Thermostatic Air Cleaner: Testing: Notes

When this system is not working properly, the vehicle will stall or hesitate, fuel consumption will increase, and engine will seem low on power. Check all vacuum lines for connection, cracks or loose fittings and proper routing. Replace or reroute as necessary.
To check vacuum motor, stop engine and unhook fresh air duct. Using a mirror, check position of air control valve inside duct. With engine warm, fresh air inlet should be open and hot air duct closed. Check control valve linkage.
Disconnect vacuum motor inlet vacuum hose. Install another length of hose to inlet and apply vacuum through this hose to vacuum motor. With vacuum applied, again use mirror to check air control valve position. Fresh air inlet should now be closed and hot air inlet open.
With hot air inlet open (vacuum still applied), pinch vacuum hose to cut off air to vacuum motor. Air control valve should hold position for more than 30 seconds. If force of diaphragm spring overcomes vacuum and opens fresh air inlet in less than 30 seconds, replace vacuum motor assembly.