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Speedometer not functioning

Joined
12 March 2020
Messages
349
Location
California
Hi prime!

A few weeks ago i went to get gas in the NSX and went over a dip in the road (nothing abnormal) and noticed my speedometer stopped reading anything but 0 MPH. i looked up a few other forum posts to see the consensus being directed to the VSS. I dont think this is the issue because my odometer and trip meter are both still increasing and im thinking if the odo/trip are functioning properly then the speedo meter is the issue somewhere in the line.

Any help will be greatly appreciated!

Best
Andrew A
 
A VSS signal failure of the earlier cars will cause an ECU error code. No error code, not the VSS. If the odometer and trip meter are still functioning, then the VSS is working and making its way on to the cluster. The odometer / trip meter drive circuit that accepts the VSS signal also provides a signal to the speedometer drive circuit so something has failed in the odometer drive circuit - speedo drive connection or the speedometer drive circuit or the actual speedometer 'meter'. Unfortunately, you are going to have to remove the cluster to investigate.

I have never had to deal with a cluster problem so cannot provide much direct advice. I think member @Heineken has gone through the cluster rebuild process and may be able to provide advice based upon actual experience. He has developed a cluster calibrator which you will definitely require if you have to go through the capacitor replacement process.
 
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Indeed, the speedometer provides a fixed voltage (5 V) to the VSS which then pulls down this voltage for every pulse created. If the odo and trip meter still works, that signal chain can be considered OK.
If a bump caused the needle to drop it's probably somehow mechanically related. Maybe the screws that connect the gauges to the PCB?

like @Old-Guy mentioned, to analyze the issue further it's required to remove the cluster from the vehicle. You can carefully disassemble the unit and check for issues by following the linked post. Please be very, very careful with the screws that connect the gauges to the PCB - if the attached wires inside the gauge snap you're in a world of pain ..

I'm not sure how familiar you are with electronics but with the screws removed it should be possible to check for continuity at the gauges. The RPM and speed gauges are technically similar so they should behave similar when checked with an Ohm meter. Further analysis whether the driver side on the PCB is fine needs a signal generator or cluster tester to simulate the VSS input.
 
I also vote for the rear screws coming loose. I've installed a cluster with a loose screw and it exhibited similar behavior.

Caution: the rear screws only have to be snug, not tight. DO NOT over tighten or your wallet will ache. Barely tight and stop.

The gauges may not be available new anymore, so you're looking at some serious pain if you damage it.
 
Ill be sure to check the rear screws!.
Im not sure if the issues are related but a few months prior to the speedo going dead, at a stop light i experienced the needle jumping around from 0mph up to 80 mph and back. after moving however the issue never came back
 
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