Point numba Whan: NOTICE that the second drawing posted, the ECU connector is OPPOSITE the top drawing, IE you are looking INTO the front of the connector. This might save confusion.
Now, look at the top drawing, and concentrate on the RIGHT side of the dual ballast. This RIGHT side of the ballast is wired EXACTLY the same as your original!!!! Notice at the far top right says "existing wire" going off to the top right --- This is the same point as the connector on your existing ballast which comes from the KEY
The lower right connection on the 4 pin ballast is the same as the remaining factory connection you have on your original ballast. This diagram does NOT show the brown bypass circuit which is the second (brown) wire going to your original ballast.
SO---!!! If you have a newer 4 pin ECU (2 pin resistor) YOU HAVE ONLY ADDED one power wire!!! -- that is the additional wire, spliced into the "key" side of the ballast wiring, which goes to the box!!!
Now to check the "box" for 4/ 5 pin is a little more complicated, look at the top diagram. Find the wire coming off the LOWER LEFT of the dual ballast and follow it down to the connector on the ECU. THIS is the "5th" pin which will have no connection in a 4 pin box. (Some boxes this pin is missing)
Take a clip lead and carefully connect to this pin and leave it there, and put your meter on "high" ohms. Be CAREFUL that you do not get your fingers on the probes, as your body will show a reading. Now measure from this pin to all the other pins, as well as the box case. If all these readings show "infinity" then turn the probes of your meter around to reverse meter polarity. This causes a DC polarity change. Now re--do the test to all the other pins and the case. If both these tests show infinity on all counts, then you have a 4 pin box.
To repeat what may be obvious----
An older, 5 pin ECU MUST have a 4 pin resistor
A newer, 4 pin ECU CAN use EITHER a 2 or 4 pin resistor, simply that the second resistor does nothing.
Any replacement new box you buy nowadays will be a 4 pin box.
Make absolutely certain that your ECU is WELL GROUNDED. Clean the box mount holes, the firewall, and use star lock washers
IF you end up having a 5 pin box / 4 pin resistor, NOTICE the "upside down U" at the bottom of the drawing. This is important, as this orients the resistor block, as the two sides are DIFFERENT resistance.
If you are using a 4 pin box, you can leave the original coil + wiring, as well as the original ballast. All you need is to splice into the "key side" and add a power wire to the box.
In fact, if the box was to go bad, and you wanted to toss your old points dist. in for an emergency, all you need do is pull the coil neg. wire off, and plug in the points distributor!!!
rayer: :banghead:
