Help with speedo pinout!

[Daniel Escobar]

Can someone point me in the direction of this speedo pinout?

 

Bought used and can't seem to make it work. I found a pinout online, but not sure it's the same... (But pin 1/5/8 match the pinout) I have tested pin 6/7 and even 3 for the speedo signal, and no movement at all. Speedo boots and sweeps the needle OK, I can set the PPU, but it won't move at all. Also tried Drive PPU, but won't move either.  

 

When sensor is on tooth it registers 0.6V on the pin that gets to the speedo and 0v when not on tooth. 

 

- speedo sensor light up on every tooth

- 1K resistor is in place between pin 1 and speedo wire (currently pin 7)

- ground is to chasis

 

Not sure what else to try....

 

Thanks!!

[MV8]

Are you replacing a speedo that stopped working or retrofitting?

I don't know why you would check pin 3 or 6 when the input is on pin 7.

Put it on stands so the rear wheels can turn for testing (no need to spin faster than idle in first), then input PPU half of what you calculated, then drop by a thousand until you get an indication. 1000 ppm with no indication and the gauge is likely junk.

 

 

 

[Daniel Escobar]

Thanks. 

 

I'm retrofiting one. mine was a racecar and did not come with speedo. 

 

I tested 3/6 because that pinout shows it's also a input, but there are so many speedo variants...

 

I have tested each pin, the car on stands and the needle won't move. 

 

Speedo sweeps the needle and lights up, I can enter the ppu menu and setup

 

Will try with a very low ppu to see if it moves at all....

[MV8]

It sounds like you grounded then applied power to pin 3 and 6. It's possible damage occurred to the gauge if you did this to pin 6. Good luck.

[Daniel Escobar]

The original PIN with the oem harness from a 420R, was 7. and it didnt work, so tried 3/6 to test. just set 1000 as de PPU and no luck. Still unsure if 0.6V is the correct voltage for the pulses... 

[MV8]

Are you saying the retrofit is only the speedo, reusing your existing speed sensor? What kind of sensor do you have?

[Daniel Escobar]

Nono, my car is 2015 R300 Racecar, that had no speedo at all. I bough a full set of used gauges, a new 420 wiring harness and speed sensor. Retrofitted everything. I using the latest speed sensor (the one that has the led): https://caterhamparts.co.uk/senders/6707-rear-wheel-speed-sensor-kit-de-dion-cars.html

 

The 420 OEM harness indeed used pin 7 as the input on the speedo connector, but out of the box, it didn't work. That why I tried 3/6.

 

 

[MV8]

I THINK you need to jumper pin one to pin three. It depends on the sensor type (NPN or PNP). Based on the harness resistor connections, it looks to be NPN. It is either ground or power to pin 3. I take no responsibility! Good luck.

Edited June 9, 2025 by MV8

[Daniel Escobar]

Thanks! cant believe didn't read that footnote that mentioned about the red wire. Mine is NPN, so will test adding 12V to pin 3 with the load resistor