Reversible electric motor - what am I looking at?

[Nugatory]

TL;DR

What are these components on my reversible motor and how is the whole thing supposed to work?

I have a reversible electric motor that operates an automatic skylight, vintage 1985. I'm trying to figure out how it is supposed to work, but I don't recognize the rectangular gray components that are secured to the motor case with a length of plastic zip-tie. What might they be and how would the whole thing work?

 

[Baluncore]

They are 27 ohm power resistors, probably to limit maximum motor current = torque.

 

[Wrichik Basu]

I don't recognize the rectangular gray components that are secured to the motor case with a length of plastic zip-tie

They look like fusible cement resistors, $27~\Omega,\ 9~\mathrm{W}$ with $5\%$ tolerance.

Edit: @Baluncore beat me to it.

 

[Tom.G]

They look like fusible cement resistors

Probably just a typo, but I believe you are referring to Cermet.

That is a compound of cer[/size]amic and met[/size]al, which combine to give characteristics of both.

Further info: https://www.google.com/search?hl=en&q=cermet

Cheers,
Tom

 

[Baluncore]

Probably just a typo, ...

Maybe not.
I think you will find the higher power, low value resistors like those are wire wound on the inside, with a ceramic or cement case to reduce wire oxidation and fire hazard.

Cermet resistors are usually more expensive, with power 1 watt or less, higher resistance, and lower inductance.

Destructive testing would resolve the question.

The series diode is interesting. Does it provide directional control of the torque limit?

 

[Wrichik Basu]

Probably just a typo, but I believe you are referring to Cermet.

That is a compound of ceramic and metal, which combine to give characteristics of both.

Further info: https://www.google.com/search?hl=en&q=cermet

I meant cement. I bought a few of those some months back to help in my experiments. In fact, I had never heard of cermet resistors; thanks for the information.