Gauge Cluster Differences Throughout the Years

[jnshk]

Not sure if this will ever be useful to anyone else, but I figure I'll put it out there just in case. Here is a list of differences that I documented while working on my gauge cluster project. If you've got any more details of the variations in gauge clusters throughout the years (or perhaps from different markets), please post them here.

List of noteworthy differences between 93 and 97 gauge clusters:

- 97 is prewired for vehicles with ABS and automatic transmissions--This includes a hold/overdrive lamp, ABS lamp, and low washer fluid lamp. 93 has the spaces for these lamps, but there is no overdrive cutout on the gauge face and the circuitry for all three lamps is incomplete. I think that in earlier years the clusters were only wired with the functions that their respect package included, while later years were wired to be compatible with all options.

- The "overdrive" lamp circuit in the 93 cluster appears to include a dimmer function, while the "hold" lamp circuit in the 97 does not.

- There is a 180-ohm 2W resistor for the fuel level gauge that jumpers a trace on the circuit board of the cluster in most years. It appears to be absent in many (if not all) of the 97 clusters. This resistor helps calibrate the fuel level gauge so that in earlier years it moves from F to E with the tank. In later years (which are missing the resistor), the needle goes past F and E. On a full tank, it floats above F until approximately 10-11 gallons and then begins to move. E represents approximately 2 gallons.

- Tachometer gauge face on 93 car shows partial red beginning at 6.5K rpm and full red at 7K whereas 97 only shows full red at 7K.

- Completely different oil pressure gauges. They are physically interchangeable, but the sender would need to be swapped as well.

- Completely different water temperature gauges. They are NOT physically interchangeable as the mounting bolts are located differently and the circuit is printed differently on the back of each cluster. They do however both use the same sending unit, so while you cannot switch the gauge between clusters, you can switch entire clusters and retain a functioning water temp gauge.

- UNCONFIRMED RUMOR: The speedometer/odometer is geared differently due to the earlier cars using a shorter final drive ratio. The speedometer seems to indicate a bit higher than the unit in my '97 cluster, but I think this is a natural variance between units and not necessarily an indication that the 1.6L clusters were geared differently. Both gauges were marked with "60 MPH = 1024 RPM" on the back, so I assume that they are meant to be calibrated the same. When the '93 unit indicates 60mph, the car is actually traveling 57mph. This is exactly the same as the '97 unit. However, at speeds above 60mph, the '97 unit appears to have less deviance from real speed than the '93 unit has.

- The earlier models had metal trim rings/bezels around the speedometer and tachometer, which are missing from the gauge clusters on later models.

[revlimiter]

I can add a few more.

- Extremely early clusters (90 only?) did not have the outer, lower indicator lights. The ones for ABS and washer fluid? The clusters didn't even have partitions for these lights. I've seen only one cluster without these indicators.

- The washer fluid light on every NA Miata has never worked. Ever. There is no sensor and Mazda never connected the wiring. And I've read a rumor that the ABS light is the same, though I cannot confirm that.

- 90-95 gauge clusters have the chrome trim rings around the speedo and tach. They also have a sort of flat finish to the plastic in the bezel that makes it look more grey. 96-97 clusters have no chrome rings. They also have a textured plastic that makes the bezel appear darker. The texture is similar to the rest of the plastic in the interior.

- The tachometer scale has at least 4 variations. I'm not talking about redline style or the different font used on M-editions. I'm talking about the spacing of the tick marks. 0 and 8000 are always in the same spot regardless of NA tach face. The rest of the tick marks move around slightly. Every one I've ever scanned has been slightly different. For example, 6000 comes up much earlier on NA8 tachs than on NA6 tachs (about 200 rpm sooner). And the 1000-2000 spacing seems totally up for grabs. Very subtly different on every gauge I've ever seen.

- If you consider the whole world, there is an almost endless number of speedometer variants. North America gets 0-140 mph. Japan gets 0-180 km/h. And Europe gets everything. I've seen 0-140 mph (usually marked NA95 at the bottom), 0-120 mph (usually Eunos Roadster imports), 0-180 mph (yes, 180 miles per hour) with the same scale as the 180 km/h but with a converter gear in the trans, and also 0-220 km/h. I'm sure there are more versions I've not encountered.

- The defroster light in NA8 clusters has its own wiring harness and circuit board separate from the rest of the cluster. It can be completely removed just by unscrewing it from the front bezel and threading the small connector through the soft circuit board on the NA cluster. You have to peel that soft board up slightly on one corner to do this. Many folks don't realize that and end up cutting the wires.

[jnshk]

- There is a 180-ohm 2W resistor for the fuel level gauge that jumpers a trace on the circuit board of the cluster in most years. It appears to be absent in many (if not all) of the 97 clusters. This resistor helps calibrate the fuel level gauge so that in earlier years it moves from F to E with the tank. In later years (which are missing the resistor), the needle goes past F and E. On a full tank, it floats above F until approximately 10-11 gallons and then begins to move. E represents approximately 2 gallons.

I can't edit my initial post, but I've got more information to add in regard to this note: After more testing, the behavior is not entirely as I first assumed. When removing the resistor from the '93 cluster in my '97 car, it did increase the scale range slightly, but not quite as far as my '97 cluster. Not sure if there is just natural variance between gauges or some additional design change that I haven't spotted. With the '93 cluster (after resistor removed) in my '97 car, the needle will hold at just above F and then start dropping when the tank is at approximately 11 gallons. It will then read semi-linearly down to E and it will hover there until approximately 1.5 gallons are left in the tank and then drop a notch below E.