Speedo not working. Place your bets!

[Tyre Tread]

Over the winter the chim has been off he road and I've done a few little jobs including replacing the driveshaft boots, taking the dash out and relocating the ECU and preparing for the battery relocate (when I get the cables).

I went for a quick spin today just to get the smile muscles working and the speedo isn't working.

I'm hoping its something silly but am open to offer of advice and the best way to approach the problem.

Could it just be grease from the refitting of the driveshaft or is it more likely I've disturbed a connection?

[locodude]

Probably the speedo sender on the back axle, they have to be very close to the teeth to work and when they get covered in crud it turns into grinding paste and wears the face of the sender away. You may be lucky, give it a good clean and fingers crossed.

[andy-w]

Tyre Tread said:

I've done a few little jobs, taking the dash out

my money is you have disturbed somethng here... !

[Blues]

Transducer check the gap

[Tyre Tread]

Blues said:

Transducer check the gap

Right, just had the car in the air and there was some grease around the transducer. Sprayed it liberally with brake cleaner and removed all grease and muck but still not working.

Nothing had been deliberately disturbed around the transducer and I didn't do anything on the side of the dash with the instruments so its a bit of a mystery.

WRT the transducer gap, is it a case of using a feeler gauge and taking the gap down to 10 Thou?

[Blues]

Tyre Tread said:

Right, just had the car in the air and there was some grease around the transducer. Sprayed it liberally with brake cleaner and removed all grease and muck but still not working.

Nothing had been deliberately disturbed around the transducer and I didn't do anything on the side of the dash with the instruments so its a bit of a mystery.

WRT the transducer gap, is it a case of using a feeler gauge and taking the gap down to 10 Thou?

Yes. I can't remember the gap, but it's in the bible. Alternatively, it may have just "blown". On both occasions I have had to replace mine, it started with the speedo behaving erratically, then eventually gave up. I just had another one last month, about £75 ish from Racing Green iirc. Check the wiring from the transducer first. There is a connector about 9" away from the unit. Has this become dislodged during your work? Good luck

[Tyre Tread]

Blues said:

Yes. I can't remember the gap, but it's in the bible. Alternatively, it may have just "blown". On both occasions I have had to replace mine, it started with the speedo behaving erratically, then eventually gave up. I just had another one last month, about £75 ish from Racing Green iirc. Check the wiring from the transducer first. There is a connector about 9" away from the unit. Has this become dislodged during your work? Good luck

Thanks Blues.

I have cleaned the sensor in situ and the wheel and have gapped the transducer from being over 25 thou down to about 6 thou.

The speedo was working pretty well before although for the last year or more it did occasionally drop to zero momentarily (more of a twitch) while on the move at any speed.

I'm pretty sure I didn't dislodge the transducer connector and it looks OK.

I suppose the next step is to remove the dash......again. I have big clumsy arthritic hands so its no fun.

Fibregalss rash here we come!


I suppose next thing to do is

[shpub]

It can also be caused by run out on the trigger wheel causing a tooth to hit the transducer and take it out. If this happening then you'll be replacing the sensor on a very regular basis!

Happened to me with the LS Cerbera so I developed a more intelligent solution that uses a sensor with a built in diagnostic LED and a gap of 1-2mm. There is built in diagnostics to check the speedo as well.

[Tyre Tread]

shpub said:

It can also be caused by run out on the trigger wheel causing a tooth to hit the transducer and take it out. If this happening then you'll be replacing the sensor on a very regular basis!

Happened to me with the LS Cerbera so I developed a more intelligent solution that uses a sensor with a built in diagnostic LED and a gap of 1-2mm. There is built in diagnostics to check the speedo as well.

I've seen this Steve and if its nothing obvious behind the dash its probably the route I will follow.

As I just said above (we cross posted) there was a good old gap and the speedo was working in October and the car hadn't moved so unlikely to have been run out of the sensor wheel.

Edited by Tyre Tread on Sunday 3rd April 13:32

[Tyre Tread]

Nothing untoward behind the dash.

Oh well, looks like you'll be getting some more money off me Mr Heath. Cheaper and moore fun than a garage though!

[Tyre Tread]

Tyre Tread said:

Nothing untoward behind the dash.

Oh well, looks like you'll be getting some more money off me Mr Heath. Cheaper and moore fun than a garage though!

SH speedo sensor ordered.

Anyone else fitted one?

[pbaker43]

I fitted a SH transducer last month due to the same problem the speedo needle was like the ‘durcell bunny on speed’ then it stopped moving all together, when I took the old unit out the front face of the transducer had a nice groove cut into it, as mentioned on the thread I think is due to ‘run out’ and the fine tolerance. To fit the head unit 20 minuets and the transducer 40mins. For some reason I had to space off Steve's mounting plate even with the sensor on the minimum it hit the toothed wheel so I placed two washers under the bracket, after no problem.
Had some fun setting the distance up on the new sensor, mainly due to the limited space for your hands, but now every thing is working, even the oddmeter has decided to work again..