ae85 tacho not working with 4age

[buckas]

Hey everyone. I've tried searching but don't seem to come up with quite the relevant threads. If someone knows this has been covered before please send me in the right direction. I've established that the tacho wont work with standalone aftermarket ecu, but can if modified? Some of the links to how to fix the problems from old threads dont work anymore so I've hit a wall.

I've bought an ae85 with a 4age bigport. It has a motec m4 installed with electronic ignition. Not too sure on the details of the ignition but I'll chuck a couple of engine bay pics in as well.

The tacho doesn't work. I've pulled the dash cluster out and the board is fried where the tacho wires go. My gf's dad is an autosparky and helping me out. Basically what I want to know is if I buy a replacement cluster, can the tacho work? He said it very well may not due to the ignition changed so I wanna know if I'm wasting my money. In which case I'll just buy an aftermarket tacho. This has obviously been done previously and taken out with the wiring behind the dash/holes to mount it. But I'd much rather keep the standard tacho if possible. The wiring behind the dash cluster is getting a signal from the ignition setup.

Also, if it is possible with a new cluster, what needs doing to wire the standard tacho up?

Thanks for any advice and help

[Flush-on-15s]

sorry mate I am no help but I am just gonna say damn that intake D: yummmmm.

[Slimer86]

I am currently in the same boat.
Check the MoTeC forum for m48 tacho fix.
2 methods to try, pull up resistor and the relay coil method.
Unfortunately none of these worked on my ae86 tachometer.
The ecu most probably is outputting a tacho signal from aux 3 or 4.

As a last resort I tried the witzl tacho mod circuit (external circuit) which can be found on Toymods.
This didn't work for me either.

I then modified the tachometer circuit using Jason P's 4agze tacho mod. Unfortunately still doesn't work.
Have a google search for: m48 tacho not working; 4agze tachometer modification; 1jz cressida tachometer modification.
This should give you a few starting points.

I would advise checking if the ecu has a tachometer output already set up in the MoTeC EMP software and go from there. If it's an M4 after serial number 3000 you can use a generic rs232 cable for laptop connection.

[Slimer86]

In the second photo there looks to be a Bosch ignitor attached to the coil packs. Check the part number reference on MoTeC drawings and see if the igniter has a tachometer output.
Also, if you still can't get it to work, give MoTeC a call.

From MoTeC Forum"Re: M84 Aux Output in Tacho Mode

Postby MarkMc on Wed Aug 10, 2011 5:03 pm
The outputs on our ECUs by default are switches to ground and do not "send out" a 12v signal. If the tacho does not work with the signal wire attached directly to an output you can try a 1000 ohm resistor bridging the signal wire to 12v."



Above link gives details with regards to using the resistor method and "gutted" relay method.

Good luck, and PM me with you're progress.

[buckas]

Thanks for the help. I'll try and get my head around it and see if I can get a solution. But it was what I was after, if I buy a replacement dash it may still not work. May just go the aftermarket tacho for now considering the dash already has holes in it to mount it and may look into replacing the dash down the track. Can't really afford the risk of getting a new dash and then that not working either atm

[Slimer86]

Got mine working today after 18 months.
Use circuit and motor from an ae82 twincam tachometer mounted into the ae86/85 dash.
Then use coil circuit linked from MoTeC.
Works a treat!
Also,if its m48,set it to alternate injector functions and use injector 5 for tacho. This frees up aux outputs.
Best of luck