I have a 1981 Civic 1500. A part broke off and I don't know what it is to replace it. It has three blue wires coming out of it and a connector on the end that plugs into a wiring harness. The other end is bolted into the cylinder head on the battery side of the engine. Pics attached. Does anyone know what this part is??

 

Looks to be the coolant thermo-switch, #20 in this parts diagram. Part of it is broken off.

https://www.hondapartscheap.com/v-19...erature-sensor

 

That looks right, and my car did have CA emissions. Now the question is, will having this part broken stop the car from getting power? The battery is good, voltage is good at the main fuse and the starter, but when I turn the key I get no dash lights and no start, just nothing.

 

Please, post a picture of your car. I had a co-worker back in the 80's who drove a brown Honda Civic like yours. Would love to see how your Civic looks after all these years. Thanks

 

That part would not stop the car from getting power.

If the dash lights doesn't even turn on, check if power is at the ignition switch wires (electrical switch). If there is power going to the ignition switch; but, not going through it when turned to the ON/RUN position, then the cause may be with the ignition switch.

 

This is the newest picture I could find. I did have it painted once at one of those cheap paint job places, but all the rust came back through in a year.