplied by the alternator as it is being spun faster. The nominal volatge for a vehicle electrical system is around 13.6 volts DC with the engine on; if your alternator is pushing 13.5, that's ok, but it's not going to do a very good job at maintaining the battery's charge at idle. Make sure that alternator test is being done under a load.

Like 12Ounce says, look for loose connections, starting with your battery. Check your battery terminals and make sure they are tight and free from corrosion.

Side mount terminals can be problematic because corrosion can cause the cable mating surface to sit high and not make good contact.

For the negative side, there are probably two wires, one going to the block and the other to the chassis. I haven't specifically looked at these wires, so I can't tell you exactly where they go right now. There is a ground strap from the rear of the block to chassis on the right side of the van connecting underneath in the right hand wheel well.

Make sure you don't have too many electrical devices plugged in, as well, like a power inverter or a bunch of extra lights and such.