Mzmkont

Hi all,

For the past few years, I've been experiencing some issues with my instrument cluster. To keep the story short, from time to time it randomly decides to "reset" itself and quickly dim when starting the car.

It all started about three years ago (the first real winter with the car) when I extensively was using remote Webasto. I began getting messages regarding battery discharge and the first "reset/dim" happened. Didn't think much of it and changed the battery to a completely new one AGM 95ah from Exide. Unfortunately, this did not help me in any way, the issue was still present and was there from time to time even to this day.

What has been done:
- The positive terminal which is going under the car was checked by the official BMW workshop twice, they didn't see anything wrong with it and reassured that it was good to go. They only mentioned, that the only way to check if the cable is REALLY good is to cut it and inspect it inside. Naturally, this procedure is quite harsh and could create even more problems (with sealing), hence I didn't go with it.
- The negative terminal going from the engine to the frame was changed as it was quite old and became expanded and greenish. Thought this had a good effect and fixed the issue, but unfortunately, it did not. (just a coincidence that this was changed after a massive pile-up of error codes on the dash and a low voltage when running. Voltage was in the 11-13V and always jumping around. After the cable was changed voltage was back to normal 14.5-14.9V).
- The car does not have any IBS-related codes or any codes related to anything to do with the cluster, battery or even charging. Also, another important fact is that the car does not show any battery discharge or battery leak.
- As mentioned in the beginning battery was replaced. Last year, when troubleshooting I replaced it once more under warranty - no change.

A good video that shows the problem: (please watch from 00:45)

The trip does not reset, nor does the clock. The only things that reset are consumption and average speed. No messages on the iDrive about the discharge or anything, car starts just as always normally.

I think I would live with this issue, but this winter, a few months ago, when the temperature was down in the negative 25s (Celsius) and the car was not moved for 3 days I was not able to start it. It just clicked and that's it. Got a jumpstart after which hooked the computer up and it showed that my battery was at 75%, meaning more than enough to start it. One note is that this did happen before changing the negative cable and this was the only instant where this car left me stranded, it always started without an issue with this problem present.

So, after this long story, perhaps somebody had a similar problem with their 5series? Did a quick look around the forum, but did not find anyone with the exact similar problem.

Thanks in advance for your input, feeling quite lost on what sort of a devil got inside the electrical system...

donpb

You could have an intermittent instrument cluster or a host of other issues (i.e. harnesses, connections, modules, etc). Thermal intermittent electrical issues are tough to chase down.

What are you using to read the DTC codes?

Mzmkont

Hi donpb,

many thanks for the reply.

Yes, the problem is not persistent. It mainly reoccurs when it's colder outside and even then, it does not happen all the time. Also, important fact that this happens mainly when the car was standing for a longer time (12h+), after the first start the issue does not repeat thru ought the day. In the summer this does not happen.

My electrician is using ISTA to read the codes.

donpb

Your electrician has a lot of work to do. He could try warming up modules with a heat gun once the issue presents itself. Or you could do so as well.

Mzmkont

Any exact modules in mind? How would heating them help to create the issue if it’s only present when cold?

Another idea, would a bad alternator, voltage regulator have any impact in this? I have no previous knowledge if any of them were repaired, fixed before. Although the charging seems fine 14.6-14.9 with no serious dips. Maybe this could be somehow connected with degrading the battery, not sure tho.

Thanks,

donpb

I stated to warm up modules "when the issue presents itself". An unrelated module could be affecting the bus.

It could be. Check the entire charging system first. If you can read the charge cycle histogram, that would be best.

Mzmkont

Noted, thanks. Will leave the car with him next week, see if he finds anything.

I have seen the histogram at the workshop once the negative terminal coming from the engine to the body was replaced, it looked all fine. Also, I constantly monitor charging via the cluster's menu. Most of the time it is at 14.6-14.9. Sometimes, at the start of the journey, it tends to be closer to 15.0-15.1 for a few milliseconds, but pretty much that's it, quickly drops to 14.8. Never seen any different numbers which would indicate any issues to me.