I have a 2003 R50 with 140k. Battery light only turns on when I floor it or driven agressively. Connections seem to be tight. Car starts fine without hesitation. I accidently floored it for a while, then all of a sudden the speedometer did a reset. Where all 3 needles (speedo, gas gauge, and temp) would go all the way up

I already did a search so don't tell me to do a search. I know there are you people out there that do that stuff just to get a post.

Thanks

 

Mark... check the voltage of the battery when the car is running... if its around 13.5-14.5V then your alternator is good... if it isn't then your alternator has crapped out... also check the battery when the car is off... if its less than 12V then the battery is crap too... also the belt could be slipping or there is a loose connection somewhere...

 

Or it could be the voltage regulator on the alternator...

 

It could be belt slippage because this morning I checked and got 12.5 volts car off and 14.75 with the car on. connections are super tight because I had to shim one of the connecters. I never had this issue before I replaced the belt. What would cause belt slippage other than a worn belt. I replaced the belt a few months back. You think the belt they replaced was the wrong belt. I hope not because a cooper s belt is too long for an r50.

I took it to firestone and had them replace it. You think it could be one of the pulleys? The last thing I need to do is try to replace one of the pulleys. Taking off a belt is a pain in *** to do especially with only one person doing it. Do they make some type of belt spray to make them stick.

Thanks

 

Try checking your harmonic damper/crank pulley. It might be on its way out.

 

Was the 14.75 Volt reading at idle? If so, that's quite a bit high and points to a problem with the voltage regulator. 12.5 V with the engine off isn't great, but it's not too bad depending on how long the car had been shut off before you took the reading.

 

Sounds like a slipping belt or bad tensioner. My belt completely fell off and the battery light came on. I believe the light is illuminated when the system voltage drops below a threshold, which could happen when the alternator (temporarily) loses drive.

Changing the belt is virtually impossible without raising the engine (at least with my big hands).

 

Taking the passenger side wheel and well cover off and you can get right at it.