M.Bonanni Posted December 24, 2015 Share Posted December 24, 2015 Car is a '78 280Z with air conditioning and manual trans, only reason I state that is because it may or may not pertain to this particular knob... After doing as much research as I can I am fairly certain this is not factory or has at least been tampered with if it is factory, I can't for the life of me figure out what it could possibly be for though as from tracing the wires it seems air conditioning related. It's a factory air conditioned car, but it doesn't currently work so I can't tell if turning the knob has any effects on the AC. It doesn't appear to have any noticeable effects on anything else. Some of the wiring connections are definitely not factory, some look like they could be. Here's where the wires go, hopefully someone on here can help diagnose so I can see if I need to keep it or if I can remove it. Black Wire: Goes from the knob straight to the AC compressor in the engine bay. Bare Wire: Goes from the knob into the AC vent/fan motor unit behind the dash. Without completely tearing this apart I can't see where this wire ends exactly. Green Wire: Goes from the knob around to the passenger footwell and is spliced into the C7 connector's solid green wire. From there that green wire goes through the following journey, making multiple splits... - Fuse box - Brake Warning Lamp Check Relay - Seat Belt Warning Timer Unit - C6 connector > Fuel Level Warning Lamp - C4 connector > Back Up Lamp Switch White Wire: Spliced off of the green wire, end is cut, no connection to anything. The green/black/bare wires are the only ones attached to the unit. My guess is that the green and black are in/out power sources and the bare wire is ground or some sort of temp sensor, and the white one used to power something that's no longer there. My best guess is that it is some sort of factory temperature control adjustment for the AC system. Why it would be there instead of using the factory one though I haven't the slightest idea. Any theories? Quote Link to comment Share on other sites More sharing options...
seattlejester Posted December 24, 2015 Share Posted December 24, 2015 Looks like a rheostat of some sort, it regulates voltage or current (sorry kind of out of it at the moment). The green wire I believe is the universal power supply to the gauges so the signal wire. My guess would be that this reduces voltage to the fan or increases voltage. Really can't tell much more then that. Your guess of a temperature control would not be far off I imagine. Quote Link to comment Share on other sites More sharing options...
djwarner Posted December 24, 2015 Share Posted December 24, 2015 Definitely a thermostat. Quote Link to comment Share on other sites More sharing options...
crankman52 Posted December 24, 2015 Share Posted December 24, 2015 It is a rheostat control for the A/C. Same as on my 240Z. You turn it to control the level of the A/C. Quote Link to comment Share on other sites More sharing options...
PLATA Posted December 24, 2015 Share Posted December 24, 2015 An A/C knob as mention . FWIW. Quote Link to comment Share on other sites More sharing options...
M.Bonanni Posted December 24, 2015 Author Share Posted December 24, 2015 Thanks everyone! Next question is, where is the factory location? Or was this some sort of work around done by a previous owner? I can't find any photos with it in a 280Z. Previous owner had it mounted on the side of the center console. Quote Link to comment Share on other sites More sharing options...
cgsheen Posted December 25, 2015 Share Posted December 25, 2015 There is no "stock location" for that part. My guess is that the stock "microswitch" that's connected to the temperature slider stopped working properly and they installed that as a work-around... My microswitch is sticky and doesn't work quite like it should, so I can see someone doing that. I'm just going to try to fix my microswitch or swap it out. Just look in the A/C section of any FSM for the 260Z or 280Z and you'll see what I mean. Quote Link to comment Share on other sites More sharing options...
M.Bonanni Posted December 26, 2015 Author Share Posted December 26, 2015 There is no "stock location" for that part. My guess is that the stock "microswitch" that's connected to the temperature slider stopped working properly and they installed that as a work-around... My microswitch is sticky and doesn't work quite like it should, so I can see someone doing that. I'm just going to try to fix my microswitch or swap it out. Just look in the A/C section of any FSM for the 260Z or 280Z and you'll see what I mean. Copy that, thanks! Quote Link to comment Share on other sites More sharing options...
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