I have a Pro Heat 7901 that may be similar. Suction is always on and brush always run. I think the problem may be your spray system rather than the suction. When my machine is working correctly enough water is sprayed that you need to have the suction running full time or you would soak your carpet without too much trouble. Usually with these machines the spray system gets clogged and not enough water is delivered. The clogging happens when different parts get clogged with dirt, corrosion or soap scum. The parts that generally get clogged are the spray nozzles, the connector fittings the wand or main valves, the flow indicator, the automix assembly and the heater core. Sometimes the plastic tubing can also deteriorate or even get pinched if the case had been previously removed. Another possible problem is with the pump itself. If you notice that the brush is not spinning, it might also be a belt issue.
Other than surface cleaning the spray nozzles, which can be done easily, the other items would probably require some dismantling of the machine. If you find that the problem is actually with a lack of fluid being delivered, there is a lot of information available online for a wide range of models.
Kim, January 2017
