TEST PROCEDURES-STEWART - WARNER AND HUPP HEATERS- Continued
THINGS TO CHECK
c. Apply 24.0 + 0.5vdc to module lead 6 (3).
d. Allow ten seconds for voltage at resistor or ignitor stabilize. A good module will show between 15
and 17 vdc.
Ignitor gets hot, do not touch.
e. A defective pass together will be open (resistor voltage less than 1vdc) or shorted (resistor voltage
equal to power supply voltage). This transistor should be replaced.
f. Other voltages at the resistor indicate that the module is out of adjustment since there is no provision
for adjustment; replace module.
Shut down heater, and time purge cycle.
Stewart-Warner heaters-1 to 3 1/2 minutes
Models MF510B, MF510C-2 to 3 1/2 minutes
Misadjusted flame detector switches can be quickly readjusted as follows:
1. Wait until heat exchanger is fully cooled.
2. Turn flame detector switch adjustment screw counterclockwise until blower motor stops.
Disconnect exhaust hose from heater exhaust port.
Disconnect test stand wiring harness from input connector.
Disconnect fuel supply from fuel inlet.
Install guard pages 2-32 (Hupp models); 2-42 (Stewart-Warner models).
Remove heater from test stand.
TEST ENDS HERE