Hello all, long time lurker and first time poster here, been solving a decent amount of issues since owning my R53 about 6 years ago and it has been quite helpful so far.

There is one issue that I can't seem to get quite the right answer for... My tachometer and speedometer have gone crazy!

About a year ago, in heavy rain, for a few days my tachometer and speedometer gauges would fluctuate wildly. The problem seemed to go away up until this winter where it has come back in full force.


Here is a list of the symptoms/causes I can figure out:

- All tachometer warning lights on during operation.
- Odometer only says "Code" and the trip button does nothing.
- When car is off and keys removed, turn signal indicator in tachometer will turn on and off intermittently.- All gauges fluctuate, especially during higher RPMs.
- Heater keeps switching from defrost to regular heat as if my car had just restarted.
- This is an odd one... My turn signal no longer blinks the green light, but instead blinks my "Check Filler Cap" light...
- Zero physical changes; the rest of the vehicle operates as if there are no problems. No loss of power, no lights flashing, all lights operate correctly, radio and windows work fine, etc etc. Only issues with the gauge cluster and the climate console.

I recently replaced the alternator (and checked the battery as well) so I don't think it is a power supply issue. Most signs point to the tachometer being faulty and needing replacement, but I really need to be sure before I spend any more money on repairs as finances are a bit tight right now.

Thanks for reading! Appreciate any help

 

Do you perhaps have a sunroof, and did you ever notice water in the passenger footwell? Because, my money is on a clogged or leaky sunroof drain causing corroded connectors at the BCM (or a bad BCM).

 

I do have a sunroof, but haven't ever noticed any water at my feet. That being said, after a long period of dry weather followed by a heavy rain, I do smell a moldy scent that I can't locate exactly. The sunroof does go kinda slow now too but I just assumed that's the motor slowly dying.

 

Good chance your speedometer unit is bad. Also called the chrono. Best to find someone with the communication and troubleshooting software (like the dealer has). They should be able to tell you what’s wrong.

 

Check battery. Bad / going bad battery can cause issues

 

Try removing your tachometer. Sounds crazy but the tach will tie up the can bus and cause many problems including transmission and engine weirdness. The car is fine without the tach. Just unplug it and see if that helps.

I spent $1000 troubleshooting it and a forum poster suggested this and voila’ fixed. Go figure. Anyway, I just bought another used tach off eBay and it has been fine four several years.

good luck,
Peter

 

Did you ever get this fixed? My car is doing the exact same thing...same thing.... thanks

 

Any update on this? I am having a similar issue but my tach has nothing (no lights, haven’t yet checked voltage) and my car isn’t starting. Trying to figure out which issues are related to each other if at all.