F20 temp gauge problem

[Ammann]

Hi all,

I'm trying to sort out a little bug with my temp gauge on my 1977 F20. It has the Toyota 5R engine which looks very similar to the 12R. Currently the wires are disconnected from the senders.

I see two temp senders, one before and one after the thermostat. I see two wires that look like they want to be connected to the senders, one red and one yellow/green.

Now when I connect the yellow/green to either sender the gauge shoots up to max as soon as key is turned to ON. Connecting the red wire to either sender does nothing - the gauge stays at zero.

Something is up. I'm suspecting the gauge and possibly the wiring.

What are the red and yellow/green wires supposed to connect to?
Conversely, What colour wires are supposed connected to the two senders?

Does anyone have a good wiring diagram for the F20? I have a bunch of disconnected wires. I have a PDF manual for the F20/F50 printed 1990, but the wiring info is only very basic.

Thanks for reading!

[Ammann]

I got a look at another F20. It had a yellow wire on the sender between thermostat and radiator, and a yellow/green wire on sender between thermostat and engine.

[Sookie]

I had same kinda thing happen to my f20 scat , myn had 2 senders as well,
I ended up just putting 3 after market gauges in where the stock 3 where in the Center temp oil and volts myn was a deluxe one