Cruise control non op.

[Mr.green]

I have a 1978 chevy with factory cruise. it does not work.
I can put the vacuum lines off the transducer together and it will pull the arm and race the engine. The vac line is on the brake switch, wiring all looks good.

Is there something I can test? if the truck is running and I push the cruise button will I get voltage at the transducer?

I can go buy a new transducer if needed, but trying to make sure it is that before I spend 90 bucks.

Thanks.