Calling electronics experts

[Russ]

I hope this has worked ,Ive attached a file of a circuit diagram that I hope will reduce the signal to the speedo on a maestro digital dash.It looks like it can be calibrated as it has a variable resistor (is this a petentionometer?)
As ive said in another post im waiting for the fast check solid state instument tester to turn up so I may be able to sort things before fitting to car.

Cheers

Russ

[E_T_V]

Hmm it may work but it might not be very robust, i.e. it may not work at all road speeds.

The fastcheck just checks stuff it doesn't allow you to alter anything.

Find out what the voltage on the input wires for the digi speedo sender. With a volt meter I'm sure you can work out how the speedo sender works and thus be able to use one from a rover 800 etc.

The more robust electronic solution is to use a divider type circuit (there is one on here somewhere for makeing a diesel revcounter work which divides the signal by 8).

[Russ]

Looking at the efi wiring diagram it appears that the speed transducer is fed by battery voltage. The thing that worries me with the 800 unit is that is has an earth.Im not sure if its there for screening as the diesel doesnt (but i havnt found one of those)
But according to the ARG manual the Road speed transducer ,should when connected to an ohmmeter pulse when rotated,the rover one doesnt.
Do you know if the rover one has been known to work the maestro dash ok?

Russ

[Russ]

That revcounter circuit appears to have been deleted,found the link but it no longer works.

Russ

[Guest]

Does this help

[Russ]

Thanks for that,Im wondering whats inside the 'normal' efi transducer (the one which makes the speedo read double) and if the frequency can be halved as ive been told it could be a revoling disc with either cut outs or back/white segments.

Cheers

Russ

[Russ]

sucess Tried the 820 transducer without the earth connected and it works reads 3-4mph high but I think a lot of speedos do. If earth is connected is doesnt work.
Now just got to sort out a few wiring gremlins like the handbrake lights and connect up the trip computer to the ecu.

Russ

[B18 GPC]

Does this help

Ive a stro and monty book.. with loads of old school diagrams etc in , from work... same font as that..

"Service" guidey things? from maindealers

[threelitre]

Doesn't the fuel ECU now get the wrong speed from the transducer?

Regards,
Alexander

[Russ]

[QUOTE=threelitre]Doesn't the fuel ECU now get the wrong speed from the transducer?

The ecu only really need to know whether or not the vehicle is moving,so it can stabilise idle.If anything with the new setup it seems a bit smoother.If I have any trouble with it I will install the frequency divider and go back to the old speed transducer.

Russ

[Guest]

Yeah those are the ones Graham, got it from a Maestro product training book from 1983 when they first came out. Have got quite a lot of maestro manuals collected from ebay and the company i used to work for. (only the stuff they didnt need though)

[Russ]

Been out on quiet roads with road angel ,the speedo is exactly 10% high,im wondering do 220/420s have electronic speedos? As the overall wheel size on these are pretty simillar to the maestro ie 185/55r15 where as the 800s are on 15s with tractor tyres.

Cheers

Russ

[threelitre]

Seems about right for a Maestro My father's Montego reads about 10% high, my Maestro is even worse (being a 1.3 it will run up to an indicated 110mph)...

Our 216 has a speedo cable, but that does not say too much about 420s I guess.

Alexander

[Guest]

I have had a look on MG Rover EPC 2007, and i am afraid that the only cars listed with speedo transducers are and PG1 gearboxes are

Rover 800 T series, with you are having probs with (YBE100520)
Rover 600 T series turbo, (YBE100520)

The Rover 200/400 with the PG1 all had ABS so the speedo was read from the ABS ECU. They list speedo transducers only for the 211 and 214 without ABS, but these use the IB5 gearbox.

[Guest]

10% out is right for every Maestro and Montego I've ever come across!