Hello all. Firstly I’d like to say thanks for any responses as this is my first post.
Now, my 1996 civic’s speedometer is pinning up to about 180 miles an hour once it starts moving.
I’ve done extensive testing with a multimeter already and am posting because after about a month I still can’t find the culprit. Things to note are that 2 of the 3 alternator wires tested positive for continuity with the vss signal wire. I cut one of the wires from the alternator which now the speedo doesn’t move at all so I’m assuming that wire also provides the power TO the speedo. Also it is on a tucked obd1 conversion harness with a manual d16y7 swap into an auto ex shell.

I’ve tested with 2 different alternators, 3 vss, and 2 speedometer units and circuit boards. Could I rewire the speedo system entirely and run power from the battery in an ignition fuse instead of the alternator’s accessory output?

Thanks.

 

The speed sensor is on the transmission. It could damaged/broken. Also your speedometer could be damaged/broken.

There are also accessory-power ports in your umder-dash fuse box. They are small single pin ports with a copper blade in inside (that easily connects to a female spade pigtail). Some are always powered (memory), some come on with dash lights, some are are only on in the run position. Most are fused, but not all. You should look close at wiring diagrams. It's kinda confusing. Just look for voltage in different key and lighting positions, and find the one you need.

 

Thanks for the reply. I’ve tried it with multiple speed sensors and speedometers already. So I will take a look at those ports and update this tomorrow night.

 

These are the plugs I'm talking about. Not sure what year or car these images are from. Not all these plugs are sub-fused, so add a small in-line fuse just in case. If any of the plugs don't work, then there may be an empty fuse bay that needs a fuse. A continuity test can find the correct bay.

 

Ok, that is the one you’re talking about, I thought so. I’m working on it right now.

 

Update: I changed the speedometers power to an ignition 12v and there is no movement from the speedo when driving. It doesn’t make sense to move forward with rewiring the whole vss signal wire if it’s not moving at all. Any ideas?

 

I would start analyzing the wiring and flow charts in the shop manual. Things like testing for continuity on all sections of wire. I'm not familiar with how the cluster and vss operate so I can't really help more.maybe someone else has some insights.

I can say a lot of sensors use the engine/transmission as ground so make sure all your ground straps are good. There is a big one from the transmission to the frame rail just in front of the passengers side mount.

 

Alright haven’t gotten it figured out but ordered a digital gps speedometer. Will probably just use it for a while.