86 Turbo Z Power Module issues

Hey Everyone,
I've been toying with my stock 86 Daytona and I can't seem to have any luck with the power module. As I recall, the power modules rarely went bad, and and the Logic Modules were often the root cause of computer problems.
Well, I have one Power Module that intermittently makes the engine idle very high-- 2,000-3,000 RPM. Another Power Module will allow the engine to idle normally, but the will not allow the alternator to charge (voltage regulator issue?) The third Power module will idle ok, no charging issues, but sometimes the fuel pump won't prime at start up, so the engine will turn over and not start. Do I just have a bad collection of Power modules?

On another note, does anyone know which relay is the horn relay in the bay of relays? I think mine is bad.

Thanks in advance for any help!
-Lee

The horn relay is in the fuse block under the dash if I'm not mistaken.

I'd be very leery of an electrical problem with all of those different issues when switching between PMs. However, there could be a bad ASD relay in one, a bad voltage regulator in the other, and I would suspect the 3rd one must be putting out a funky signal to the sensors, throwing off the LM's ability to read them correctly. I think that last one is much less likely than the other two problems.

The wiring harness is in pretty bad shape. For example, the two plugs that go into the PM, almost all the wires are cracked and exposed copper, however none of them touch. It seems to me the Power Modules each have their own consistent problems, so I'm not positive wiring is the issue, although I do have plans to replace the wiring harness with another one that is in better shape.

I had a very poor condition wiring harness in my old Omni which would cause boost cutout at 6PSI. Consistently, and every time, the car would cut out. I thought for sure it was mechanical, then I thought for sure it was LM/PM/cal related. After a couple of years, I put a new harness in it, and when revived, the car ran with no issues. It was night and day, as the car went from cutting out at 6PSI, to the new owner suggesting that the car needed a 6th gear. Grrrrr...

hmm....this motivates me to get that used harness in shape..... I plan to replace all the plastic wire loom on the replacement one. Only possible issue I noticed on the replacement one I have is the white plastic block which connects to the starter is all melted away, but the connections still look fine. Any ideas on what to do about that?
Thanks for all the help!!
-Lee

I've had some pretty rough looking pieces in that area. I generally just use care when installing the two connections so that they don't contact each other or the block. I've had no issues there.