electronic speedo in early dash, any advice please?

[heckflosse]

Hi everyone,
I have tried to convert our 79 early dash 265 to electric speedo .This involved fitting the head from a 92 245 donor car into the 79 instrument panel.
Im using the whole car loom from the 92 car,mainly for the LH2.4 etc as its now a turbo.
Am I correct in thinking the 3 wires in the L shaped connector that go onto the back of the head are all that s needed?
I have ign live on the blue/black wire, earth on the black and continuity on the green/white that goes to the diff sensor.
Jacking up a wheel and running it in gear doesn't make the needle twitch even- am I missing something?
The speedo head has 4 "prongs" which obviously connect with the later printed circuit. Something to do with Cruise control perhaps? These are not connected to anything on the 79 car.
Looking for clear info on Turbobricks has as always left me rather puzzled.
Thanks,
Jim

[Bugjam1999]

Hi,

This should help-

http://cleanflametrap.com/speedoDiag.html

Perhaps you haven’t bridged the two pins, as detailed in the linked guide?

I’ve done quite a lot of research into the speedo conversion, so reply if the above guide isn’t enough info.

Note- the three pins, you’ll bridge two to supply 12v to the board. The third, unused pin is the speedo signal that 2.4lh needs to make the idle etc work properly, so you should connect that to pin 34 on the ecu.

Cheers

[heckflosse]

Thanks Sebastian, off out to the freezing garage I go!
Will update later,
Jim

[heckflosse]

Well, ran out of time as usual.
I hadnt bridged the centre two pins, tried that but no difference.
Had voltage up there and the L shape connector is a reasonable fit.
Axle and wiring loom was from a previous car we used for years with no speedo woes.

I have another untouched instrument panel from a mid eighties car, am inclined to try connecting up that three pin circuit board instead of the 4 pin one.
At the moment I will be happy for the speedo to work, recalibrating it can come later.
Will get there eventually, other things to do now so must dash,
Jim

[Bugjam1999]

Try the other dash and see- it might be a conflict with the later abs dash and the wiring for the older dash?

As an aside the tone ring on the diff in an abs car has 48 spaces, the tone ring in a non-abs car has 12, so even if the abs clocks worked the speedo would far from correct.

Cheers

[Clifford Pope]

Once when I had to replace a faulty axle sensor I swapped in a known working spare from a nearly identical model (1993 to 1990) and it didn't work.
I noticed by accident that it did work in reverse, so I simply swapped over the wires to the sensor, and all worked well.

The connector under the boot floor had identical connectors and the wire colours of the two cars were identical, and the connector would only plug in one way round. For some bizarre reason Volvo must have chosen to reverse the polarity of the sensor.
So never assume that identical working components will work when plugged in.
I had exactly the same phenomenom with a tail gate locking solenoid - it worked perfectly, but in the opposite sense. The wiring colours had been changed round at the connector.

[mylittletony]

Originally Posted by heckflosse

I have another untouched instrument panel from a mid eighties car, am inclined to try connecting up that three pin circuit board instead of the 4 pin one.

That's probably a sensible idea. I used an '86 speedo when I did mine

Seb's comment about ABS is also worth noting, an ABS speedo will be expecting 48 counts for one revolution, so you would have to be spinning the rear wheel at 40mph to register 10 on the speedo.

Did you connect the other wire from the sensor to the black earth pin too?

[heckflosse]

Originally Posted by mylittletony

That's probably a sensible idea. I used an '86 speedo when I did mine

Seb's comment about ABS is also worth noting, an ABS speedo will be expecting 48 counts for one revolution, so you would have to be spinning the rear wheel at 40mph to register 10 on the speedo.

Did you connect the other wire from the sensor to the black earth pin too?

I joined the centre two together.
Too busy to look at it for a few days now, grrr

[heckflosse]

The axle is not ABS, Ive never seen a 240 with it fitted.
Can i try a different speedo using just the L shaped connector and bridging the bottom 2 pins as per the link?
The upper pin is the LH one, so run a wire direct to the ECU?
thanks for the advice, chaps.

[Bugjam1999]

Originally Posted by heckflosse

The axle is not ABS, Ive never seen a 240 with it fitted.
Can i try a different speedo using just the L shaped connector and bridging the bottom 2 pins as per the link?
The upper pin is the LH one, so run a wire direct to the ECU?
thanks for the advice, chaps.

Abs was only fitted to very late cars, so it’s quite rare to find a car with it. The speedo you have already tried, with 4 pins, was from an abs car.

Try your other speedo with three pins, connected as you say above.

Cheers