Chevrolet 70 Series 1970, Service Manual

Page: 132 / 841

CAB AND BODY MOUNTINGS 1-101
Figure 5 —System Air Flow (Conventional Cab Model)
Volum e of outside a ir entering heating sy ste m
is controlled by a dam per valve position ed at en­
tra n ce of blow er housing a ssem b ly .
NOTE: Operation of individual con trols is d e s­
crib ed in "Operating Instructions" la ter in th is
sectio n .
On Alum inum T ilt Cab M odels
The a ir flow fo rced through the evaporator
co r e and h eater co re r e su lts from the u se of a
m u lti-sp e ed blow er and m otor a ssem b ly (fig. 4).
Motor sp eed i s controlled by a fan sw itch located
on instrum ent panel.
NOTE: F or additional a ir circu lation inform a­
tion re fe r to appropriate Cab sectio n .
On Conventional Cab M odels
The a ir flow through evaporator co il and heat­
er co re is fo r ced by a sin g le blow er and m otor
unit mounted at left sid e of dash unit (fig. 5). Motor
i s con trolled by dash sw itch es.
OPERATING INSTRUCTIONS
NOTE: B efo re sta rtin g truck engine, make
su r e "AIR COND." le v e r is in "OFF" p osition to
l e s s e n the load on battery during startin g.
ALUMINUM TILT CAB
(R efer to F igu re 4)
The heating and air conditioning s y s te m s a re
con trolled by four le v e r s and a fou r-p osition fan
sw itch . A ll con trols a r e located on the co n so le to
the right of the gauge panel.
1. The A /C le v e r , when m oved to the "ON"
p o sitio n , e n e r g iz e s the co m p resso r c lu tc h -c o il to
allow refrigeran t flow through evaporator c o re.
A lso , the blow er op erates at low sp eed which r e ­
s u lts in cooling of a ir d irected through evaporator
c o r e . To obtain g r ea ter a ir flo w , u se "FAN" sw itch.
2. The "AIR" le v e r con trols the so u r c e of a ir
through sy ste m . Push knob up for outside air; push
knob down to r e circu la te in sid e a ir . Interm ediate
p o sitio n s of le v e r w ill r e su lt in a proportional
m ixture of outside and recir cu la ted a ir flow through
sy ste m .
3. The "HTR" le v e r co n tro ls the d irection of
a ir flow from sy ste m . P ush knob up to d irect a ir
flow through h eater outlets; push knob down to
d irect a ir flow through d efro ster o u tlets. Interm ed­
ia te p o sitio n s of le v e r w ill re su lt in proportional
am ounts of a ir flow through both h eater and d e­
fr o ste r ou tlets.
4. The "TEMP" le v e r d ir e c ts a ir flow eith er
around or through the main h eater c o re, o r through
both. L ever may be se t at any p osition betw een
"COOL" and "HOT" to control tem p eratu re of a ir
circu la ted through cab. If A /C le v e r is "ON” and
cab tem p eratu re is too cool for com fort, the
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCK SHOP MANUAL