Hi all,

Does anybody know what voltage would be generated by the transducer on a refurbished RML?

Im guessing its small, I have a gear fault which is only giving 1/2/R and no 3rd and in 4th it seems to stay in second.

Any advice gratefully received!

Dunno, but check the air supply to the different gears by taking off the EP block cover and putting 24v to each of the contacts. I think the rearmost contact is negative. Disconnect each air pipe at the gearbox end to check air comes out. It could be the control board is defective.

My bus number (if any): RML2532 GS67 BEA MLL721 BEA MLL738 RT2629

Hi David

I have one in stock if you whant to try it ???
whats the speedo showing is it dropping off, if so that can give you a problem with the gears.
email me or call
Martin

My bus number (if any): RML2683

The signal from the sensor varies in amplitude and modulation with the speed of the bus.This can be from 0v to an potentially infinate maximum but in practice is never more the 5v peak to peak RMS.Don't forget it gives an equal negative signal as well depending on where you measure your 0 volt reference point from.This is why the signal is fed through the 551 panel to convert it into something the speedo can interpret.Try fitting a by pass plug to see if you then can get the gears.Also check the reading through the connections on the small plug on the panel to see if you have a circuit.A small resistance should be present,if not you have a wiring problem which is quite common.

My bus number (if any): RML2551

Hi Everybody,

Thanks for all your replies.

So far we have

Tried a bypass plug which gives us all gears.

We have also tried another 551 unit and have the exact same symptoms.

Next thing is to check the cable for resistance so its either that or the transducer!

One thing that popped into my head was that the transducer generates a pulse for the 551 which it uses for info on road speed for the gear changes and the signal for the speedo. Am I right in saying it generates its own power?

If so when stopped the prop doesn't turn so it can't be sending a signal?

When the bus is stopped we have 1/2/R and in 4th it appears to be in 2nd, with nothing in 3rd!

I may be misunderstanding your description, but:

Everything is working correctly if with the 551 panel connected you can't select 3rd gear if the bus is stationary. It will also select 2nd gear when the lever is in 4th position.

If however it does not change automatically 2,3,4 and 4,3,2 with the panel connected and the lever in 4 - then you have a fault.

Likewise, again with the panel connected, if you cannot manually select all 4 gears when moving at an appropriate speed - then there is a fault.

If you start in 2 and move the lever to 4 you may well not trigger a gearchange until the panel decides that the appropriate speed has been reached.

If you are at the wrong speed when manually changing from 3 to 4 then the panel will revert to the original gear immediately.

On some buses if the vehicle is stationary with the handbrake applied and the bus in 4 the panel will select neutral after several seconds, but the lever will remain in 4. Again this is correct.

David ,
going back to your first post and Roy's last reply . The symptoms you described if the bus is stationary is correct- nothing is wrong . However , if the bus is moving and you cannot get 3rd and get 2nd in 4th then you do have a problem .
Using a bypass switch will select all gears when stationary . The RM does have protection to prevent use of the wrong gears at the wrong speed , using a bypass plug removes this protection . Does the bus drive ok either auto or semi auto ?
mark

My bus number (if any): RML2391

It appears the transducer was at fault, it was replaced with a radionics unit with success.

Thanks for all your help.

Hi David - could you let us know the details of the "radionics unit" please in case anyone else should need one in future?

My bus number (if any): RML2302

This is the link, I believe the original type is no longer available.

http://uk.rs-online.com/web/p/magnetic-pickups/0285762/