electrical short '97 NAS D-90 SW - Defender Source
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Old October 30th, 2011, 03:09 PM
blenkush's Avatar
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Severin Blenkush
97 D90 LE, 10 Lotus Exige S, 05 LR3
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Location: Yorktown, VA
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electrical short '97 NAS D-90 SW

A few weeks ago I asked for help on a short that was blowing the #17 15 amp fuse on my '97 SW. Checked all the suggestions with no luck. Pulled out the center console to find several melted wires coming from the relay closest to passenger side. A green wire and a slate (grey) with black stripe. The green wire only melted a few inches from the relay. The slate with black stripe melted a LONG way down the loom. I found a wiring diagram for a '97 but don't think is is for a NAS (no mention of A/C) as I can't find the slate/black wire anywhere. I think I've traced that wire to the front most plug on the ECU. I could get the truck started by inserting a fuse and quickly hitting the starter before #17 fuse blew. Once running it was fine minus everything on the #17 fuse circuit.

I had recently replaced the A/C receiver drier, two A/C lines, and the A/C compressor trying to get the A/C functional after a period of inactivity. The tech who flushed/applied vacuum/filled the A/C system said I also needed to replace the expansion valve, condensor, and evaporator because they were clogged. The compressor would turn off due to "excessive pressure". Not sure if this could be a symptom or cause but thought I'd mention.


What is the slate with black stripe wire for?

Any ideas what would/could cause the kind of short that would melt wires starting at the relay?

Suggestions for proceding?

Best way to repair the melted wires?


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Old October 30th, 2011, 05:29 PM
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Neill Thornton
1984 D90 300 Tdi / 1965 Series IIA
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According to the NAS 90 diagram, the slate/black wire comes out of the ECU as a command signal to turn on the condenser fan, labeled as relay 182, pin 4, by grounding it. The power for that relay is on pin 2 of the relay and via a bunch of splices, eventually getting power from fuse 7. Fuse 7 also is your main ECU power, so if it blows you are hosed.

As for the melting, I would say that the relay shorted somehow.... the ECU commanded the fan to turn on, but the relay was shorted inside, and it melted the wire. The fuse is big enough (20 amp) that it didn't blow in time. That's a SWAG.

Fuse 17 seems like a lot of unrelated stuff... rear window wash/wipe, brake lamps, hazards, but DOES have the compressor clutch relay, A/C blower relay, and even worse the engine immobilizer ECU!
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