Speedo wiring

[ndgcpr]

HEy all i have wired a few motors in my time but this is really annoying me. basically a mate of mine has a GZ20 which he put in a 1JZ. I have wired everything fairly easily but am lost on the speedo, its all that needs to be done and i have spent a while trying to work it out. it is clearly a 3 wire speed sensor, and the wire colours are green black and red. I am guessing 12V goes to the red wire and the other 2 run to the dash for the speedo. If i put 12V on the red and try another wire (i forget which one now) then i saw 12V or so, when we started to move it went to 13V. I know that you can't measure this stuff with a multimeter but i thought i would anyway.

i ripped the dash out and there is no obvious wires there. i have noticed that there were 3 wires red, white and purple that seemed to come from the same spot on the dash and went to the plug at the ECU on pins that my diagram said were not there, so i am guessing this may be them, but i have no idea. So is there any way of knowing, testing or finding out how i should wire this.

Thanks.

Oh and buy the way, the motor was put in by some mech who just ripped out all the wiring when he pulled the motor, otherwise it really shouldn't have been a problem as it is still running the stock box. Which annoys me

[o_man_ra23]

If its an auto, then the speed sensor would go to the auto computer, and then up to the dash. Im pretty sure you should have power ground and signal out. If you have an oscilliscope and electric drill (to drive the speedo sensor) then you should be able to find the sensor wire, as it will create a small sinusoidal voltage output between the ground and signal, and signal and power. The power and ground should not give an output. All these tests should be performed with no power going to the sensor.

Try this and see how you go.

Cheers, Owen

[ndgcpr]

hmmm, its a manual (which doesn't make too much difference) and i have no occillascope, although using you theory i should be able to see the voltage change slowly with a multi meter if i move the car slow...

My guess was red = pos, black = neg and green is signal but i have been told many different things, CrUZida feels that its a pos wire and two signals, so i dunno.

[o_man_ra23]

Normally you would think its a red pos wire, then the green is signal pos and black is ground, but goes through and is earthed from the dash. This is going by the international red/black pos neg standard, though I have seen plenty of black positive wires in Toyotas. So... black may be positive from the ig switch, and red n green are the signal pos and neg(respectively more than likely) and the power is earthed through the body.

Maybe try that.

Cheers, Owen

[o_man_ra23]

Oh, and the magnitude of the signal is proportional (to an extent) to the rotational velocity. In english this means that if you rotate slowly for your multimeter, you will get just about nothing out, but you will get a fair bit out when you spin it fast. If you stick your multimeter on AC, then you should be able to find a sweet spot where it goes near 50Hz and you can read with the multimeter.

Cheers, Owen

[ndgcpr]

yeah the non engrish made sense

Thanks

Anyone else got any ideas? Anyone know how to wire the speedo to a GZ/MZ20?

[wilbo666]

I would have though it would have been a square wave output....(optocoupled transistor encoder?)...if I am right it won't matter how fast you turn it, you should be able to see the voltage swing pretty well rail to rail (+12 -> GND) as you slowly turn it around if you have it wired right. The frequency of the square wave output will increase as you turn it faster.

But +12, GND and Signal is what I'd expect!

Cheers
Wilbo

[chris davey]

I know a guy who has just wired a cable speedo to a digital dash if that is of any help. 1jz auto in mx83 cressi.

[SL666]

speedo sensors and speed signal make homer go crazy

[chris davey]

go crazy????

[CrUZida]

Nah, its a +ve with, an earth (that earths through the dash. no idea why) and a signal.

[sideshow]

the early soarers are tricky in the speedo section cause the auto ran off a different loom and ecu

i might be in qld in a month is u want it fioxed

[ndgcpr]

Thanks sideshow, maybe, but what else are you gonna do??? i think your hiding something .

I am gonna have another go next weekend most probably (as it is hard due to him being an hour's drive from me). Its just annoying that i wired the whole motor and one little thing is annoying me.

He does have the old loom lying around i think and last time he came to me and didn't bring it so i may be able to trace and guess what is going on.

One question i do have is that the earth through the dash... That is not required to go through the dash is it?? although i guess i could multimeter the wires to earth and see which wire is earth and i think i found one that provides 12V so hopefully it isn't to hard a job, i really want to get it done...

[ndgcpr]

Ok i finally got up there and fixed the thing, i thought i would add to this post that on this GZ20 the purple wire with a white line, which showed 10-12V when the car was running (any load would drop this voltage) was the signal wire and the black with yellow line wire was used as the earth, i wired the 12V line to the IG switch and it all run nicely, I give this info in hope that it will help someone, i will not be held responsible for someone wiring this up wrong and blowing something up (not that it would happen).

And the signal was a simple square wave which increased frequency with speed, Easy to test with a multimeter.

[GZP51]

thanks for the speedo mate, and some REP for you