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172 electrical issue

  Clio 172 sport
Hi all,

Got a really annoying issue with a 172 sport track car project, where it blows one of the 20a fuses on the interior fuse panel whenever you put it in reverse with the engine running. With the engine off, it won't blow the fuse, but the dash lights dim (and wires to the reverse switch get warm) so it definitely seems like a short somewhere. I am really confused why it blows the aircon (climate control) fuse. It can be prevented by keeping the air fuse out or disconnecting the reverse switch. I initially thought it was wiring (as reverse switch wire was melted by the old gearbox which had overheated as the previous owner had no oil in it), but I just spent some time to replace the entire engine wiring harness with one from a known good parts car, but the problem still occurs. checking with a multimeter both pins on the plug have a ground when unplugged on both harnesses.

Also to note is, ever since picking up the car, the climate control has not worked at all. The display worked (until recently, now only the backlight turns on ughhhh) and all settings could be adjusted but nothing would happen. So far the BCM (and ECU), climate control unit and engine wiring harness have been transferred from the parts car from which it all worked (from what I think, only the interior wiring has stayed, but none of it looks damaged). I also know that the blower motor works when power is put there. I have tried everything and cannot find why these two problems still exist and to what extent they are related. Really getting close to just wiring in my own switch to run fan and leave the reverse switch out. Any help is greatly appreciated with advice or wiring diagrams cause id kinda like some aircon on the track when it gets hot again. Thanks,