Hello,
Trying to run my fan off the Megasquirt. The pot comes on, but I do not get a trigger voltage, and suggestions? Here is how I have set up the spare port.
Thanks ~ JEB

 

When the port comes on, it sinks voltage (becomes a ground). Look carefully at the attached wiring diagram regarding the Fidle wiring. The Fidle solenoid can be (I use!) a typical Bosch style 30 or 40 amp that should handle your efan just fine. You don't have to provide +12 to the relay exactly as noted.

 

Robert, can you spell it out for me, I am just not getting it. Do I run the relay on the ground side of the circuit instead of the 12v side? Just lost here.
Thanks for looking in ~ JEB

 

The 85 or 86 terminal on the relay will have +12 on it from a switched source. 85 & 86 are not polarity sensitive so for sake of argument we'll say 85 will get the +12. Now, to activate the relay you ground term 86 on the relay. That will close the contacts between 30 & 87 allowing high amperage current to flow to power your efan. The ground to 86 is provided by the MS Fidle circuit - when the port is activated, a small amount of current can flow to ground triggering the relay to "on" and controlling the much larger fan current. Hope this helps!

PS: you'll want the +12 to be switched so it's not hot all the time - if the MS is off you don't want the relay coil to be powered.

-Mike

 

Perfect, I will give that a try Robert.

Hey, one more question for you. Is there a spot on the relay board that I can get a tach signal for my tach? I figured that the tach spot is an input, out an output.

What do you say?

Thanks again ~ JEB

 

Depends on the tach - many work off the signal at the "-" coil primary. What kind of tach do you have?

 

Robert, I am using an MSD 6AL powering the coil, so I cannot use the "-" of the coil, the added spark will kill my Autometer tach. The MSD 6AL has a tach outpout, but it does not work. I was just looking for another place to get a tach signal.

 

OK, I understand now. I think you're using MSExtra code so http://www.msextra.com/doc/ms2extra/...e.htm#tachoout is applicable to your need. There is provision in the code to do what you need but the external interface can vary as the link indicates. A large value resistor off the coil (-) may work but would require a little experimentation.

PS: how are you triggering the MSD unit? The MS spark outputs? That trigger signal may be enough to operate the tach without interference if the tach input is sufficiently high impedance. I have a spare Autometer tach at home and would be happy to see if the +5v MS spark signal would trigger it - but - I'm 800 miles from home right now... If you're still looking for a solution after 7/17 please feel free to remind me and I'll take a look at what that tach actually needs.