BOl@$%KS Dead Speedo

[vee8]

Speedo died this morning. No speed, no mileage recording. I presume this is a broken cable and not a sticking mechanism

How easy is it to replace the cable, and what cable will fit assuming this is common with other cars?

Thanks in anticipation.

[markh]

I would of thought it was the speed sensor, they seem to pack up for a pass time

[vee8]

Mmmm. No mechanical cable. I'll have a search for speed sensors.

Thanks Mark

[Paulathome]

Hi,
There is no cable on a Chim its electronic so it sounds like your speed sensor has failed
they are known for being unreliable. (cost around 40 quid)
You could check fuses first, on my Chim the speedo and sensor are on the same fuse as the brake lights and reversing light so check these first.
Also check under the car that the sensor is not covered in road crap and that the gap between the half shaft and sensor tip is about 10 thou' and no more.
You will find the sensor mounted on the diff housing (O/S) it looks like a big brass bolt with a wire coming out of the end. The sensor is triggered by teeth on the half shaft passing the tip of the sensor which is then translated into road speed.

Unfortunately the only way of checking if the sensor is working is to put an oscilloscope
across the output pins and look for a square wave signal which varies with the speed of the
road wheel. (with the ignition turned on)
Hope this is of some help.
Cheers
Paul.

[vee8]

Thanks

I'll jack the car up tomorrow and clean the connections. If this doesn't do it I'll best order a new one from Fernhurst.

[Cider Andy]

vee8 said:

If this doesn't do it I'll best order a new one.

It is often the problem, but I'd want to eliminate the speedo itself first, as this could also be at fault. Had any problems leading up to the failure? Erratic readings often appear before failure.

[vee8]

Cider

Not a dicky bird. I was out driving this morning. Think I did a 3 pt turn when I noticed no action in the odometer department.

[sparkythecat]

When my speedo sensor failed there was no erratic readings. It was reading 50mph when the needle dropped to zero and didn't budge again.

Paulathome's spot on with his advice.

Edited by sparkythecat on Wednesday 27th December 18:43

[barreti]

I'd guess you Chimaera guys have the same system as the Griff so check the fuses.
Yep, the fuses WAY down there in the passenger footwell
I pulled out half the inside of the Griff certain that my speedo failure was a broken wire or something because the other systems were all working.
In complete exasperation a mate checked the fuses and one was ever so slightly broken. Not easy to see with the naked eye either so check with a multimeter - or swap the fuses around in turn to see if the problem moves.

I've now bought some fuses from USA which glow when they've blown - which reminds me of a job I've yet to do !

Good Luck.
IanB

[Jasper Gilder]

THis used to happen on my 4 litre Griff. Five minutes in a lay-by with the engine off and it was fine again. I did hear once of a Chim that wouldn't stop recording - did 50 miles while it was on the jack at a dealer - how scary is that?

[vee8]

Well, I've cleaned the area around the sensor as well as the toothed wheel as best as I could, and applied a good dose of WD40 but no good. The sensor at best will be a bitch to get to from beneath the car so guess I'll leave it to Fernies. Much easier from a ramp I should think.

[vee8]

It's on...No wait off. No on again...

[sparkythecat]

Try re-gapping it. It's not that difficult if you get it up on axle stands. You need to use a feeler gauge to measure the gap accurately. If it's more than 10thou' it needs adjusting.



Slacken off the locknut then cut the cable ties securing the excess wire to the chassis. This will allow you to disconnect the sensor plug. You need to do this to stop the wire twisting as you screw the sensor through the the carrier to adjust the gap.

When you've adjusted the gap - my suggestion is 6 thou', tighten the locknut then reconnect the plug and secure the wire to chassis.

This is what the sensor looks like