SV150 Speedo dead

[jeffi]

My SV150 has had a PBC and awaiting IVA, but the speedo has packed up and I think I need a working one for the IVA. The needle doesn't move and the LCD has nothing displayed on it - it had a zero when I first connected the battery and tested the electric's. I've tried re-seating the connector on the rear; checked the speed sensor is 1mm from the cog, and tried holding the odometer reset button on for 5 seconds when the ignition is turned on. Also had another ECU handy and tried that in case the speedo signal was linked to the ECU.

 

Any ideas what to check next otherwise its looking like a call to CC for a replacement. It lights up when the headlamps are on though!

 

Jeff

 

 

 

[Z3MCJez]

1mm is *WAY* too far (I know that's what the build manual says ). Try moving it to within 0.02mm at the closest point (the gap will vary as it won't be completely true) and try again.

 

Jez

[Garth]

You will need a working (and accurate) speedo for your IVA

Our speed sensor is 1mm away from the 'disc' and it works fine.

Sounds like there is a problem with the instrument.

Try this..Switch the ignition off, then press the button and hold it down while you switch the ignition back on. Within a couple of seconds you should get a 6 digit number appearing which is the speedo input code. this will at least tell you if there is some life in the speedo unit!

The illumination is a separate circuit?

Good luck and let us know how you get on

 

atlast

[jeffi]

Hi Garth - I tried holding the button in but sadly it did do anything. Also, just noticed that the needle is stuck on about 12mph and not the rest point, so the stepper motor seems to have stuck. The dial illumination is on one of the pins. So much for British (or Welsh) engineering!

[John Cockburn]

Hi, have you tried the instrument fuse? I had a speedo stuck on 40mph (Sigma 150 SV 2008) and it turned out to be a 10amp fuse (2nd from left), worth checking.

 

Cheers John

[Z3MCJez]

Speedo sensor failure leads to blown fuse. If nothing is done that also leads to dead engine pretty quickly as it blows two other fuses. Has happened to a number of us with Sigma engined race cars.

 

If replacing the fuse resets the needle, I suspect you need a new sensor. I've actually now removed the speedo sensor, but I appreciate that's not practical for a road car and will not pass IVA.

 

Jez

[jeffi]

Joh, Jez - all the fuses are good. I'll pop the car onto axle stands and check the output from the speed sensor with the ignition on (engine not running) whilst turning the hub, so the toothed cog passes over the sensor. This should prove whether the Hall effect sensor or the head unit (speedo) is at fault, or potentially a wiring issue in between.

[Pete-B]

Jeffi,

I've had to change the wheel sensor twice on my Sigma. theres no need to switch on the ignition to check, just jack the car up and turn the wheel if the sensor is alright you will see the light come on each time one of the cogs passes it. If the light doesn't come on try cleaning the contacts then adjusting the gap, this sometimes works.

 

Best of luck.

 

Peter

 

PS The gap on mine is set at 1mm and works fine, any closer and it dosen't work, I guess that part is trial and error. If it is the sensor ring CC and they will send you a replacement.

 

Edited by - Pete-B on 11 Jul 2010 19:06:13

[Garth]

Peter, where is the light you are referring to?

 

Garth

 

atlast

[Pete-B]

Garth,

 

It's on the sensor itself, it lights up each time one of the teeth on the disc passes it.

 

 

Peter

 

Edited by - Pete-B on 11 Jul 2010 20:52:42

[jeffi]

Pete - good test. The end of the sensor where the lead emerges is a clear plastic about 2-3mm thick and this must be an LED as it does indeed light up yellow and flash as the hub is rotated. I have to have the ignition on though (engine not running). It's flashes for each tooth going past, and it may or may not be lit when you stop rotating the hub depending where it stops, but a slight movement will make this change, so this proves the sensor is fine, thx.

 

I'll check the signal is getting to the speedo plug to eliminate the loom.

 

Jeff

[jeffi]

The replacement speedo arrived from CC this week and I fitted it yesterday. The LCD display a zero for the mileage and when I turn the rear RHS hub with the sensor, the needle moves, albeit only a little, so it looks like it's fine now. I won't know for sure until I drive it to the IVA but I will ask CC is I need to calibrate it - but I hope they sent out a unit already setup. I'll compare it to the sat nav reading..

[Garth]

Jeff - I have sent you mail - I could send you the speedo input codes - you could then make sure yours is correct. When I did my IVA I had to change mine alot as I suspect they had a problem with there calibration equipment! On the way home it was over reading by about 20% compared to my sat nav! I just changed it back to the CC code and it is much closer to what my sat nav is telling me now!

 

Garth

 

atlast