Flexer

Is there anyway I could test if my speedometer is working?

To get right to the point is there any way on an EG civic speedometer to the speedo needle to jump around with a AAA battery or 9v battery something just to see that the speedo is getting a good signal and the wiring is good. I just took it apart and re-soldered all the joints.

Former User

The speedometer supplies a reference 5V-10V to the VSS. The VSS supplies a pulsing ground to the speedometer voltage. The speedometer converts the ground pulse rate it detects from the VSS to mph/kph.

Flexer

If it is pulsed I would assume as the pulses increase the speedo goes higher and higher.......so what if a constant 5v was supplied to the speedo? Should it then peg itself all the way around and max out?

Former User

You have it reversed. The speedo supplies voltage rather than receives it. You need to supply power to the speedometer so that it can send voltage to the signal wire. If you now provide a pulsing ground to the signal wire, the needle should move.

Flexer

Gotcha. So if I ground the signal wire will that peg the speedo to at least make sure the needle is working and everything, or is fully grounded "0 MPH" and as the pulsing goes from slow to fast that is what moves it up? meaning I would have to have someway of faking a rapid pulsed ground.

Former User

No. Grounding is the mph signal - slow ground pulse = low speed/mph, fast ground pulse = high speed/mph