CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Dumb idiot light?

I replaced the alternator two months ago. First with a rebuild. The battery light came on as I left the shop so I went back and had a new one put in. The battery light stayed on and the charge on t…he tester was 14+.Then replaced battery. The light persists with no particular pattern. It comes and goes whether moving or stopped.In every other way this car, a cab with 236k on it, runs beautifully. However I now get feedback through the radio when accelerating or raising/lowering windows.

Stop posting the same thing over and over. It’s not a dumb idiot light, it’s a dumb idiot.

Gee whiz, am new at this. Cut some slack already!

I think it’s a loose or corroded electrical connection.

Thanks I’ll have a look at that.

Is the voltage being tested at the battery or at the output terminal on the alternator?

What shape is the belt in? An old glazed belt may not getting a good bite on the alternator pulley.
With the engine off, place a socket/ratchet on the alternator pulley and attempt to rotate the pulley on the belt. It should be very difficult to turn. If it turns freely then it’s likely the belt is the problem.
It’s also possible for an aged belt tensioner to lose some of it’s spring tension and this will also keep the belt from getting a good bite on the pulley.

Thankyou I found the same recommendation at the Ford site and will persue that as well.

Will also test at output terminal. Excellent observation!