how can I restore good suction on an Electrolux Ambassador?

There will be a leak - either in the cleaning head, the hose itself or a union joint.

Run the machine with no hose attached and listen to the noise of the motor - then attach the hose - if the motor runs faster and makes a very noticeable higher pitched sound then you have a blockage in the hose assembly. If the motor sound is much the same then you have no blockage. If the suction is much poorer at the cleaning head end then air is getting in somewhere.

Good luck...

Peccavi
January 2010