Tapping tach signal from Diagnosis box cuts signal to stock gauge :(

[03MSP]

Well, operation megasquirt is finally going, I'll update my original thread when it gets done, but I have a minor problem at the moment.

When I tap into the violet/white wire for tach signal, either at ECU, or at the diagnosis box under the hood, my stock RPM gauge sits at zero. However, car runs fine, and megasquirt gets the tach reading.

I am wondering first off, why is this happening, and secondly is there any way to get both of them to work at the same time?

Thanks in advance....

 

[jurgs01]

Well, operation megasquirt is finally going, I'll update my original thread when it gets done, but I have a minor problem at the moment.

When I tap into the violet/white wire for tach signal, either at ECU, or at the diagnosis box under the hood, my stock RPM gauge sits at zero. However, car runs fine, and megasquirt gets the tach reading.

I am wondering first off, why is this happening, and secondly is there any way to get both of them to work at the same time?

Thanks in advance....

How did you tap the wire?

 

[03MSP]

I did not cut the stock wire, I shaved the wire coating off and wrapped the wire to megasquirt around that.

 

[low_psi]

Search for some old Microtech threads, from when Terry @ Spool was using it up until Steve @ NSN getting the tach to work. They had the same issues with both the alternator and tach signals IIRC. Can't recall what the exact reason was though.

 

[03MSP]

OK, thanks, I'll check that out.

 

[HiBoost TS]

OK, thanks, I'll check that out.

Pm me and I will let you know what you need to get it working properly

Juan

 

[03MSP]

Heh, I actually did after i made this thread =P

 

[daedalus]

good luck with it brando...

hopefully i'm getting the microtech on my car next week... but i blew my brake lines last night so its at the stealership as we speak. I expect to actually get to see your car one of these days.

 

[03MSP]

good luck with it brando...

hopefully i'm getting the microtech on my car next week... but i blew my brake lines last night so its at the stealership as we speak. I expect to actually get to see your car one of these days.

Yeah, I really want to get it tuned and have some fun. On the plus side, I can see Coolant temp, air temp, Throttle Position, and 02 voltage on my Megasquirt!!!!....yeah I know that means nothing, but baby steps...baby steps.

 

[wicked]

you can hit up hdh 51 on AIM,he is a megasquirt guru.

from what I understand he mainly does volvo,but none the less he still knows the s*** out of mega(bj) .

 

[t3ase]

I'm very curious as to why it would interfere with a signal wire. We type in to vehicle speed sense and RPM wires all of the time for alarms and cruise control installs and never have we had this issue.

That is unless the Megasquirt is feeding back in to the signal line.. If that's the case, diode isolate it.

 

[girth]

I was thinking the exact same thing. Rather than keep it "private" with HiBoost can you just let everything here know what you did and why you had to do it?

 

[Captain KRM P5]

subscribing for future updates

 

[03MSP]

Diode isolate it? Yeah, probably should know what that means considering I'm taking on a project like this, but please, enlighten me

 

[Dexter]

put a diode inline with the megasquit wire, so that the current only flows to the MS wire and not back into the stock signal wire.

 

[t3ase]

true, true.

 

[03MSP]

Gotcha, thanks, I'll try that.

 

[jurgs01]

put a diode inline with the megasquit wire, so that the current only flows to the MS wire and not back into the stock signal wire.

Uh, a diode will block all forward-biased current if it is biased at equal to or less than 0.65~0.70V. It will also reduce the voltage by that much from the source to sink side. I wouldn't just throw a diode in there without knowing the operating voltage and tolerances for the signal.

 

[Dexter]

oh, right, forgot about that. well then.

 

[yellerandahalf]

dude, I tapped into the rpm wire for megasquirt, and my gauge works fine. what in the hell? Make sure you're not plugged into the tach out pin on megasquirt, but the RPM pin instead. Also, where did you tap into the wire exactly? I used a 3M tap-splice connector, and worked great. this is frickin wierd. What timing system are you planning on using for the Protege? I'm wiring up my EDIS setup this weekend Very good luck to you sir, and PM me if i don't respond, i may forget to check the thread.
-mateo