4 wires into computer controlled HEI
Thread Starter
Instructor
Joined: Jun 2003
Posts: 183
Likes: 0
From: Gordonville MO
4 wires into computer controlled HEI
Anybody know what the function for each is? (81 Vette)
Like power in, signal out, ground, etc etc.
Or, a schematic of the wiring in the whole HEI would be really
wondeful :-)
Thanks
Like power in, signal out, ground, etc etc.
Or, a schematic of the wiring in the whole HEI would be really
wondeful :-)
Thanks
Safety Car
Joined: May 2001
Posts: 3,758
Likes: 3
From: Surrey
Re: 4 wires into computer controlled HEI (macx)
Here ya go:
Pin A (white) - EST
Pin B (purple/white) -Ref pulse hi
Pin C (tan/black) - Bypass
Pin D (black/red) - ref pulse lo
Bypass is 5v if ECM controlling the spark advance, 0v if HEI module controlling it.
I think the ECM uses the ref pulse lo/hi to measure the rpms? The lo is effectively the ground. Chassis ground isn't used due to noise/interference that could be present.
EST is the pulse sent by the ECM to advance the timing.
:cheers:
Pin A (white) - EST
Pin B (purple/white) -Ref pulse hi
Pin C (tan/black) - Bypass
Pin D (black/red) - ref pulse lo
Bypass is 5v if ECM controlling the spark advance, 0v if HEI module controlling it.
I think the ECM uses the ref pulse lo/hi to measure the rpms? The lo is effectively the ground. Chassis ground isn't used due to noise/interference that could be present.
EST is the pulse sent by the ECM to advance the timing.
:cheers:
