Okay; original twenty-some-odd year old box and instruction sheet is in front of my eyes.
DISCLAIMER:
If someone's truck burns to the ground or melts into oblivion, I take no responsibility for the following; proceed with educated caution and a clear view.
Looking at the terminal end of the flasher, three terminals, one at 9-O'Clock, one at 3-O'Clock, and the center at 12-O'Clock.
9-O'Clock is fused HOT.
3-O'Clock is LOAD, which should be YELLOW.
12-O'Clock is PILOT, which should be BLUE.
The GREEN wire should connect to the FRONT LEFT signal wire.
The RED wire should connect to the FRONT RIGHT signal wire.
The factory switch should be dis-connected/un-plugged at the column and this should render the factory flashers dormant.
Is that MACK where you can look under the dash and behind the driver seat ??
Just about all wiring should connect at a couple very long terminal strips, with any relays and associated goodies in the near vicinity.
Taking a good look at that should help understand just what goes where.
On the box, I have a crude drawing of what I think may be the factory plug at the column; it has been many years and I am not certain.
Large YELLOW wire with BLUE DOTS = HOT.
BEIGE wire with RED SPIRAL DOTS = ??? maybe KEY=ON=HOT but not certain.
GREEN wire with a RED STRIPE = LEFT BRAKE LIGHT.
ORANGE wire with a BLUE STRIPE = RIGHT BRAKE LIGHT.
LIGHT BLUE wire = TURN SIGNAL FLASHER.
GREEN wire = BRAKE PEDAL SWITCH.
BLACK wire = ??? maybe HAZARD FLASHER but not certain.
GREEN wire with a WHITE STRIPE = LEFT FRONT SIGNAL.
WHITE wire with a BLUE STRIPE = RIGHT FRONT SIGNAL.
DARK BLUE = HORN.
UNKNOWN COLOR wire = badly faded and can't make out what it says.
If this 4-wire controller will not work on our model of trucks, then your money will be better spent buying a proper 7-wire controller, than buying an electronic gizmo to make it work.
Look around big truck junk-yards and swap-meets and you should find plenty of 7-wire controllers for cheap.
I see lots of them at swap-meets.
ALSO, I just remembered, these controllers assume a GROUND via being firmly strapped to the column; the problem is that the outer coverings of our columns are isolated from GROUND.
To get the little indicator lights that are made in the controller to work, I had to add a GROUND wire to the clamp-strap.
If you opt for the 7-wire, I have the diagram for that also.