Speedometer Calibration

[MBA – 2000/5/27] The first requirement is a calibrated or proven test speed source. You can do it the old fashioned way with a stop watch and a set of mileposts. You can use a known calibrated car for comparison at 60 mph, or lastly, you can do it at a speedo shop. I use a speedo shop, Dicks Speed-O-Tach in Phoenix. You need to find a speedo shop that will allow you to adjust it yourself, and re-check it while you’re still hooked up to their dyno. All the literature says this procedure doesn’t exist, so you’ll have to explain to the shop operator that you know how to make the adjustment, you just need him to supply you a target speed. The higher the calibrate speed the better. Try to get them to supply a guaranteed 60 mph.

Before going to the speedo shop, you want to be as close to ready as possible so as not to take up allot of dyno time, which is how you’ll be charged. Remove both the lower dash panels on the left, and then the bezel that goes around the cluster. (for clarification, this is the piece that holds the TCS and headlight up / lamps off switches). Next remove the four screws that go in the four corners of the cluster. Take a small terry towel with you, and lay it across the top op the plastic covers that cover the steering column. With the towel protecting the lens, tilt the cluster down and towards you, till the lens is practically laying face down on the column covers. Once you understand how the adjustment is made, you’ll know how far down to go.

 The actual adjustment is made by inserting a screwdriver into a 'pot'  and turning lightly and in small amounts. When you tilt the cluster  down, you will see these 'pots' attached directly to the circuit board  at the back of the cluster, and visible thru a small slot at the back  of  the top of the cluster. There are two groups of two each. There are two  on the left over the tach, and two on the right over the speedo. Of the  two over the speedo, the one you want to adjust is on the left of these  two. For clarification, this would also be third from the left if you  count  all four.

Use only a non ferrous tool in the slot. Mark the screw before you touch it in case you mess up, you always know where you started. Unlike some pots, these are finite. Its one turn (360 degrees) total adjust ability. turning the screw anti clockwise lowers the speedo reading for a given speed, and clockwise increases the speedo reading for a given speed.

Its actually much easier than it sounds. Re-read the instructions before you go, and after the bezel is off, to make sure you understand them. I don’t know why its not in the book, but I got this procedure from a bona fide Acura engineer, and have done it many times. Its perfect with all the wheel size changes we make. If you have any questions, or problems with the instructions, please e-me.

Do It Yourself