[ngoma]

I forget the model year range for the biodegradable Bosch wiring used in these cars, but 1985 is solidly in that range. My experience has been that the wire insulation deteriorates mostly in areas that see heat, oil, and flexing, esp. where it runs along the engine block (both temp sensors, oil pressure sensor, the bundle that runs tight beneath the oilpan and around the oil filter, etc.).

Probably no good used replacements because of the limited MY range and low production numbers of these cars with the diesel option, and most of those are the Bosch junk wire that has similarly suffered.

Best low-mediuim budget solution is to closely inspect the wiring in these areas and replace with good quality wire/connectors as required, or at the minimum paint the exposed conductors with liquid insulation brush-on type product. Might need to slice open the hard black plastic sleeving to verify the wire condition. Happily, the diesel models have far less complex wiring harness than the gassers.

Most of the other chassis and interior wiring I have seen seems to be less problematical, because of milder environmental conditions. Less intense heat, vibration, chemical attack. Electric window switches are almost always inop/dirty, and relay connectors (behind the ashtray) are also well-known suspects, much more than the interior wiring.