garage door motor?

(1) Why exactly do you want to know the motor voltage? If it's to select a key switch with an adequate rating (e.g. a choice between a 240 V switch and a 12 V switch) then just go for the higher rating - 240 V say. Using that for a 12 V system won't do any harm.
(2) Check the cable feeding the motor. The outer sheath/insulation will have a code and voltage etc either printed or embossed on it.
(3) What kind of motor is it? The most common type of a.c. motor (at least in small domestic type appliances etc) is a single phase induction motor. These are usually capacitor start/run motors. They can be identified by a bulge on the motor casing which houses the capacitor. This kind of motor needs alternating current (a.c.) to run - i.e. mains.
If it was to operate from a lower voltage (Say 110 V) there would have to be a transformer to step it down from mains voltage (assuming you are in UK or Ireland - 240V) and this should be easily identifiable.
(4) If you know what current (I) it draws (if you don't- what size fuse or circuit breaker has been protecting up until now?), you could measure the resistance (R) with an ohmeter (multimeter) and V= R x I. (A few simplifications made there but should give a good enough answer).

J
November 2009

Prior discussion on this site...

http://www.howtomendit.com/answers.php?id=115117

Are you sure the brand is "Rollaway" ?

Page 19 of this pdf might be useful (but might not be)

http://www.liftmaster.de/produkte/download/bas300k.pdf

Found at...
http://www.easygates.co.uk/liftmaster-manuals.asp#garage_door_openers

Size of cable indicates Current rather than Voltage

Does it work if there's a power failure i.e. are there back-up batteries to work the door?

What components are on the control board where the motor wires connect?

Is there a motor start capacitor (AC motor) in the circuit?

Have you considered repairing the defunct control panel?

Your need for a new remote control unit confuses when you say the control panel is defective.

A home engineered solution with just a simple switch might be dangerous without safety devices built in.

I know nothing of electrically operated garage doors.

Good luck...

Peccavi
November 2009