Cost: $25 (plus shipping) each gear, $3.00 for the bulbs Pros: Fairly easy repair, Working odometer, Easier to see instruments Cons: Delicate job, Working odometer (for areas where insurance cost is based in part on mileage) Time: ~3 hours
A very common problem in the BMW 635CSi is the breaking of the plastic gears in the instrument cluster causing the trip meter/odometer to stop incrementing miles. The most likely culprit of this would be gears made of a material not able to hold up to the temperature changes the poorly-insulated instrument pod might be subjected. After 15 plus years, the gears can become brittle. Most owners report their odometer fails after they reset the trip meter – particularly if the car is moving. Both of these actions – and in particular the latter – put a greater amount of stress on the gears than any other time, thus causing the brittle gears to break.
After determining which gear I needed, I ordered the replacement gear Odometer Gears LTD (please tell them Z3Bimmer.com sent you). They have reproduced gears made from a stronger, more heat tolerant resin material. The gears are produced using molds cast from OEM gears. I only ordered the one smaller gear (called E1). One of these days I may buy and replace the other 2 gears just so I won’t have to worry about them breaking.
These procedures are based on my 1985 635CSiA with an ///M style steering wheel and no airbag. I don’t have enough experience with other years and variations of the 635 to determine how many variances you might experience applying these procedures to your car.
If you have the original dim 3w instrument cluster light bulbs, replacing them with a set of 5w bulb will make the instruments much easier to read at night. I used a pair of Sylvania 2825 European Lamps. I understand the Sylvania 168 will also work.
Some say it isn't necessary to remove the steering wheel. I did it simply because without an airbag, it is very easy to do and gets it out of your way. If you decide not to remove the steering wheel, simply skip this and the next step.
Using a bladed screwdriver, remove the center cap from the steering wheel.
Using a 22mm socket with a 3 inch or more extension, remove the steering wheel nut. Before removing the steering wheel, note the V shaped mark etched on the spindle, and the line etched on the steering wheel adjacent to the hole. These are the reference points for properly installing the steering wheel.
Remove the nut and the steering wheel from the spindle.
Carefully pull the module out so that the connector to the cable bundle at the back of the check panel module is accessible.
Carefully disconnect the wire bundle connector and set the check panel module aside in a safe place.
Use a 13mm socket wrench to remove 2 bolts on either side of the steering column. These hold the steering column in place. When removing the second bolt, support the steering column and gently lower it until it rests in place.
Remove the head light switch light bulb by pulling the bulb straight out of the yellow holder (green arrow).
While spreading the 2 locking tabs, disconnect the headlight wire bundle connector (blue arrow). Be careful to pull the connector straight out and to not break the connector.
Disconnect the speedometer wire bundle (red arrow). Be careful to pull the connector straight out and to not break the connector.
Disconnect the odometer wires (red arrows), the main SI board bundle connector (blue arrow), and the Gas/Temp gauge bundle connectors (green arrow).
Connectors should be disconnected in the direction of the arrows. Be careful to pull the connector straight out and to not break the connector.
Disconnect the fog light switch wires (red arrows) and the Anti-Lock instrument bulb (green arrow)
Be careful to pull the connector straight out and to not break the connector.
After these connectors are disconnected, the instrument cluster will be freed.
Lay the instrument cluster face down on a soft, well-padded surface. A throw pillow works nicely.
If you are changing the instrument cluster light bulbs, this is the time to do it.
Remove the two bulb sockets by turning the socket left 90 degrees to unlock it. You can use a 5/6 open end wrench to turn the socket.
Simply slide the old bulb out of the socket and replace with the new one.
Lock the bulb and socket back in place.
I also took this opportunity to remove the other bulbs (along the bottom of the cluster) and clean them. Over the years, they had accumulated a layer of dirt. After cleaning the bulbs, they too were noticeably brighter.
If you will be removing the tachometer for some reason, you will need to:
Remove the real-time mileage gauge wire (red arrow)
Press the tachometer locking tabs in the direction of the blue arrows, and remove the locking key by pulling in the direction of the green arrow.
Lay the cluster assembly face up on a sturdy surface.
The speedometer is attached to the circuit board by a pin connector on the circuit board. At the points indicated, gently rock, lift and disconnect the speedometer from the circuit board.
Be especially careful not to touch and damage the instrument needles. They are easily bent.
Set the remainder of the instrument assembly aside where it cannot get damaged.
Inspect the gears on the right side of the speedometer. Determine which gear(s) need(s) replacing. Remove the gear cover as necessary to get to the larger gears.
Remove any old gear fragments from the spindles. Gently shake out any gear fragments that may be loose in the speedometer gear case.
Reassemble and reinstall the instrument cluster in reverse order of disassembly.
One of the reasons for the breaking of the odometer gears is in part because of the material of the gears, but also because the dash under which the instrument cluster is mounted is not insolated at all. Exposure to sun and cold contributes to making the gears brittle. Before remounting my cluster, I lined the underneath of the dash with insulation material to help protect the instrument cluster from the Sandy Eggo heat.