I need to track down the wire for this sender on the bottom of the engine. I didn't see any open plugs on the engine harness or any place for a wire to pass through for this sender. Photos would work great if you have them!

Click to view attachment

That's not stock ...

My guess is it's a oil temp unit and someone didn't want to buy a factory taco plate. If that's the case, look for a green wire with a black stripe. It's part of the main harness from '73 onward and comes out of the main harness under the battery tray next to the engine shelf by the hell hole. From there it's supposed to run along the front side of the engine to the taco plate.

Looks like you have the taco plate too. It may be that the green/black Andy described is already connected... And I would have thought the one circled would be in place of the drain plug, not drilled and tapped in the sump plate.

Ya, I have the taco plate wire connected. I couldn't figure out this sender was. It must be some Rube Goldberg device. Unless the taco plate sender is bad and the DAPO rigged this one instead...

Ok, I'm changing the question.

Anyone know how to test the oil temp sender in the taco plate?

I'm starting a fresh engine and considering the wierd add on sender shown above would like to know if the factory sender is working before I over heat the engine.

The correct way to test is out of the car. Pot of hot water, thermometer and an ohm meter. Take resistance cold and every 10 degrees up to boiling. Make a graph and match the range to the gauge.

Heat it however but,,,,, Grnd to gage, grnd to sender body, then grnd to Bat......... On the positive side..........+ from bat to + on the gage and S from gage to sender post.

Click to view attachment
Probably best to remove and measure with different temps as stated above, but a measurement installed could tell if the sender is OK. I just swapped senders recently so they do go bad. Problem is, not a huge problem, but accessing the spade terminal with the cover in place. To remove the cover to get to the terminal, you have to remove the 2 - 6mm bolts which hold the base plate in place. If the base plate slips or gets bumped, it could dump the whole crankcase of oil.