Thread: OVERCHARGING ALTERNATOR DOES IT NEED TO BE REPLACED

I think I've read somewhere that the alternator is supposed to kick out a maximum of 15.5v, so 16v sounds a little out of spec.

I'm sure that someone who knows for sure will be along to confirm or deny that shortly.

Hi Andrew and does it stay at 16v or is it only at 16v when you first start your motor?

I have found that many battery places and auto elects do not understand the charging system on the D3 and provide poor advice as a result.

If your "garage" understands these vehicles fine but if not, I would be taking it somewhere familiar with D3s.

Garry

The car is at a well known LR specialist here in Melbounre's eastern suburb of Burwood, those in Melb would know who I'm talking about.

I asked them to look at the battery, as each time I start the car in the morning the low voltage message appears on the stereo. I've checked the battery and it shows about 12.5 volts before starting the car, their check has shown the battery to drop to 6volts under load, however they believe the battery's poor condition is due to it getting overcharged and cooking it.

I had this happen many years ago with a 1970 MGB, when the regulator died and the alternator run at 100% continually, you could see the battery bubbling.

I know the charge system of my modern D3 would be vastly different to the MGB, but was curious to see if someone else had experienced a similar problem and was a new alternator the only option, so far the service is now going to cost over $5k, ouch!!!!!!

Have you noticed a burning smell from the engine bay at all?

I would agree with the dealer, it sounds like the alternators screwed. Is the 16V directly from the alternator power, or is that at the battery?

Hi again kingo and as the battery is stuffed, before replacing the alternator, I would replace the battery and see if the alternator still runs at 16v continuously.

To cook a batty with as little as 16v, you would need to drive for very long periods and the battery would most likely have electrolyte spillage in the battery compartment.

Where as, if the battery is stuffed, the D4’s BMS may be “thinking” it needs to get a charge into the battery, and is running at 16v to try to achieve this.

If you get a new battery first, see if you still have a constant 16v voltage level after a 30 minute drive.

BTW, while 16v will eventually cook a battery, it will not effect anything else in the vehicle, plus, most alternator with runaway voltages usually read in the 18v mark, so a continuos 16v may very well be a software problem.