1985 BMW with lots of little problems....

Hi, bought a very used 1985 528e. The temp gauge, fuel guage, speedometer don't work. I have been told to check the speed unit in the rear for the speedometer. However does anyone know if these circuits are connected in anyway or is indicitive of a typical problem? I am new to these cars...Thanks

This could be due to various causes but there are two most likely ones since it covers several instruments at the same time. The first one is a grounding point under the steering column where a lot of electrical grounds are connected. Maybe it has become loose and is not completing the circuit. The second one is a little bit more pricey and it is a dead "SI Board". These cars calculate the Service Interval (SI) for oil changes and inspections with a board inside the instrument cluster (See those little green and red lights?). This board has rechargeable batteries in it that eventually die and leak acid on the electrical boards corroding them and killing connections and components. I had a dead fuel, temp, tach, instant fuel economy gauge and all came back to life after replacing my SI board.
You can find them on Ebay but make sure that you get the correct one for your car.
I guess another cause could be that one of the big connectors behind the instrument cluster has come loose also (there are 3, blue, yellow and white).

Good Luck!

Originally Posted by jimoreno

This could be due to various causes but there are two most likely ones since it covers several instruments at the same time. The first one is a grounding point under the steering column where a lot of electrical grounds are connected. Maybe it has become loose and is not completing the circuit. The second one is a little bit more pricey and it is a dead "SI Board". These cars calculate the Service Interval (SI) for oil changes and inspections with a board inside the instrument cluster (See those little green and red lights?). This board has rechargeable batteries in it that eventually die and leak acid on the electrical boards corroding them and killing connections and components. I had a dead fuel, temp, tach, instant fuel economy gauge and all came back to life after replacing my SI board.
You can find them on Ebay but make sure that you get the correct one for your car.
I guess another cause could be that one of the big connectors behind the instrument cluster has come loose also (there are 3, blue, yellow and white).

Good Luck!

I bet it's the SI board. Mine is on its way out.

Ditto on the SI board. Your speedo is prob fine if everything else has crapped out on the display.

when i bought my car the speedometer, temp. gauge, tachometer, oil service lights and inspection lights didn't work. I replaced the batteries in the SI board and now everything works except the speedometer and tachometer. (however the oil service and inspection lights come on at random so if there is anyway to disconnect them it would be desired at least for me)

I have also checked the speed sensor in the differential and didn't see anything wrong with it, so if anybody has anything else about the speedometer repair that would be nice.

I bought on of those aftermarket battery-less boards for my 1985 528e because the temp didn't work, the fuel gauge was spotty and a few other instrument issues. Worked like a charm. Found it on Ebay for less than $50. I reccomend them, forget the batteries, they are pains.