Hey folks! I just picked up an '87 4runner 22re with no AC and a set of broken aftermarket gauges. Well, the oil pressure works. No wires connected to temp, however.

Doing some research I saw that I have 3 coolant temp sensors, one up front (ECU), one up top (AC?) and one down between efi and valve cover (dash gauge). My truck runs fine and the stock gauge works, but it's not awesome and - hey - I've already got a better water temp gauge mounted so why not use it?

The top most sensor is plugged into a green wire with white stripes (i think it's striped, badly aged) which goes into a main wiring harness. From there, I have no idea. I pulled the cover from the dash where the gauges are installed (that lower center portion below the stereo right in front of the sticks is where they mounted them) and could not find any unplugged/loose wires. The 3 gauges are wired for the little crappy lights, the oil pressure gauge is hooked up correctly, but I don't see anything connected to or missing directly from the coolant temp gauge.

My question for any pros is about that green with possible white stripe wires. Is that a typical wire used for the AC sensor and if so where does that terminate/where can I find it? Is it typical for a non-AC car to have a temp sensor there and not just a plate? I am not sure if this is a stock setup that they tapped into or they added a coolant sensor and spliced into a random wire. I'd love to find where that goes without splitting the loom or just abandoning it for a new wire run. If it's already heading into my dash somewhere I'd rather just pick it up there!

Any advice is appreciated. This thing has been hacked and backyard mechanic'd QUITE a bit in it's 35 years of life - I trust nothing.

EDIT: Some reading leads me to believe that this '3rd' sensor is actually for a Fuel Pressure Up switch, (https://www.yotatech.com/forums/f116...ousing-275450/) which increases fuel pressure when hot to help with hot starts. Maybe the aftermarket temp gauge i have was simply never hooked up, just installed because boy does it look cool, etc. I'm guessing if that is the case, I'd need to find a proper sending unit and replace the factory one entirely and either run a new wire for it or take apart my dash to disconnect the wire from the factory gauge for reuse.

 

Here are the locations of the temp senders:

TEMP GAGE SENDER

AS SEEN WHEN TAKEN APART - It takes ground from the block so make sure there is no teflon or any insulating material on mounting threads.



OTHER TEMP SENDERS