Speedometer Running Backwards

[Dannguyen124]

Hey guys I have taken a look around the forums and haven’t been able to find a clear / definite solution to my problem.

Background:
I have a 92 S13 Vert.
Ka24DE
Manual swapped before I bought it

Problem:
My speedometer is pinned to the right. When I speed up to around 30 mph, I noticed that the needle will start to move but in the wrong direction (counter clockwise). However, my odometer works correctly.

I read around that it may be a bad speedo? Is there anyway to fix the speedo without buying a new one by soldering? I don’t really want to spend money on a new speedo right now. Eventually in the future however I would like to upgrade my gauges to the NX Digital Cluster and was wondering if I replace the gauges with a digital one would it have the same issue.

[VStar650CL]

Most of the speedos and tachos in that era used balanced air-coils and not stepper motors, and what you're describing sounds like a low side coil with a crappy ground. It won't be a problem with the VSS because the car would be throwing codes, so whatever the problem is, it's almost certainly internal to the cluster. If you're handy, pop the cluster apart and look for degraded solder joints on the mainboard. Refreshing the solder connections will often fix up that sort of issue.

[Dannguyen124]

Most of the speedos and tachos in that era used balanced air-coils and not stepper motors, and what you're describing sounds like a low side coil with a crappy ground. It won't be a problem with the VSS because the car would be throwing codes, so whatever the problem is, it's almost certainly internal to the cluster. If you're handy, pop the cluster apart and look for degraded solder joints on the mainboard. Refreshing the solder connections will often fix up that sort of issue.

Ok, I will take my cluster out this weekend to check for degraded solder joints. Thank you for your response. I will give an update if anything changes.

[PapaSmurf2k3]

Subscribing.
I've got a wonky speedo right now too. It likes to peg itself out sometimes. Other times it doesn't read at all, and other times it reads 1/4 to 1/2 speed

[VStar650CL]

I've got a wonky speedo right now too. It likes to peg itself out sometimes. Other times it doesn't read at all, and other times it reads 1/4 to 1/2 speed

If it's your 240SX, then same advice. I've probably fixed dozens of '80's~'90's clusters for various customers and there are 3 things that go wrong, broken solder joints, corroded copper traces on the mainboard, or broken traces on the flex-board for clusters that use them. Aside from blown and leaking capacitors (which are usually obvious), I've rarely seen actual chip or hardware failures. First thing to try is "freshening" all the solder joints by re-melting them with a dab of new rosin-core solder. If that doesn't work then take an ohmmeter to the traces, solder on jumper wires to reconnect any broken ones.

Cap failures are most common on vacuum fluorescent (VFD) cluster displays, but if you do notice any leaky caps, those are easily replaced. Just read the value and voltage off the side of the old cap and locate a replacement at Mouser or Digi-Key. With values below 10 microfarad (uF), with some fancy soldering you can often replace them with a ceramic surface-mount part that won't ever leak again.

One last thing that happens occasionally (especially to flex-boards) is diode failure, since many of them have diodes soldered right to the flex copper. When the solder connections go bad, the bouncing can cause the diode to fail too. They're simple to test, put your ohmmeter on "diode check" and put red/black on each side of the diode in turn. You should get infinity in one direction, non-infinity in the other. If you get infinity both ways then the diode is failed open, if you get a reading both ways then it's melted short. Plain old 1N4001's from eBay will fix them right up.

[PapaSmurf2k3]

It makes sense. My odometer gears are also toast, so I wouldn't mind sourcing another gauge cluster or something instead of attempting to fix the broken one... unless you've got a line on some replacement gears as well

Here's a not-so-great video about the speedo replacement. Lots of fluff in the video but if you skip around, you can get the gist of it.