MS installed, No more dashboard tach
 

Alright so this is my first experience with Megasquirt here. If anyone has any ideas or possible solutions to my problem I would greatly appreciate the advice.

I recently purchased a standalone MS setup from Braineack. After I completed the install, I started up the car and the tach on the dashboard does not work.
Megasquirt sees a tach signal, as the car runs.

The car: 1995.5 Miata - 3 wires go into ignitor
The Megasquirt: 95 standalone Brain built DIY MS 1 v 3.0

What I have tried so far:
Setting Tach Output to "JS0" and Pin10
Jumper from B+ and IG- in diagnostic box, with 1k 1/4 watt resistor

1: Jumpering B+ to IG- with no resistor in between is bad. High probability of frying something with that move. What this is doing is putting 12 volts with no current limit at all onto a circuit that's giving closures to ground.

2: When you say "4 wires go into ignitor" does this mean that each of the two ignition coils has four wires going into it?

Joe: I did jump the 2 points with a resistor I left that part out on my post.

There is a plug that goes into the ignitor and it has 4 wires on the plug.

Is it possible that the tach output is just going to the wrong wire?

I did not build the tach output circuit for him and I've never had the for the circuit with a 94-95 standalone MS before. So please, no more responses about a wire in the wrong spot or the circuit built incorrectly...

I have a feeling he has a 95.5 that does need the circuit as the coils don't send the tach signal back to the dash.

You did build mine for my 94 standalone, and I did have to move a wire. I also had to solder the MAP sensor to the main circuit board when I discovered that it had been overlooked.

Unless you were the only other person with the no tach issue on a 94-95 that I've built, no one else has told me about the issue :vash:

I didn't know there such hint as a 95.5 so I'm subcribing

I have a 94, and my tach does not work in my dash either. But, I have been too lazy/busy to try to sort it out. LINK

well crap...looks like I need to build the tach output circuit for you guys then...probably like 20 of you driving around without tachs... sigh

Big dumb mistake on my part! The connectors I looked at weren't actually going into the coils. The plugs going into the coils have 3 wires. :facepalm:

I just installed the basic pullup mods, Joe's spark mod, and installed a 1K resistor between +12v and 2I for my 94 standalone. Dash tach works great...

Attachment 199414

If you have a 1.6, or an early 1.8 (up to mid-95) where each coil has four wires, then all you need is a resistor to pull up the tach line, and the coils will drive it.

Late '95 and onwards needs a dedicated circuit inside the MS to drive the tach. The coils aren't part of the equation.

It's not complicated to do:

http://msextra.com/doc/ms1extra/MS_E.../LowVTacho.GIF

The line that says "to tacho" goes to the wire on your ECU connector that drives the tach. On a '95.5, this is B/W at 2I.

The line that says "MS PCB" goes to whatever pin has been selected in software to drive the tach:

http://img38.imagefra.me/img/img38/2...xm_5dac91e.gif


Moar: MSnS-Extra Hardware Manual

That's what I thought, thanks for confirming. Seems he has a 95.5 that needs the circuit and I'll gladly build it for him and anyone who needs it that I build a 95 MS for.

Buffon needs to jump his diagnostics box as he's confirmed 4 fours wires in his coil connectors.

I don't remember my fix exactly, I thought it was just a wire change, but I found a pack of resistors with my soldering iron this afternoon, so I may have inserted a resistor too. It wasn't a big deal (nor was the map sensor), that's why I never brought it up.

Then you need to run to radioshack and buy a pack of 1/4 watt 1Kohm resistors for .99c. Then jump IG- and B+ with one in your diagnostics box. This pull-up so power the tach signal yet again and your dash will come to life.

The map sensor thing is all on me. It's usually the last thing I put on the board and that must have slipped my mind after fitting.

I think from this point on I'll just build the tach circuit for every 94-97 MS I build, it's easier for me to just add the extra circuit and wire in the harness from the get-go without the need for you guys to have to do anything extra on your end when installing or falling to check if you're a 95.5 and ending up in a situation like hellothere.

Like I said, it was no biggie. You saved me a lot of time and trouble doing the assembly, I still got to do a little hands-on for the build, and all is kosher.

:hsugh:...Why I was not previously able to figure out that 'tacho output pin' has something to do with the tach is beyond me.

Mine is set to OFF.

Scott, which selection should I try? I do not have my laptop with my, but I think 'X2' is the fans (which is another story), and I think the rest may be unused.

no selection, you need to go grab a 1K 1/4 watt resistor and jump IG- and B+ plus in the diagnostic box with it. That should solve it. I used to build the pull up resistor into the harnesses, then found it was easier having people jump the signal and provided a resistor to use...and then it simply slipped my mind.

To Braineack you listen.

Tach Output from the MS is only needed for folks with '95.5 and later three-wire coils. Anybody with a 1.6, or with a 1.8 with four-wire coils, can just pullup the stock tach wire which goes to the ignition system and let the coils do the work.

Good stuff. I will try to make a run to radio shack sometime soon.

I tried it on the cheap, and stuck the ends of the resistor in the diagnostic box. The tach needle did move about a millimeter when the key went to 'ON' position, then nothing when running.

I am about 95% sure that the ends of the resistor were touching the contact points in the d-box. Should I go ahead and try to do it properly, or does this suggest something else?

so this may be a really dumb question... but i plan on finally getting around to installing the MS braineack built for me a while ago .. and i don't know how to tell if i have a 1995 or 1995.5..... where or how do i check for 3 or 4 wires in the coil connectors .. rather .. where are the coil connectors?

The coilpack is what your plug wires fit onto. there should be two connectors coming off the back of it and plugged in somewhere behind the fuel rail. See if there are 3 or 4 wire going into each connector.

To prevent this in the future I'm simply building the tach circuit on each MS I build, since the circuit itself requires the pull-up, there will be no need for adding the resistor and if you have a 95.5-97, you can turn on the tach output in software.

I finally got this thing working. The wire for the dash tach on my car is at 1f! Apparently in 95.5 Mazda decided to fuck with everyone!

This kid Slacker also has a 1995.5 and couldn't figure out why his tach wasn't working. I thought I remembered something about this topic and did a search. Why isn't this a sticky in MS?

I have a 94 DIYPNP. My tach drops out at WOT. I will try the resistor in the diagnostic box. Anyone have a picture of how they installed the resistor in a clean manner?

Does a MSII on a 97 need this tach output circuit in a standalone configuration? I understand 4l is the Tach lead on the stock harness.

Yes, any MS on a '97 will require a tach output driver. And yes, on a '97, the tach output is a black/white wire on pin 4L.

Thanks..

In this configuration does it need a resistor on the diagnostics box?

It says try resistors between 1k and 10k. What do you use?

As far as I know if you have the tach circuit you DONT need the resistor in the DB.

which is because part of the circuit built within the MS is a 1K pullup to 12v...

which is exactly the same as the 1K reistors on IG-(tach signal) to B+(12v)

Lol, when I switched to COPs I got the resistor but never put it in. Since then I've had three co-drivers autocrossing with me. The little funnies always ask how they will know when to shift. As if they can't hear the limiter.

Well yeah, all I was trying to say is that depending on the car is either one or the other. W.e ya kno wa Im sayin