Battery Going Dead -- Solved!

[jdudjak]

I had a problem when I first bought this 2002, 3.0 X5 in August 2010 with the battery going dead. The usual symptoms happened such as alarm going off in the middle of the night and the car not starting. I bought the car off an individual and the battery did not go dead for about a month after I bought the car. After replacing the belts, a battery, and squeaky idler and tensioner pulley, the battery still went dead expecially when it was cold. It gets pretty cold here in Germany and it gets cold quickly so I sent the car off to the local BMW dealer with german mechanics.

They ended analyzing every circuit and this is what they found. The following parts were drawing too much electricity when the car was shut down...

61356923954 Rain Sensor
64116923204 Blower motor resistor (also called final stage unit)
61356961141 Light control Module

The car was drawing 310 milliampers when the car was totally turned off and the car would never go into sleep mode. The normal current draw with a car in sleep mode is between 15 and 35 milliampers so the car was drawing 10 times the allowable amount of electricity when turned off. As a result, my battery went dead about every 5 days.

I just got the car back from the dealer with all the parts above replaced. Everything is working correctly and the battery is not going dead. Most notable about the repair is that the car is definatly going into sleep mode. The "P" on the shifter goes out after about 5 min of sitting around with the car doors shut.

If your car has the problem of the battery going dead and it is not going into sleep mode, then your light control module probably needs replaced. Also replace your blower motor resistor while at it. You can save money and disconnect your rain sensor and you will have regular pulse wipers.

One last thing, the light control module will have to be programmed after you replace it so you will have to take it into a dealer at some point. The light control module is located in the same general area as the blower motor resistor and it is easy to get at. The light control module is expensive and cost me from BMW $450 without installation.

It is really nice to be rid of the dead battery problem once and for all. I was considering installing a priority start battery disconnector. I am glad I did not.

-- jdudjak

[recklessspyder]

Glad to hear everything is fixed. Many people have replaced the FSR on this board for the same reason

[jdudjak]

Recklesspyder, thanks for the congrats. When looking for the silver bullet (single failed component) to repair the battery drain, I mainly read about the final stage resistor, and I never read about the control light module or the rain sensor being problems and major consumers of electricity when the car was shut down and parked. So I wanted to highlight that these could also be potential areas to trouble shoot when looking to solve the battery drain problem.

I have also read on this board that many people have problems with their car not going into sleep mode and I never read a fix for that. I wanted to highlight that replacing the electrical control module solved the sleep mode problem and an electrical consumption problem.

The battery drain problem may be a multi facited problem with no silver bullet, one item failure fix. By the way I love the silver bullet repairs and I thank this board and its members for all the troubleshooting help it has given me.