Earthing Straps

Or "borrow" one of the bolts that holds the engine rocker covers on.
Saves a trip to Hell-Frauds and £2.09

Unless the Turbo rocker bolts are longer than the Atmo ones Simon, ...... they are not long enough.

Turbo car rocker cover bolts were long enough for me .
Thanks John, yes the Atmo is a different beast.

My trip to the garage this morning to get the Alp onto their ramp to inspect/test the gearbox sensor has not produced a definitive result as far as I can make out. They inspected the three pin connector and pronounced it ok and checked the seating of the sensor in the gearbox casing which also seems to be as it should be. They achieved a reading of 1.8ohms on terminals b&c which is lower than the anticipated 2.1.
We then jacked the back wheels so that they could run the engine/transmission while stationary but got no current from the sensor.
Does there need to be an independent 12v supply to test the output from the sensor?

Murf.

They achieved a reading of 1.8ohms on terminals b&c which is lower than the anticipated 2.1.

That reading is fine Murf ....... a difference of 0.3 ohms could be the meter leads themselves ...... the main thing is that there is a reasonable resistance across the coil, and it is not shorted to the third pin (a) which is earth, which would kill the signal altogether.

We then jacked the back wheels so that they could run the engine/transmission while stationary but got no current from the sensor.

The problem of using a DVM to "see" a pulse stream, is that DVM's have to sample the signal before it can display a reading and it cannot do that to a stream of fast moving pulses. You really have to use an oscilloscope to view the pulses (see pic below) ....... there is more chance of getting an indication of activity by using an analogue meter, but even then you will not get an accurate value reading.
I hope this is of help to you.

John

Many thanks John that's all very helpful. However it now means there is no alternative but to commence the dismantling of the instrument panel, carefully following your 'speedo fix2' instructions. I've got an eye op scheduled for Monday so unless it gets cancelled again I will be stuck at home unable to drive for a few days so what else could I possibly fill up my day doing!!
I'll post on any further progress.

Murf.

It has occurred to me that the problem might be similar to the one JohnC had with the odometer rotors partially seized in that my odometer is reading 080051 and I wonder if it struggled at the change from 79 to 80000.

There is a test to check the workings of the Speedo motor and that the odometer is not stuck posted in the RAOC Members Area under the title "Speedo Motor and Odometer Test ".
It could be useful if you think one or other has has failed.

I've made slow but steady progress dismantling the instrument binnacle but it's got to the point where I need to detach the speedo / rev counter assembly and it seems reluctant to pull out in spite of removing the four mounting screws.
The main cable cluster which runs over the top is cable tied back. If I cut these ties which are very difficult to reach, will that free it off? The other thing I'm nervous about is the large white connector to the left of the speedo which I've not been able to pull apart. It's mounted on/passes through a metal bracket but I've so far been unable to separate the two.
All this might seem less challenging tomorrow in daylight but I'm concerned about how everything I've so far touched has felt as though it might fracture at any moment. There is also evidence of previous visitors where several plastic tabs have been broken off, the two main sections may have to be taped back together along the bottom edge.
Thanks to Clee's advice over the phone I was able to split the main sections to expose the wiring but the manual I have for the car is very disappointing and lacking in detail.

Murf.

I've made slow but steady progress dismantling the instrument binnacle but it's got to the point where I need to detach the speedo / rev counter assembly and it seems reluctant to pull out in spite of removing the four mounting screws.
The main cable cluster which runs over the top is cable tied back. If I cut these ties which are very difficult to reach, will that free it off?

The cluster of cables that run along the top of the unit should be free from attachment to the unit as this cluster stays on the car once the instruments are removed. So the cable ties will have to be removed, Might I suggest that you take a pic of how the cables lay over the top of the unit before removing them, as they must go back in the same place or you will have difficulty putting the cover back on.

The other thing I'm nervous about is the large white connector to the left of the speedo which I've not been able to pull apart. It's mounted on/passes through a metal bracket but I've so far been unable to separate the two.

This connector can be hard to separate, but this is a good thing as it shows that the connector pins are tight. You might have to grip it tight and rock it to work it loose........ Having done those things, the unit should be free to remove .... but there is another smaller connector behind the unit which will have to be disconnected before the whole unit will be clear. That connector is on flying leads so if you pull the unit forward a bit you will be able to get to it.

John

That's very reassuring, thank you John. I now feel I'm heading in the right direction. Will have another go at it this afternoon trying not to break anything!

Murf.

Bit of a mixed bag in terms of progress today. The good news is that after a lot of wrestling and swearing I managed to extricate the speedo/ rev counter assembly from the main housing and pull it out enough to be able to rotate it (see pic). The large white connector block absolutely refused to split apart so in the end I gave up for fear of causing damage.
I then hooked up a 6v supply to the speedo as per John C's post but there were no signs of life from the needle despite pushing the trip reset several times on the odometer. I assume this means the speedo motor just isn't working.
It was intermittent for a long time before finally packing up last month but I'm not sure where to go from here. Is the drive motor something that could be repaired by a local auto electrician?

Murf.

I then hooked up a 6v supply to the speedo as per John C's post but there were no signs of life from the needle despite pushing the trip reset several times on the odometer. I assume this means the speedo motor just isn't working.

Clearly if you have good connection of the 6v to the red and black wires .... then either the motor has failed or the odometer is jamming, and that will stop the motor.
This seems to be a catastrophic failure and there are two options ..... Either invest in a new complete instrument unit from Stephen, or box yours up and send it to me for checking, but I cannot make any promises that I can repair it, but I am willing to try.
Either way you are going to have to unplug that large connector.
The quickest but most expensive way is a new one, but if you are in no rush for it, then send it to me.
Let me know what you would like to do ...... but do check that your 6v is making good contact with the connectors pins.

John

PS ..... What source of 6v are you using ?

Thank you John for your response and very kind offer. I'm using a new Eveready 6v lantern battery as the source of power and crocodile clips to attach to the red and black pins on the speedo drive block as you suggested in your post. However I'm not convinced that I have good contacts with the existing clips so am planning to get new ones tomorrow when my post-op driving curfew is over and will retest to see if there is a response.
The large terminal block which was giving me trouble yesterday was sprayed with WD40 and after a great deal of wiggling came apart so everything is now a lot easier with the assembly out of the car. I've gently checked the rotors on the odometer which seem free and there is slight movement on the trip rotors when the reset button is pressed.
Will report on any developments.

Murf.

I'm using a new Eveready 6v lantern battery as the source of power and crocodile clips to attach to the red and black pins on the speedo drive block as you suggested in your post. However I'm not convinced that I have good contacts with the existing clips so am planning to get new ones tomorrow

Clearly .... we must ensure that we have exhausted any possibility that the 6v are not getting to the motor. I have used pins really for photographic reasons, but what I would normally do, firstly make sure that the two wires that are connected to the battery are making good contact with the battery terminals, then check the other ends of the two wires have 6v on them with a meter or a 6v bulb from a torch if you have not got a meter. Then I would strip off 5mm of insulation from the two wires ... twist the strands if wire is stranded, and either slide it into the red and black of the smaller speedo connector .... but I would also check by touching the wires into the side of the connector where the barbs are. That way you will be absolutely sure that you are making good contact with the connector pins as you can see the wires are making contact.
It might seem very silly to point out the obvious, but I would be a shame to have to send the unit to me only to find it works straight away. So I apologise for the forgoing sermon.

John

There is a test to check the workings of the Speedo motor and that the odometer is not stuck posted in the RAOC Members Area under the title "Speedo Motor and Odometer Test ".

John, is there a similar process to test the rev counter motor ?

John, is there a similar process to test the rev counter motor ?

Unfortunately not Paul ....... I have experimented using my pulse generator but the maximum pulse voltage it can deliver is only 5v, now as the rev counter on the Atmo counts the pulses from the switched side of the ign coil, those pulses have an amplitude of 12v, so I can only assume that pulses of 5v are insufficient to trigger the rev counter circuit.
As I have not had to test or repair a rev counter, I have not pursued the matter.
Are you having problems, or was it just a matter of interest ?

John