or test buzzer through the white and the red and white leads A direct circuit should always be present since the overheat switch opens only at a high temperature If there is no circuit the overheat switch should be replaced I Purge Switch A properly operating purge switch should allow the combustion blower to start immediately when the blower is turned on and after the blowers have operated for one minute should allow the combustion blower to continue to run for up to 2 minutes after the car ignition or heater switch is turned off If the combustion blower does not operate as described replace the purge switch If the motor does not operate at all check all 3 terminals of the purge switch with a test light Current should be available at all three terminals If current is present at the red and blue terminal and not at the black terminal the switch is defective and must be replaced If no current is available at the red and blue terminal check for complete circuit continuity If necessary contact points may be cleaned with a piece of smooth lint free non abrasive paper J Heater Control Switch There are three terminals on the heater control switch mounted in the air distributor When switch is in low position two terminals are hot When switch is in high position all three terminals are hot Check continuity by placing test lamp or similar testing device between each switch terminal and ground K Fuel Supply Fuel is supplied from the engine fuel system by means of a fitting installed at the fuel pump cross fitting A pressure regulator which resembles a tee fitting is located on the underbody below the front seat and near the fuel junction The leg of this tee should be horizontal or above the horizontal to properly vent vapor or bubbles through the by pass line The heater fuel pressure should be between 41 z and 5 psi for proper heater operation Check fuel pressure at the fuel line connection to the heater assembly If the pressure is lower than 41 z psi and all lines are clear the engine fuel pump probably requires repair or replacement Check fuel pump by attaching gauge to the fuel pump after the outlet fuel line has been removed and the heater fuel supply line blocked off If the fuel pump pressure is satisfactory but the heater fuel pressure is not up to specifications replace or clean and adjust the regulator The fuel flows through the heater fuel line pressure regulator heater case and into the burner assembly If this fuel line is kinked or damaged fuel delivery may be reduced which prevents the heater from operating properly The fuel line connection at the burner assembly should be tight and must not leak A leak at this point will cause raw gas fumes to be drawn inside the car by the ventilating air If it seems necessary to clean and adjust the regulator proceed as follows 1 Remove overflow fuel line at pressure regulator T NOTE Take all necessary precautions to prevent fire when gasoline is exposed 2 Remove the staked in adjusting screw counting the number of turns 3 Remove spring and nylon disc NOTE It may be necessary to tap regulator valve with a wooden block to remove nylon disc 4 Clean edges of disc until it falls freely past threaded section of regulator 5 Reassemble regulator installing adjusting screw to the same depth 6 Install fuel pressure gauge as stated previously Place pan under T to catch gasoline 7 Start engine turn adjusting screw in or out until fuel pressure is 4 5 psi NOTE Gasoline flowing out of regulator overflow outlet will wash out any chips caused by breaking the stakes 8 Turn off engine install fuel lines 9 Start engine and check for fuel leaks L Inspection of Burner The nozzle and mixer assembly should receive a special inspection after removal from the heater and before further disassembly since the condition of these parts will be an indication of the cause of unsatisfactory operation The nozzle and the inside of the mixer can around the nozzle will normally be covered with a medium layer of black carbon and the nozzle should have a small gray opening at the orifice The outer end of the mixer will usually be burned to a gray or reddish color and some scaling of loose particles may be present These are indications of normal burning and should not be considered defects Never attempt to clean a nozzle by wiping since this will force carbon into the orifice Indications of improper operation are an uneven buildup of black carbon or an excessively burned or eroded spot on the mixer The openings in the mixer cup must not be clogged with carbon since this will prevent entry of the proper amount of combustion air If this condition is present it will not be remedied by cleaning since it is caused by a one sided spray from the nozzle or by dripping or leakage around the nozzle seat The spark plug electrodes will operate properly with a considerable accumulation of carbon and lead but must not be shorted out If the electrodes are burned this indicates an improperly directed spray and the nozzle or nozzle seat is at fault Inspect the nozzle seating surface of the burner casting also the