Gauges and Instrumentation (part 2)

After some months of searching, I finally got an Ebay hit for an ’86-’88 Turbo Quattro Gauge cluster. It’s a fairly specific cluster needed as not all cars had an electronic speedometer/odometer, some models still had a cable driven unit. This ebay unit, showed 136K miles and the center LCD actually looked like it was supposed to. So, for $150, I took a chance, figuring at the very least, I should be able to get a new odometer motor out of deal. A motor which, thus far, hadn’t been available anywhere at any price.

Once the new cluster showed up, I immediately installed in into the car to make sure it worked, or at least take stock of the parts that didn’t. I turned the key on and I was immediately greeted with “bar: 0.3” in the center LCD, success!

I turned the lights on, and there was but a dim glow from the upper right corner. I started the car, everything just seemed to work, I went around the block, and counted 3/10 of a mile. Success!. I decided to run with this new cluster for a few days until I could get to replacing light bulbs, and decide what I wanted to do with regards to the odometer reading.

Of course, the next day, the odometer stopped counting at about 18 miles. Not unexpected, but an occurrence which, at this point, was very discouraging. At least I had the new gear set on hand.

On a day when I had ample time to mess with it, I engaged in major cluster surgery.

I swapped all the bulbs from the old cluster to the new, I swapped the rebuilt LCD control board in, I swapped the new capacitors into the speedo/odo control board. I disassembled the speedo/odo to set the mileage.

Audi special tool #F000RK

A fully intact and functional motor/control board!

The car showed, 189k when I got it, I’d been keeping my gas receipts, so I knew how many gallons I’d burned through. Taking the number of gallons times the EPA avg fuel economy, gave me 2200 miles. So, I set the odometer to 191k — good enough for a 35 year old car. I, of course, also installed the new odometer gear set, I even spun things with a long small screwdriver to be sure nothing was hanging up.

With everything buttoned up, I reinstalled the cluster into the car and took it for a test drive. I got 2/10 of a mile before it stopped counting. In addition the speedometer wasn’t working right, it would barely register over 20mph. I was beside myself. I took everything apart again, using my long screwdriver to move the gears inside the odometer, I could tell something was hung up, I pushed a bit and things started moving again. In a burst of optimism, I put the cluster back in the car and went around the block. 1/10 of a mile before it stopped counting.

I took a deep breath and pulled the cluster out again. I disassembled the cluster AGAIN, and pulled the speedo/odo pod out AGAIN. I grabbed my bag of alligator clips and jumper wires along with a 9v battery in order to simulate the input the speed sensor would send to the cluster in attempt to observe what happens. (I was so frustrated at this point, I didn’t think to grab a picture of this process). I was able to un-jam the works again with my trusty screwdriver, hooked up the wires and started simulating input (this is accomplished by making and breaking contact to ground very fast in the hopes of generating a square wave signal. I observed the motor doing it’s step, step, step, twitch, twitch, twitch. I un-jammed it manually, and simulated input. It would step properly for a bit, then start twitching, I would unjam it. I continued this for a while before I took the pod apart again to check for debris, to make sure nothing was getting hung up…nothing.

No problems here!

Back together and simulate. At some point it seemed to be getting further between jam-ups. When I hit a full mile on the trip meter, I started having some hope. When I got it to five miles, I said, okay, good enough, lets put it back in the car. I also cleaned and added a little lubrication to the speedo needle shaft, where it passes through a nut which holds the hole works together. That clear the hangup there…thank goodness.

On the next day’s journey, it counted 1/10, 2/20, a mile and beyond. All the way to 22 miles….and stopped. I recalled, that when simulating input on the bench, resetting the trip meter sometimes had an effect. That action seems to jostle things just enough to sometimes shake things loose. Indeed, I reset and it and it started counting again. It got to some number of miles over the next few days. I stopped and topped up the tank and reset the trip meter. I was determined to finally be able to calculate my gas mileage. The Board computer, which displays through the center LCD was showing something silly like 60 mpg, which was clearly wrong (Will address this in another post). As I type this, the tank is near empty and the trip meter shows 257 miles. Honestly, I’m a little afraid to reset the trip meter, but I imagine whatever it was getting hung up on has clearanced itself.

So that’s it, it took 10 months of ownership, about $200, countless hours worth of poking and prodding, and countless remove/replace cycles of the cluster to get everything to work as it should. I must really like this car, because the time and heartache investment in just the instrument cluster, is objectively not worth it.

Note: This work was finished in at the end of December. It’s now beginning of April and everything has just been OK with the cluster! We’ve counted almost 2000 miles without missing a beat!


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