MZ11/MA61 Digital Dash issues! HALP!

[Admiral coFF33]

but i cant connect it to loom
and reach the 3 pins


Ie. cannot physically do this as there is no space

[JustCallMeOrlando]

I think what he means is find the actual power wires for the dash on your 81, so you know what to connect on the dash for testing.

[toyoda]

or just run three wires into an area you can reach !

[Viper]

When I pulled mine out to work out the pulses, my unit had the connections written on the PCB.
You need to power the bugger for it to work, otherwise you get nothing.

Its +5v I think, but +12 cont damage anything, it just makes the pulses bigger.

From memory its was
Red = +
Yellow = Gnd
Blue = Signal

But don't hold me to that. Examine the PCB and look for a little + and - next to the solder points.


Oh, and to your problem, I'd say its a loose solder joint which heats up in the 'hotter' temp and leaves you with no signal to the digital dash.
The odo is gear driven, so if you have drive, they will move.

[StuC]

im with Viper. sounds like dried solder joints to me. My r31 ECU did the same thing. shit running when cold, fine when hot. Went over an re-soldered the tracks and worked a treat

[takai]

You wont be able to detect the pulses on a DMM, youll need an oscilloscope.

Will check in the morning, have an essay to write now.

[Sammich]

im getting this same issue on my MA61 dash...it seems to read fine for the first few minutes of driving, but after that the speedo reads less and less and eventually just sits on 0. possibly related is my fuel gauge which seems to read mostly empty as well (yes I filled it up )

gonna take the dash out when I get the car home next and see what I can see...but im in the same boat as Coff when it comes to electronics no effin clue lol

[Viper]

K, I was way wrong with my colours.

Got the sender in my hand now.
Yellow = +5/12
Blue = Gnd
Green = Signal

(I had attached 3 other wires to read off, Red, Blue, Orange... so that's what got me )

And yes, def. need an oscilloscope to see the square wave. Unless you have a frequency mode on the multimeter....

[takai]

Yeah, definately Yellow 12v, Blue Gnd, and Green Signal.

I have the opto board on my desk atm.

[toyoda]

So if Viper is correct and it is square wave it is probably a Magnetic Resistance Element and the Sine wave signals are fed into a Comparator to change them into a Digital on/off.

So there should be a 5volt input.

Doesnt help you much though !

[takai]

Its an optical hall effect sensor.

[toyoda]

Erm, If its Optical it isnt Hall effect !

Optical has a shutter wheel that blocks off light being shone on to a Photo Transistor
Hall effect waves Magnets over a Hall sansor
MRE waves magnets over a series of coils

[RyleyMA61]

in the abscence of cool1, may i say, bad earth?

[takai]

Sorry, pre-morning coffee. Optical square wave is what i was looking for. I.e. latching on shutter. My bodgyarse USB Oscilloscope says that its not a complete square wave, but its basically good enough. takes about 1/25th of the square period to latch on and off.

[Admiral coFF33]

ok thanks guys thats an awesome help

now in regards to the 1984 hall sensor.

what wires would we think these are?

Yellow: 12v?
Red signal ?????
Blue GND ??????/