gigabot

I recently purchased a 90 N/A and I'm trying to get it back into running shape. The electronic OMP had apparently gone out in it, so I bought a used OMP to replace it. My question is this: when I do the FSM resistance check on the "new" OMP's stepping motor harness, the wiring seems to be backwards from that of my old OMP. I'll attempt to explain what I mean. The harness is labelled like this in the FSM:

+--------=-------+
| SM3 +B SM1 |
| SM4 +B SM2 |
+-----------------+

You're supposed to get 19-23 ohms between pins +B1 and SM3/SM1, and 19-23 ohms between +B2 and SM4/SM2 on a good unit. The obvious problem is the diagram doesn't show which B is B1 and which is B2. On my old OMP, there was resistance between SM3/SM1 and the top B pin and SM4/SM2 and the bottom B pin. On the new unit it's flipped: the resistance is between SM3/SM1 and the bottom B pin and SM4/SM2 and the top B pin -- so it's exactly opposite from the old unit.

Does anyone know which way is correct, or will it function correctly either way? I'm already having to replace the ECU because it fried at the same time as the original OMP, the last thing I want is to fry the new one because the harness is wired wrong.

Gene

iTrader: (1)

Are you looking at it the right way? I think all the diagrams in the FSM are done from the device side not the pin side of the plug.

gigabot

I'm testing the OMP side of the harness, so I'm doing that part right at least, since the test is measuring the internal resistance of the stepping motor. The resistance is supposed to measure between 19-23 ohms and sure enough my old OMP had one pin where the resistance was down to 2 ohms, although the other three were still within spec. I'm just not sure if maybe the center B+ pins on the new OMP are swapped or if that's the way it's actually supposed to be.