Chevrolet 1980 Light Duty Truck Service Manual page 32

1A-4 HEATER
Temperat ure o f h e a t e r a i r a t o u t l e t s too low t o h e a t up pa s ­
se nge r compart ment .
Temperature o f h e a t e r a i r a t o u t l e t s a d e q u a t e b ut t he v e h i c l e
wi l l not b u i l d up s u f f i c i e n t h e a t .
I na de q ua t e d e f r o s t i n g a c t i o n .
I nadequat e c i r c u l a t i o n o f heat ed a i r t hr ough v e h i c l e .
E r r a t i c h e a t e r o p e r a t i o n .
Hard o p e r a t i n g o r broken c o n t r o l s .
DIAGNOSIS
TROUBLE
CAUSE AND CORRECTION
1. See " I n s u f f i c i e n t Heat D i ag n o s t i c Cha r t ".
Check f o r body l e a k s such as:
1. Fl oor s i d e ki ck pad v e n t i l a t o r s p a r t i a l l y open.
2. Leaking grommets i n das h.
3 . Leaking welded seams al ong r o c k e r panel and w i n d s h i e l d .
4 . Leaks t hr ough a c c e s s hol es and screw h o l e s .
5. Leaking r u b b e r mol di ng around door and windows.
6. Leaks bet ween s e a l i n g edge o f bl ower and a i r i n l e t as sembl y
and d a s h, and between s e a l i n g edge o f h e a t e r d i s t r i b u t o r
assembl y and das h.
1. Check t h a t DEFROST l e v e r c o m p l e t e l y opens d e f r o s t e r door
i n DEF p o s i t i o n - A d j u s t i f n e c e s s a r y .
2. I n s u r e t h a t t e mp e r a t u r e and a i r door s open f u l l y - A d j u s t .
3. Look f o r o b s t r u c t i o n s in d e f r o s t e r d u c t s - Remove any
o b s t r u c t i o n s .
4 . Check f o r a i r l ea k i n d u c t i n g bet ween d e f r o s t e r o u t l e t on
h e a t e r as sembl y and d e f r o s t e r d u c t under i n s t r u m e n t panel -
Seal a r e a as n e c e s s a r y .
5. Check p o s i t i o n o f bottom o f nozzl e to h e a t e r l o c a t i n g t a b -
Ad j u s t .
6. Check p o s i t i o n o f d e f r o s t e r noz z l e o p e ni ngs r e l a t i v e t o i n s t r u ­
ment panel o p e n i n g s . Mounting t a b s p r o v i d e p o s i t i v e p o s i t i o n
i f p r o p e r l y i n s t a l l e d .
1. Check h e a t e r a i r o u t l e t f o r c o r r e c t i n s t a l l a t i o n - R e i n s t a l l .
2. I n s p e c t f l o o r c a r p e t to i n s u r e t h a t c a r p e t l i e s f l a t under
f r o n t s e a t and does not o b s t r u c t a i r f l ow under s e a t , and
a l s o i n s p e c t around o u t l e t d u c t s to i n s u r e t h a t c a r p e t i s
well f a s t e n e d t o f l o o r to p r e v e n t cuppi ng o f a i r fl ow - C o r r e c t
as n e c e s s a r y .
1. Check c o o l a n t l e v e l - F i l l t o pr op e r l e v e l .
2. Check f o r ki nked h e a t e r hoses - r e l i e v e ki nk s o r r e p l a c e h o s e s .
3. Check o p e r a t i o n o f a l l bowden c a b l e s and door s - Adj u s t as
n e c e s s a r y .
4 . Sedi ment in h e a t e r l i n e s and r a d i a t o r c a u s i n g en g i n e t her mo­
s t a t to s t i c k open - f l u s h system and c l ea n o r r e p l a c e t her mo­
s t a t a s n e c e s s a r y .
5. P a r t i a l l y plugged h e a t e r c o r e -
1. Check f o r l oo s e bowden c a b l e t a b screws o r m i s - a d j u s t e d bowden
c a b l e s - C o r r e c t as r e q u i r e d .
2. Check f o r s t i c k i n g h e a t e r syst em d o o r ( s ) - L u b r i c a t e as r e q u i r e d
us i ng a s i l i c o n e s p r a y .
b a c k f l u s h c o r e as n e c e s s a r y .
LIG H T T R U C K S ER V IC E M AN UAL