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DEFROST HEATER AND THERMOSTAT
Top Mount Models
Th e s e m o d e l s u s e a r ad i a nt h e a ter to
re m o v e a c c u mu l a t e d f r ost f ro m th e
lr ee z e r e v a p o ra t o r an d d ra in tr oug h
d u ri n g a d e fr o st cy cl e .
Th e d ef ro s t t i m e r e n er gi ze s th e de fro st
h e a te r e ve ry si x or ei g h t h o urs of
a c cu mu l at e d c o m p re sso r ru n ti me . W h en
t h e t em pe ra t u re i n t h e th e rmosta t a r e a
r e ac h e s a pp r o x i m a tel y + 4 7 o F th e
t he r mos t at c o n t a ct s o pe n th e circu i t to th e
defrost heater.
Th e de f ro s t h e a te r is a sp i ra l wo u n d
r e si s t a n c e w i r e e n clo se d in a h e at
r e si s t a n t g l a s s t u b e . lt i s mou n te d i n th e
m id d l e o f t h e e v a p o ra tor be n e a th an
a l u m i n u m s h i e l d .
A n o h m m e t e r c h e c k w i l l d e t e r m i n e i f a l l
p h as es o f t h e d e f ro st cycl e ar e fun cti on in g
p ro p e r l y . T h e d e f ro st th e rmo sta t co n tacts
o pe n a t a p pr o xi ma t el y + 4 7 " F a n d cl ose
a t a p p r o x i m a t e l y + 1 5o F .
Th e d e f ro st t h e rm o sta t ma y h a ve e ith er a
4 7 K o r 5 6 K o h ms re si stor con n e cte d
in t e r na l l y a c r os s t h e tw o te rmin a l s. l f so ,
th is r e s i s t o r p e rm i t s ch ecki n g th e d e fro st
h e ater even when t he
evaporator
t e m p e r a t u r e i s * 1 5 o F o r h i g h e r .
An ohm meter can be used to test the
d e fr ost heater and ther mostat without
d isassembling the tr eezer compart ment
e ven if t he evaporat or t emperat ure is
+ 1 5o F or higher. To check proceed as
f o l l o w s :
1. Disconnect the unit f rom oow er
source.
2 . Disconnect the plug f rom t he defros t
t i m e r .
3 . Set t he ohmm eter t o t he R x 1K s cal e
and connect t he probes t o t he N o. 2
a n d N o . 3 t e r m i n a l s o f t h e d i s c o n n e c t
p l u g .
4 . The met er should read between 42K
and 63K ohms. The r esistance is not
c r i t i c a l . A s l o n g a s t h e r e i s c o n t i n u i t y
b et ween Terminals No. 2 and 3 the
def r ost
heater is
in
operativ e
c o n d i t i o n .
lf ther e is no resistance reading ( open
cir c uit) t he defrost heater and thermos tat
m u s t b e c h e c k e d i n d i v i d u a l l y . N O T E :
W h e n u s i n g t h e m e t e r a v o i d t o u c h i n g t h e
p r o b e s s i n c e t h i s c o u l d r e s u l t i n a f a l s e
r e a d i n g a n d m i s d i a g n o s i s .
4-28
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