So i have been having issues with my headlights and interior cabin lights dimming when electrics such as windscreen heating was turned on, I assumed it was my battery on its way out as I'd only installed a new Alternator 6 months ago.

Today on the way home from work the battery warning light came on and won't go off, we've checked the battery and much to my surprise it's actually holding a full charge, we also tested the alternator and that is charging as expected.

What else could cause the warning light to come on? Our current train of thought is a bad earth? The light didn't come on when we were testing stationary right up until we started to drive off them about 500m down the road it came on.

Could be a bad connection. 6 months since everything was stripped off and put back on is enough time for a significant amount of corrosion to build up.

The light comes on if 12v is being produced at the alternator, but not being produced by the battery (or vise versa). When the voltages are the same, the light turns off.

On 3/10/2018 at 11:16 PM, Luke4efc said:

Could be a bad connection. 6 months since everything was stripped off and put back on is enough time for a significant amount of corrosion to build up.

The light comes on if 12v is being produced at the alternator, but not being produced by the battery (or vise versa). When the voltages are the same, the light turns off.

I'm leaning towards it being a smart charge issue right now, i've ordered a new plug and lead, going to try switching it my next time off, i've been using the car with no issues and the battery appears to be charging fine despite the warning light, and other research has led me to go with the smart charge being faulty, and also suggests it's a common problem.

my mate had this same prob but on his Mondeo Turnier 2008 MK IV 1.8 tdci he got a new alternator on and the next day it done it again it turned out to be a regulator that was faulty on the alternator

21 minutes ago, lasthope said:

my mate had this same prob but on his Mondeo Turnier 2008 MK IV 1.8 tdci he got a new alternator on and the next day it done it again it turned out to be a regulator that was faulty on the alternator

I put the new Alternator in end of last year, it is possible it's a bad alternator, but i'd rather atleast rule out the cheaper fixes before trying a new alternator as it seems to be charging even if it's got issues.

mates was doing same warning light would come on then off done this for a week went to a auto place said needed new alternator 160 for recon got it home few hours later prob came back took it to motor world done a battery test with all lights on and heaters said it was alternator not working 100% and that was a day old lol

2004 Ford Ranger Edge. Couple of instrument cluster bulbs were inop. Made decision to change all instrument cluster bulbs to LED. This really became an educational experience. 

First no one [Autozone,NAPA, Advance, Kelly, etc] stocks these bulbs. The 2004 ranger instrument panel is unique. It was changed from the 2003 and in 2005 changed again. So to get a 

salvage yard instrument  cluster it must come from a 2004 vehicle. 

To purchase a complete instrument panel one must order it from a Ford dealership. Then it has to go thru a separate security procedure. Then go back to Ford dealership. Then dealership

must install it and "marry" it to your vehicle . Called a repair shop here in Atlanta that specializes in instrument cluster repair. They said they don't work on 2004 Ranger instrument clusters. 

Ordered bulbs on line. Waited 2 weeks [Comes from China on a slow boat] . Got order , 10 bulbs, takes 11 for 2004 ranger. Bulbs were made incorrectly. The correct bulbs have a "clip"

moulded into both sides of the base of the  bulb to hold them in place on the printed circuit board. No clips existed. Ordered bulbs again and waited another 2 weeks. Tested bulbs before

and  after installation. Found 3 that were no good.  So, now I'm down to 7 bulbs and need 11. Incidentally, at least some of these bulbs are polarized which is why they were tested before

and after installation . At this moment I'm waiting on more bulbs to get here on that SLOW BOAT. Very frustrating because this has been my primary driver. A three dollar set of Christmas

tree bulbs is designed and manufactured better than these bulbs. Ford had better "wise up"!!

Incidentally, does anyone know what would cause the "battery" lite [On the instrument cluster] to be illuminated dimly when the alternator is charging OK? 

Sid Norris, retired heavy jet pilot and A and P mechanic 

3 hours ago, [email protected] said:

Incidentally, does anyone know what would cause the "battery" lite [On the instrument cluster] to be illuminated dimly when the alternator is charging OK?

In days gone bye if it glowed dimly only at high engine RPM's then it was usually a faulty Zener Diode and was an easy fix because you could buy all the components. That was in the days before Smart Charging and I don't know if modern Alternators still have them.

Other than that it could be a faulty Earth (Ground) somewhere or a faulty Regulator.