The V8 Owners Forum -

Hi there,

Question, because my mate has no clue and I'm an electronic idiot too:

he has a electronic Autometer speedo connected to the Rover SD1 auto box. The needle swings from left to right and it seems that something is not working right. Is there a need for a special adapter etc.

Kind regards
Pitschi

Presumably autometer will want a specific type of signal fed into it. What do the instructions say ?

The SD1 speedo sensor is active - it contains electronics, rather than just being a simple generator. Maybe a type of hall effect. One side is connected to +12v - the other to the speedo. So may need the correct load (to ground) to work properly.

We have 2 cables from the gear box. One we connected to the speedo, one to ground. The cable from the speedo to +12V.

Before anything else, are you sure the gearbox sender is good? I'm on the 4th on my SD1.

Next I'd ask Automotive if they know this combination.

If not, I'd try a 1000 ohm resistor between the speedo input (sensor output) wire and ground.

We will try Dave, Thanks

Pitschi wrote:We have 2 cables from the gear box. One we connected to the speedo, one to ground. The cable from the speedo to +12V.

So have you connected the signal wire to 12v also.? The speedo unit has it's own 12v supply terminal.

I think you should try a 12v supply to the sender as per normal sdi wiring ( usually a white wire) and the other sender wire to the speedo signal terminal.

Most 2 wire sensors will generate their own voltage.

Sometimes the device this is connected to will be polarity sensitive, sometimes not.

Generally 3 wire are hall effect and require a voltage supply. ie 5-12v ground and a signal wire.

really you need to know what the speedo wants to see then you can set about achieving it

stevieturbo wrote:Most 2 wire sensors will generate their own voltage.

Sometimes the device this is connected to will be polarity sensitive, sometimes not.

Generally 3 wire are hall effect and require a voltage supply. ie 5-12v ground and a signal wire.

really you need to know what the speedo wants to see then you can set about achieving it

I have the wiring diagram for the SD1 and that shows a 12v feed to the sender. Maybe the body of the sender is the third wire, ie earth.
Regards Denis

DEVONMAN wrote:

stevieturbo wrote:Most 2 wire sensors will generate their own voltage.

Sometimes the device this is connected to will be polarity sensitive, sometimes not.

Generally 3 wire are hall effect and require a voltage supply. ie 5-12v ground and a signal wire.

really you need to know what the speedo wants to see then you can set about achieving it

I have the wiring diagram for the SD1 and that shows a 12v feed to the sender. Maybe the body of the sender is the third wire, ie earth.
Regards Denis

Very possible, or the sender itself might be a more basic on/off mechanical switch inside as opposed to a more fancy electronic item

As far as I know the SD1 sensor has electronics inside it - ie transistors etc that require a power supply. I'd guess this is to generate a near constant level square wave pulse - a simple alternator would produce a sine wave of varying voltage which would be more difficult to detect.

It's of a sealed construction, so difficult to get inside it to be sure.

I'll try to get the instruction papers and what exactly the speedo number is.

Will give you an update. Thanks anyway.

Cheers
Pitschi

I have an electric Autometer speedo together with LT77 box. I used a broken LT 77 sender and made an adapter to physically connect it to a Autometer sender. AFAIK all Autometer electric speedos have the same internals so any instruction will be OK.

http://www.autometer.com/resources/index/faq_view/id/36

" I used a broken LT 77 sender and made an adapter to physically connect it to a Autometer sender"

How can that be done?

Didi you use http://www.autometer.com/hall-effect-sp ... ender.html

or http://www.autometer.com/hall-effect-sp ... ug-in.html

Cheers
Pitschi

I have the ATM-5291 version.

I did the conversion over 10 years ago and had to really think back how it was done. I machined a new speedo housing/bearing ( http://www.rimmerbros.co.uk/Item--i-22G1486U ) with a threaded boss for the Autometer sender. My box was a mechanical speedo version so I used a sppedo drive pinion from that box.

I think I have a scrap sender for SD1 box somewhere. I have to check if I can find it and see how that can be modified.