Red battery light

[Stevez4e85]

I have had a look on here but can't find anything.

My red battery light has come up twice in 2 weeks now.
If I turn it off for 5mins and back on the light gose out.

Anyone else had this?

Any advice would be appreciated
2.5i 2003

 

[mr wilks]

Time for a new battery , a new alternator or both , its that time of year that kills them off

 

[skelters]

Page 88 of the Owners Manual says....

https://www.bmwsections.com/docs/z4/

The indicator lamp for the battery
charge current lights up:
The battery is no longer being
charged. The alternator drive belt is defective or there is a malfunction in the charging
circuit of the alternator. Please contact the
nearest BMW center.

When was the battery changed?

 

[Stevez4e85]

Thanks for the replies. I have no history of the car before I got it. And had to change a few things to make it run right.
I guess new battery 1st and see if it continues.
Thanks guys

 

[Stevepj]

First step is to check the alternator belt for condition and tightness, if these are OK and the belt doesn't slip when you try to move it by hand then move on to checking the voltage in the battery and the charging system.
A good battery should show between 12.2 and 12.7 volts without the engine running. Then start the engine and check again, if the alternator is charging you should see between 13.5 and 14.5 volts and the alternator should be able to maintain that as you turn on lights, blowers etc.
If you don't achieve something similar to this then it's time to get your wallet out and start replacing parts.

 

[colb]

My money would be on the Alternator going bad, do the check with a volt meter as described by @Stevepj. Since the car dosn't have a voltmeter I have a small voltmeter that plugs in the Cig lighter to monitor the voltage. Had an alternator go bad on my Z3 no battery light but alternator was not putting out enough voltage, use ofg headlights at night, next day I had a flat battery as it couldn't put enough into the battery to keep it charged enough. Since that happened I fitted a usb/voltmeter socket to the dash wired up to the cig lighter circuit so I can now monitor what the alternator is doing and state of battery. Z3 has a unit inserted in a blank switch position and the Z4 has a round unit fitted to a new hole in the dash. Ebay for the units https://www.ebay.co.uk/itm/Voltmeter-2-Port-USB-Car-Charger-Outlet-Socket-Panel-for-DC-12V-24V-For-Honda/223514152105?epid=0&hash=item340a7b4ca9:g:rYsAAOSwDKBcuYY2
and
https://www.ebay.co.uk/itm/12V-24V-4-2A-Dual-USB-Car-Motorcycle-Charger-Socket-Adapter-Outlet-LED-Voltmeter/183640100633?hash=item2ac1cd8f19:g:S-MAAOSwvqFcpaZf
Round one also available with 1 x usb and on/off switch here
https://www.ebay.co.uk/itm/Quick-Charge-3-0-DC-12V-24V-USB-Port-Car-Charger-Socket-Digital-LED-Voltmeter/401897892497?hash=item5d92fb2a91:m:meEzXQefYOj3yWltUoa5O1Q
If you just want a plug in one here is one with temp guage included as well but no usb.
https://www.ebay.co.uk/itm/12V-Car-Cigarette-Lighter-Socket-Digital-USB-Power-Charger-Voltmeter-Thermometer/123999435883?hash=item1cdef13c6b:g:8pYAAOSwiaVd6AfW

 

[Stevez4e85]

Just ordered one cheers