Failing dashboard lighting 456M GT

I had a similar problem with my 550, turned out to be a loose connection in one of the connectors to the fuse box. Found it by wiggling the wires and watched for the dash lights to turn on and off. The female terminal in the connector block had spread apart a bit causing the bad connection. Hopefully yours will be as easy to find and fix. Good luck.

 

I don't know if the M uses the same dashboard lights rheostat as the pre-M model, but that's a fairly common issue on the 1995-97 cars. In short, the small thumb wheel in the lower dash on the left of the steering wheel that controls the dashboard light intensity starts misbehaving and generates the flickering you have experienced. It happened to my car too.

You can take the rheostat assembly out and clean it or (sometimes it works), or just replace it (not expensive).

 

+1

 

Hmm... indeed, that seems to point more in the direction of a fuse or fuse box/electrical connection issue (much like Ryan suggested above) - but that's where my armchair mechanical experience with this sort of things stops

 

Bump for an old thread... how do you.get the dash rheostat switch out?

Do i need to remove the 2 small screws under the hood release handle or does the switch pop out on its own?
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Also on a related note, is there a way to test the dash lights? Trouble shooting the parking brake light. It doesnt come on, i have cleaned and tested the switch and get good continuity. I assume the dashight is out.

Is it worth it to access behind the dash to swap out this bulb and is there an easy tutorial to remove the binnacle?

 

Removing the binnacle is straightforward and gives you access to connectors, lamps, etc. Start with removing the steering wheel fairings and work your way forward. Removing the dash is also not very difficult but A LOT more work and requires a helper to get it out of (and back into) the car.

The small panel that holds the hood release can only be removed including the bowden cable, so you need to start up front. But you can undo the screws that hold the panel and probably get enough movement in it to get to the reostat.

 

In most cases, the park brake simply provides an earth for the lamp. If the switch is ok, then it must be wiring or the lamp at fault. Does the switch have a good earth? Are there two wires on the switch? If so, the black will be the earth, the other wire (possibly orange with a black stripe) will go to the lamp. Make sure you have a good earth with an ohmmeter.

Many of the lamps will be supplied with the same (common) voltage, probably from the "Instruments" fuse. If the instruments and other lights are working, then the power side of the lamp will be ok.