What is this? Thermo Switch? 1973 240z

[Captain_Zeros]

Okay, so, I'm monkeying around with stuff and this is bothering me. What is the sensor with the two green wires going into the bit of metal between the radiator hose and the thermostat housing? I assume the one lower down with the single yellow wire is the temperature gauge sender. There are also another green wire and a black/yellow wire in the harness that have been chopped off since before I got the car that I'm a bit curious about. Disregard the 280zx distributor blocking the view of everything, that's my own hack-job wiring that I understand pretty well

[Captain Obvious]

That looks like the "Water Temperature Switch", but here's the problem... 73's aren't supposed to have one.

According to the FSM's that wasn't supposed to have started until 74. (Not that they aren't without mistake though, so who knows)

Here's a bunch of info about the water temp switch. Read through this and see if it makes sense.

http://www.classiczcars.com/forums/electrical-s30/46647-water-temp-switch-what-does.html

[Captain_Zeros]

Thanks for the link, I found that thread earlier today and couldn't find it for the life of me when I wanted to refer back to it!

The closest I could find was references to a thermoswitch in the cabin (which isn't so equipped on my car) for pulling timing on automatic transmission cars and/or controlling the EGR system my car may or may not have ever had in the first place and references to thermoswitches in other years. I'm real tempted to splice an idiot light into that thermoswitch thread it into the cabin so I can see what kind of range it has under real world conditions.

My ulterior motive is I'm considering an electric fan swap and having a thermoswitch threaded into a coolant passage could be pretty damn useful for that. The way I figure it probably isn't anywhere close to the temperature I want, but if I can find out what the threads are on it I might be able to source a thermoswitch that is... or adapters... or drill and tap... but all those things require draining the coolant which while not difficult, I don't want to do if it's not necessary. But I digress and ramble.

[Captain Obvious]

I'm thinking that it was an un-documented mid-year change in 73 and your car is configured more like a 74. Especially since you don't have the thermostatic switch inside the cabin.

And if that's the case, you're right... The temp switching points are nowhere near where you need them. From the FSM, the water temp switch characteristics are as follows (EC-28):

• Off (open) below 88 F
  
• On (closed) above 106 F
  

And that's if the switch even still works at all. Mine didn't.

As for pulling it out, it's pretty high up. You don't have to drain a lot of coolant to get below the level of that switch. Maybe a gallon? Sorry, but I don't remember what the threads look like. I don't even remember if they are straight or tapered.