Pitster

2005 545i with ~ 145K miles. I've had a recent problem over the last months that has progressively gotten more frequent.

When first driving there seems to be a pulsing of power. The radio goes in and out and the interior lights pulse for a good 15 minutes and then it goes away and drives fine. Sometimes, after the pulsing, the Dynamic Drive shows a malfunction and becomes disabled and immediately after, drives fine with no pulsing.

Yesterday I put my meter on the terminals and watched the voltage drop to 11.xx to 14.xx until the Dynamic Drive warning light came on and then it seemed to stick right at 14 vdc and drive fine. After letting the car sit, I went back out, started it, got a rock solid 14.xx vdc with no errors or pulsing and drove it straight for an hour, no issue...

I was going to pull the fuse on the Dynamic Drive for a bit and see if this is causing the issue. If it is not, I'm thinking it's an alternator or Voltage Regulator, but you would think I would get an alternator error, which I've yet to get after pulling all the codes.

As I was watching the meter, I could hear the clicking, almost like it was from a solenoid pulling in and dropping out with the voltage swings...

Has anyone experienced this type of issue before?

Hyper_545i

Pitster,


Definitely a voltage issue. These cars are very picky when it come to constant voltage. Very well could be the voltage regulator, alternator itself or the battery. I would take it some place to get the battery and alternator tested. I have an 04 545i and had various malfunctions come up including Dynamic Drive. My alternator finally gave out. And when it did, I got an Alternator Malfunction on my iDrive. That was a new one for me!

Pitster

Well, the Dynamic Drive went out, then the surge problem continued...as you said, it seems like a regulator or alternator. I don't "think" it's a battery as I am getting 11 VDC while the vehicle is running which I should ALWAYS get more from the alternator.

Going to dig into it more this weekend when I have time.

Notheld

whens the last time you replaced the battery? OEM or non? If OEM did you get it
programmed at the local stealer?


If non of the above apply... Check the alternator.
Thats what im doing right now at the moment.
Good luck

BimmerFan52

Sounds like the VR on the alternator.

You can just swap out the VR on the alternator, but if it is the original alternator at 145K I would seriously think about a new unit as the VR is among a number of things that can go wrong with an alternator.

Rebuilt units are available, but quality varies greatly as some companies don't do complete tear down, examine and test windings and other electrical components and replace bearings as well as other critical parts. Some schlock outfits only replace the brushes, VR and give it a new paint job.

Removing all of the crap required to R&R the alternator is a big job, so I decided I would only consider a new unit so I didn't have to do it twice (around $300 delivered). Probably even more important if you pay to have it done as while most rebuilt units come with a lifetime warranty, the labor is the big ticket part and you might have to pay for that twice if the rebuilt unit fails.

RE Ticking - You might check the belt tension and if it appears tight, loosen the serpentine belt and spin all of the idler pulleys and tensioner pulley to see if a bearing is going. Possible it is also the VR wildly cutting in and out and what you hear are contacts opening and closing.