89 , no heat

This is a new car to me and all the controls appear to be working fine and the AC works and the fan works fine.

It only ever blows cold air. I did feel both heater hoses and they are hot. The temp and thermostat seems to be working fine as indicated on the temp gauge.

What would be the first step to diag the temp slider control on the dash? It seems to feel fine , but makes no noise or difference. Possibly it is a vacuum control?

Thanks for this ford help.

It was the cable had popped off of the control arm. Mechanic snapped it back on.