Terminals 10 and 12 on the computer connector are connected to the two ends of the EHA connector (do you have the diagram for that connector ?), check for continuity for each wire before buying a new harness. If these two wires show continuity, for sure the computer is not sending the current correctly. The model you described, should either have 10 or 20 ma (depending on the year) as soon as the ignition switch is put on run (position right before the start). I dont know of anything else that can cause the EHA current to be absent, maybe someone else with more experience can pitch in OTHERWISE just replace the computer. Oh, one more thing, try disconnecting the battery for 10 or so minutes, just incase the computer needs a reset.

It is unlikely, but possible that both pots are bad, you should not have a sudden jump (i.e. like an open circuit) at all for any plate position, I can check this on my car and let you know. I dont know if the pot is linear or logarithmic, would expect it to be linear. But in either case, I am not sure if this will cause the EHA current to be absent.

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Saumil S. Patel