1977 (late) Temp sensor sub-harness question (1 Viewer)

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Coolerman

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I am refurbishing a 12/1977 FJ40 main cowl harness. I am in need of the following information...

The water temp sensor connector on the harness side is a two terminal connector. I have never seen a two terminal sensor. However, while digging through a parts box, I came across this sub-harness:

IMG_3285.JPG


Overall length is about 8 inches. It is a single white wire going to a 1 pin connector. Is this in fact the temp sensor sub-harness?
 
That looks a lot like the jumper from the starter to the igniter to give direct 12VDC for cold starts
78 FJ40's had them.
 
I have two temp senders on my 77. Perhaps the two terminal connector uses one wire for each?
 
Alright. It’s a rare day where we see a question from Coolerman. Coolerman is constantly helping people, let’s call in the cavalry.
:beer:

:D Oh no, I have MANY questions! I just research before asking and usually find the answer. Harness details are one thing that are very difficult to find in a search. The engine side sub-harnesses on later trucks are often missing and there is little data about them.
 
my 12/76 is single wire going to temp sensor. A quick look around and I dont see anything with that connector and two wires.

Yes the 1976 only had the one wire connection. The later 77's and 78's had the two terminal connector but only one wire was actually used and went from the temp sensor to the gauge cluster for the water temp meter. The other wire in the harness is a red wire, and is actually connected to ground. One of the few places Toyota used a color beside White/Black for ground. Maybe Toyota was planning to use a sensor that did not depend on grounding through the engine block, but changed their mind for some reason?

Your pic actually answered my question though. The 78 is the same, it just has the two terminal connector. I will build a new one for my customer using salvaged parts as new two pin connectors like that are NLA.

Thanks all!
 
The red wire was used for a temp switch in the emissions circuit.

Yes the 1976 only had the one wire connection. The later 77's and 78's had the two terminal connector but only one wire was actually used and went from the temp sensor to the gauge cluster for the water temp meter. The other wire in the harness is a red wire, and is actually connected to ground. One of the few places Toyota used a color beside White/Black for ground. Maybe Toyota was planning to use a sensor that did not depend on grounding through the engine block, but changed their mind for some reason?

Your pic actually answered my question though. The 78 is the same, it just has the two terminal connector. I will build a new one for my customer using salvaged parts as new two pin connectors like that are NLA.

Thanks all!
 
Can you explain that a bit more? The red wire is grounded to the harness ground circuit and goes nowhere so how was it used? I do not have any Emissions schematics. If you do, could you post them so I can see exactly how that worked?
 
Power Valve circuit for CA emissions.

Bottom of zone 8 on W/D.
1978 Wiring Diagram5.jpg


Upper left corner.
smog5.jpg
 
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No problem.
 

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