Hello all, 

I have a 2008 fiesta ghia that i use as a little run around for work. around 20-30 seconds after starting the car, the battery light comes on and stays on until the car is switched off. This has been like this for 3 years and there has never been an issue with the car starting or any other issues.

When the battery light illuminates, it cuts out the heated front screen, presumably as it is a high power user. Ive never bothered to look into this until recently as i'd love to have my heated screen working this winter for the cold mornings.

An auto electrician has looked over the car and confirmed that there is nothing wrong with the battery, the wiring or how the battery is charging. He has suggested that the fault must be with the regulator for the alternator rather than the full alternator itself. 

would people agree with this from experience?

Is it possible to buy just a regulator for the alternator rather than replacing the full alternator? The car is only worth about £800 so dont want to fork out £250 for a new part if it isnt necessary.

 

Thanks

What would it cost you to change cars? A car with this fault is not worth full market value (whatever that is,) and if your current car is sound then it might last a good few years more. At this level, a car's value is measured by its utility and if it is going to cost a lot of money to buy something only marginally newer it is a lot to tie up in a runabout. I would be looking around the dismantlers for a 2008 Fiesta alternator which ought to cost a good bit less than £250. Depending on the alternator fitted, parts might well be available and I would ask your auto electrician who the nearest reconditioners can be found. If he doesn't know, take everything he has said with a pinch of salt!

If you are not having charging problems, flat batteries, poor starting and the like, then it would appear that all is well with the alternator. I don't know anything about how you use your car but a few short trips a week would in all probability not be enough to maintain sufficient charge for the car to be able to work the windscreen, so I would first charge the car fully on a trickle charger overnight and see if it makes any difference. It ought to raise the battery capacity enough to work the screen temporarily.

I assume the  fault occurs under all conditions. If it only happens when you work the screen, then that would point to a different cause.

Start by knowing which alternator is fitted. A physical check and googling the numbers you find should point you to any spare parts availability. If you can get a regulator, (and I have known them to fail) then it is worth a try but if the car is charging correctly I expect that the fault is deeper in the alternator and my gut feeling would be to change it.

I've had problems with refurbished alternators before.  And have seen others online with the same experience.  I would now only buy used (if cheap/available) or new.

Usually this fault is caused by the SmartCharge wire breaking between the alternator and PCM.  But if a competent auto-electrician has checked that then it should only leave an internal alternator fault...

Agree totally with above: recondition, get a part (eBay "alternator regulator" brings up loads of options, including full alternators at less than £250), find a used alternator, would be the way I'd go or even new as the car owes you nowt, you know it and, as said cost to change will be likely thousands  for something unknown.
Only minor thing to add is that (2011 - may not apply to yours) heated windscreens etc, if managed by a BCM are switched on and off, as you say because they are large power users. Even when the indicator light is on, the screens etc can be off as their operation is being controlled.

The fault is with the Smart charge circuit as @TomsFocus has already said.

The alternator will have defaulted to the emergency charge of 13.95V which is the reason your battery has not gone flat.

The common problem is with the wire that goes to the Smart charge plug on the alternator. It often breaks or the plug corrodes.

PS: You need to find a new Auto Electrician.

7 hours ago, unofix said:

PS: You need to find a new Auto Electrician.

Will be interested to find the outcome of this as it looks like that wire could well be the fault - can it be bypassed with a new jumper wire or corrosion removed to test?
It is regularly suggested to check for wiring faults but reports of this being done and the report of any resolution doesn't often happen?