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[chrisdb]

Anyone got ideas on what might cause this:-

This morning when I started the engine the speedo needle was rapidly twiching beyween 0-2mph. This carried on for about 15 seconds after I turned off the engine. When I drive the speedo seems to get stuck at 40mph - I drive mostly motorway and as I slow down the speedo needle drops slightly, say down to 20mph. When I'm idling the twiching starts again.

I'm hoping it is the speedo because I can change this very easily, but any ideas welcome.

Chris

[Marks DTM Calib]

First thing to do is to press the speedo when it occurs in case the connector behind is not fully home.

Any other gauges causing problems?

Any other fault lights?

[chrisdb]

Right then! I think I've worked out what is happening - but not why :-? Since yesterday I've driven for about 6 hours with stops etc where the engine was turned off. I get a combination of these things...

When ignition turned on the speedo needle vibrates very quickly between -1 and -2 mph. Sometimes it will stop after 30-40 seconds and sit exactly over 0mph. Other times it does not stop until I start driving.

Once driving I get speed readings varying between +/- 10mph, and at times the needle does not seem to be able to go past 40mph. For one stretch last night (about 50 miles) the speedo stayed in the "vibrating" state and the rev counter did not move at all. Most of the time the rev counter "seems" to be working OK.

What it looks like is that the speedo is continually recalibrating itself giving the different spped readings in relation to the true speed. I'm measuring my speed against the satnav which normally would show the speedo to be a few mph behind.

I'm guessing that there is a speed sender somewhere but I have not found it yet.

[TheBoy]

Right then! I think I've worked out what is happening - but not why :-? Since yesterday I've driven for about 6 hours with stops etc where the engine was turned off. I get a combination of these things...

When ignition turned on the speedo needle vibrates very quickly between -1 and -2 mph. Sometimes it will stop after 30-40 seconds and sit exactly over 0mph. Other times it does not stop until I start driving.

Once driving I get speed readings varying between +/- 10mph, and at times the needle does not seem to be able to go past 40mph. For one stretch last night (about 50 miles) the speedo stayed in the "vibrating" state and the rev counter did not move at all. Most of the time the rev counter "seems" to be working OK.

What it looks like is that the speedo is continually recalibrating itself giving the different spped readings in relation to the true speed. I'm measuring my speed against the satnav which normally would show the speedo to be a few mph behind.

I'm guessing that there is a speed sender somewhere but I have not found it yet.

Speed signal comes from ABS. ABS ECUs can be a problem, but this tends to bring on ABS/TC lights, and make steering go heavy.

Thinking panel, or its connection...

[chrisdb]

Right then! I think I've worked out what is happening - but not why :-? Since yesterday I've driven for about 6 hours with stops etc where the engine was turned off. I get a combination of these things...

When ignition turned on the speedo needle vibrates very quickly between -1 and -2 mph. Sometimes it will stop after 30-40 seconds and sit exactly over 0mph. Other times it does not stop until I start driving.

Once driving I get speed readings varying between +/- 10mph, and at times the needle does not seem to be able to go past 40mph. For one stretch last night (about 50 miles) the speedo stayed in the "vibrating" state and the rev counter did not move at all. Most of the time the rev counter "seems" to be working OK.

What it looks like is that the speedo is continually recalibrating itself giving the different spped readings in relation to the true speed. I'm measuring my speed against the satnav which normally would show the speedo to be a few mph behind.

I'm guessing that there is a speed sender somewhere but I have not found it yet.

Speed signal comes from ABS. ABS ECUs can be a problem, but this tends to bring on ABS/TC lights, and make steering go heavy.

Thinking panel, or its connection...

Thanks. I'll get it out over the weekend. Do you think it could also be the speedo itself? I should be able to get a second hand one without too much trouble...

[TheBoy]

Yes, that what I meant by the panel. Or its connection!

Post 98 instruments, as well as the 4 different hardware types, also have different programming via tech2.

Pre 98 instruments are NOT compatible.