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Friday, April 25, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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January 22, 2004

Gauge Cluster Light Replacement

(Image: Rear of instrument cluster)A week ago I got in the car one cold evening (about 5 degrees F) to drive home, and when I turned the key (but before I turned on the headlights) I noticed the odometer LCD was barely backlit. The only light it was receiving was obviously cast from the backlighting of the adjacent speedometer and tachometer gauges.

For a second or two I thought the display might have been affected by the cold, much as the other LCDs are (they react slowly and are noticeably less bright when first turned on) but I quickly realized that because the service indicator LCD (directly below the odometer) was functioning properly it was likely a simple backlighting problem.

I began to get a little irritated at this point because I started to see dollar signs. I didn't know whether the LCD was illuminated via a simple indcandescent bulb or some integral mechanism that would require replacement of the LCD or (gasp) the entire cluster. I also didn't know how much of the dash we'd have to remove to remove the gauge cluster. Even though I'd seen the entire dash in pieces when we went looking for a cooling system problem some time ago, I never saw how everything was dismantled.

(Image: Closeup of bulbs used to backlight gauge cluster)I made an appointment to have the gauge cluster looked at today, and I'm happy to report it turned out to be no big deal. The E36 gauge cluster uses three "large" incandescent bulbs (pictured to the right) to backlight the speedometer, tachometer, and the odometer display respectively. Click on the picture of the cluster to see where they are installed.

The cluster also uses "small" bulbs for each of the status lights at the bottom of the cluster. Not all positions are filled because not all status indications are applicable to this car. For example, one of the bulbs is for the diesel version of the car -- it indicates when the glow plugs are on.

If any of these bulbs blows, you will need to pull the cluster to replace them...something that would be extremely easy to do if it were not for the fact that the steering wheel gets in the way. That probably wouldn't be the case on the E46 which has tilt wheel, but this car has a fixed steering shaft (that I actually prefer due to its simplicity).

Removing the wheel requires removal of the airbag, a process I won't detail here for fear of liability. It comes off with a minimum of effort, however, and exposes the jeezus bolt...a large bolt that holds the wheel on the steering shaft. Remove that and the wheel pulls right off, clearing the way for the gauge cluster, which can then be removed by pulling the two screws positioned upside down in the glareshield.

Two cables that deliver data to the cluster are then removed, and the rear of the cluster is exposed. All bulbs are contained in bulb "holders" (the green components shown) which twist out of sockets in the back of the cluster. The "large" bulb holders appear as though they were meant to be removed by one's hand, but must be removed with a longnose pliers or similar because they are recessed into the back of the cluster and difficult to grasp with big fingers. The "small" bulb holders require a screwdriver to remove since their head is simply too small to grasp.

Although only the center "large" bulb was out in my case, we applied the same logic to these as we did my recent brake lamp failure. If one bulb has failed and it has the same duty-cycle as other bulbs, a failure of the other bulbs is not far behind...thus they would all be replaced. Also, while the headlamp switch bulb does not have anything to do with the cluster and can certainly be replaced without pulling the cluster or the wheel, I had my mechanic replace that bulb as well because it didn't cost me anything additional to do it at this time and because that is one of the few bulbs in the car that burns day or night...as long as the ignition is on.

Since I knew I was going to get hit up for 0.8 hour labor to replace a couple bulbs and the process would only take about 25 minutes, I asked my mechanic ahead of time to do a few things:

  1. give it a bath to shed the 60 pounds of road salt clinging to its exterior
  2. check tire pressures, since I'd been too lazy to go out in the cold to check them the last couple of weeks, and
  3. look at the driver's side seat belt height adjustment roller. It had been making subtle (but repetitive and annoying) squeaking noises whenever I'd go over a bump and my body would move sufficiently to tug on the seatbelt. He checked it out and wound up replacing a couple thin washers that help center the roller and prevent noise like this. He also gave it a quick shot of spray lube and...voila! No more noise.

While I was in the shop taking the pictures, we got on the topic of replacement of the center armrest, the leather on which is totally cracked and horrible looking. I went over to the parts desk and priced it...about $180, roughly half of what it was a few years ago when I priced it. For grins, I also priced a new steering wheel, in the hopes that I could get new leather for a reasonable price...no dice...about $400. I'll pass...for now, anyway, as the existing wheel is still in fairly good shape.

Oh, incidentally, the E46 cluster is backlit using LEDs...which is very good because E46 owners probably won't have any backlighting problems for the life of the car. However, if they DO go bad, they're not individually replaceable. My mechanic says you would need to buy an entire cluster, and something tells me that the parts alone would cost far more than the $85 I spent today.

** Jeezus Bolt...a colorful reference to what a driver might say if the bolt ever broke and the wheel came off in one's hands. See also "jeezus nut", which is used by pilots of certain helicopters when referring to a critical attachment bolt in the rotor system(!)

Parts $8, Labor $72. Total $85, Total mileage, 88696.