Shift light blinking under a load

[OrangeMustangGt]

My old shift light would do this....it blinks to the engine speed, but only in higher load times...

I just got a new one, and it does the same thing!

any ideas? its the proform style that has the knob on the back with the grounded trigger wire to the - coil wire.

 

[OrangeMustangGt]

....noone has a idea right? yeah me too.....im no idiot with electronics, but this has me baffeled

 

[95Vert]

May be a stupid question, but how good is the connection. I had something similar and my coil contact was loose.

 

[SQUEEZE&STROKE]

I had the proform shift light and it never did this...

I had mine hooked up to the MSD box though.

 

[HISSIN50]

S&S brings up something I wondered about Kyle (if you still have an ignition box). The multiple sparks can confuse shift lights.

 

[95Vert]

FWIW, I was told it was best to you just hook up to the coil, so I did.

 

[SQUEEZE&STROKE]

S&S brings up something I wondered about Kyle (if you still have an ignition box). The multiple sparks can confuse shift lights.

Thats the funny part though...I had it hooked up to the tach output on the MSD and I have had 0 issues with the proform and now the Autometer one I have.

 

[OrangeMustangGt]

I double checked my connections...they all seem good. I have the green "trigger" wire from the shiftlight ran back to right where the (-) terminal is on the coil....all new wiring from when I had my proform, also my mallory box died on me so im running stock ignition......Also new coil since then, im running a mallory, and new coil connector.

What gets me is that it only does this quick flashing when the car is under a bit of load.....cruising it stays off, but if im in 3rd,4th,5th and accelerate 10 or so mph and the car lugs a bit it goes off.... and its only 1/2 brightness...it flashes to the rpm of the engine!

So yeah, crazy! The only other thing I can think of is possible a arcing plug wire on the engine....but why only under load?!