Tach signal

[18yr240t]

I'm using a 139 module wired:
#1 -on coil
#2 ground
#4 switched 12v
#6 to ms
The problem is both terminals on the coil are hot all the time and no tach signal, any ideas?

[Sp3aK]

I don't readily know the answer to your question, but when I installed a tach on my car I ran a wire to the coil for tach signal... maybe your coil is differen't from mine?

[towerymt]

What else is plugged to the coil?

My 139 is wired the same on my '87 240.

- I ran a new wire from the fuse panel (powered while running AND cranking) to power the coil (#15 is power, #1 is ground)

- On the 139, #1 blue runs to #1 on the coil (neg.)
- On the 139, #2 is grounded
- On the 139, #4 green/white runs to #15 on the coil (switched 12v)
- On the 139, #6 brown runs to pin30 on MS (yellow on my Kenny-harness-stub)

Faulty module? Time to get out the test light and see what goes wrong when. Disconnect wires til you narrow it down.

[18yr240t]

switched 12v t cranking to 15 on coil
pwr to distro from 15 on coil with 10 ohm res
signal from distro to pin 25 on ms
blk to grnd
pin 24 on ms to 12v with 380 ohm res
pin 6 on mod to pin 30 om ms
It makes the coil spk once when I turn on the key then nothing.

[PetesDustyVolvo]

switched 12v t cranking to 15 on coil
pwr to distro from 15 on coil with 10 ohm res
signal from distro to pin 25 on ms
blk to grnd
pin 24 on ms to 12v with 380 ohm res
pin 6 on mod to pin 30 om ms
It makes the coil spk once when I turn on the key then nothing.

I'm not running a 139 module but I think I have a pull-up resistor somewhere on the harness i made for my 124 module.

any pull-up resistors? can anyone else speak to this?

[18yr240t]

There is a 10 ohm on the pwr to the distro t on distro. There is a 380 ohm on the wire to pin 24 on the ms from switched 12v, exactly as kennys updated wire dig. I just double checked all the wires and 12v while cranking.

[PetesDustyVolvo]

There is a 10 ohm on the pwr to the distro t on distro. There is a 380 ohm on the wire to pin 24 on the ms from switched 12v, exactly as kennys updated wire dig. I just double checked all the wires and 12v while cranking.

yeah but I think you might need another pickup resistor chilling over by the ignition module. I will try to double check on this when i get home. I know i have something funky going on in that section of the wiring and it wouldnt work without it.

[towerymt]

I've got a 370 ohm between pin 24 and 12v. And I"ve got the 10ohm on the 12v dist. hall sensor wire. But that's it for mine.

Start ruling things out. Got another 139? Verify wiring with a test light & multimeter.

[18yr240t]

I have a 124 but not another 139. I have verified power and ground with a test light and a multi meter, is there a way to ck the module?