Electrolux / Dishlex DX302 rinse aid problem?

Our Electrolux / Dishlex DX302 has a mind of it's own. Sometimes it won't heat, other times the heat is there but everything is wet. We've presumed not enough rinse aid is being dispensed. There is a simple switch to control the volume dispensed where you add the rinse aid but the level doesn't seem to drop ie nothing being dispensed. We're wondering where within the dishwasher the rinse aid is dispensed so we can see whether it is blocked. Does anyone know where this is located and/or how to overcome such a problem. Regards.