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R
U TTW SERVICE PROCEDURE VI
Blower Temperature Switch Testing
and Replacement
Blower Temperature Switch
Testing.
Step 1.
Position gas control power switch
to the "OFF" position.
Step 2.
Remove the three screws (Phillips
screw driver) from control access
cover on blower and remove cover
(see photos 17 and 18).
Step 3.
Locate blower temperature switch
(see photo 19).
Switch Setting
Opens on rise @ approximately 165°F
Auto resets on fall @ approximately 130°F
Cool switch to
below 130°F
Disconnect wire leads to
switch. Using a multi-meter
set to the ohms setting, is
there continuity between the
switch terminals?
Y
Reconnect wire leads and
observe heater operation. Do
exhaust gas temperatures rise
to or above 165°F?
N
Do switch contacts
open?
N
Switch OK
Page 24
24
N
Replace switch
(see page 25).
N
Y
Y
Do switch contacts
open?
Replace switch
Y
(see page 25).
115 volt potential exposure. Use caution
to avoid personal injury.
Gas Control shown in the "OFF" position
17
Control Access
Cover Screws
19
Blower temperature
Air mixing inlet
Exhaust
1. Vent length is below minimum allowable.
2. Vent diameter not to specification.
temperature is too
hot.
3. Restricted dilution air inlet.
4. Missing or deteriorated flue baffle.
5. Gas pressure is out of specification.
WARNING
switch location
Common causes for
high exhaust temperature
18
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