Chevrolet 10 Series 1970 Service Manual page 40

HEATER AND AIR CONDITIONING 1A-10
OUTLET
The evaporator p ro vid es maximum cooling of the a ir
passing through the co re when the a ir conditioning sys­
tem is calling fo r cooling.
system only to control the evaporator p ressu re so that
minim um p ossib le tem peratu re is achieved without core
fre e z e -u p . The v a lv e is p re s e t, has no manual control,
is au tom atically altitude compensated, and n on-repairable.
System operation is as follow s (See F igu re 17):
eith er outside a ir o r re circu la ted a ir enters the system
and is fo rc e d through the system by the blow er.
The a ir passes by the tem peratu re door and is d irected
through the heating o r cooling c ores, o r sp lit to flow
through both. A fte r flow in g through the co re o r c ores,
the a ir passes the outlets door which d irects it to the
dash o r flo o r outlets o r both.
ou tlets is fin a lly con trolled by the position of the a ir
ou tlets. A ir d irected to the flo o r outlets passes the
d e fro s te r door which d ire c ts the a ir out the flo o r outlets,
the d e fro s te r outlets, o r both.
Linkage is so designed that when the system controls
a re ca llin g fo r heat, a ir w ill enter the veh icle through the
flo o r d istrib u tor duct, and when the system controls call
fo r coolin g, a ir w ill enter through the three dash outlets.
T h e side dash outlets may be rotated to p rovid e eith er
soft, diffused a irflo w o r spot cooling.
shut o ff a irflo w . The b a r r e l type outlet in the center of
the dash w ill d ire c t a ir up o r down o r, if d esired , shut it
off.
CONTROLS
Full control of the Four-Season System is obtained
through the use of a single control panel (fig. 16).
con trol le v e r s make use of bowden cables to activate the
F ig . 17—A ir flo w S chem atic
The control valve acts in the
A ir ,
A ir d irected to the dash
Rotate half way to
The
va riou s doors and sw itches n ecessary fo r system op era­
tion. C ontrol adjustment is a m atter of p ro p e rly setting
these bowden cables. The follow in g paragraphs explain
each control.
" O u tle t" Lever
T h is le v e r actuates an a ir d iv e rte r door within the duct
assem b ly which routes a irflo w when fu lly right (H E A TE R )
to the flo o r distributor ducts (fo r heater operation) o r
when fu lly le ft (A/C) to the dash outlets
op eration ).
M oving this le v e r toward the le ft fro m the H E A TE R
position w ill activate the com p ressor clutch switch and
set the cooling portion of the system in operation p ro ­
vid in g the F A N switch is turned on.
When the le v e r is m oved fu lly toward the righ t (heating
position) the A IR control le v e r w ill autom atically move
to the outside a ir position.
Tem perature Lever
The "T E M P E R A T U R E " le v e r , through its bowden cable,
actuates the door which controls outlet tem perature.
T h is door is necessary to p erm it m ixing of hot and cool
a ir to provide the d esired conditioned a ir outlet tem p era ­
ture, whether during heating o r cooling operations.
The tem perature door
eith er the heater core, the evaporator core o r through
both. When the system is set fo r fu ll cooling, a ll a ir
p asses through the evaporator core.
le t a ir is d esired, the tem peratu re door is m oved by the
tem peratu re le v e r so that som e a ir passes through the
h eater core. The warm ed a ir m ixes with the cooled a ir
resu ltin g in a higher outlet a ir tem peratu re.
H O T position, all a ir flow s through the heater core.
(fo r cooling
d ire c ts the a irflo w through
When w a rm er out­
In the full
F o r
CHEVROLET TRUCK SERVICE MANUAL