GMC MOTORHOME 1978 User manual

A Word To
The
GMC Motorhome Owner ...
Congratulations on your purchase of a GMC Motorhome . You have
opened the way to an endless variety of
happy holidays .
This manual has been prepared to acquaint you with the operation
and maintenance of your Motorhome, and to provide important safety
information . It is supplemented by two convenient folders which provide
additional information on vehicle maintenance and warranties . We urge
you to read these three publications carefully . Follow the recommen-
dations to help assure the most enjoyable and troublefree operation of
your vehicle .
While reading this manual you will notice that some specifications
are given in both metric and customary units . Where
precise accuracy is
not needed, some conversions have been
rounded to even numbers for
your handy use .
An Operating Manual Appendix
is
provided with
vehicles
built
after
January 1, 1978, which have
a gross vehicle weight rating (GVWR) in
excess of 10,000 pounds . This
Appendix covers items relating to com
pliance with Federal noise
emission standards and includes the noise
emission
warranty . It also contains information on maintenance of the
noise control system
and lists acts which are considered to be tampering
with the system . As noted
in the Appendix, tampering with the noise
control system is prohibited by
Federal Law .
When it comes to service, remember
that your GMC Motorhome
Dealer knows your vehicle best .
Your
dealer is
interested in your com-
plete satisfaction . Return to him for Guardian
Maintenance Service and
any other repairs you may require .
To assist dealers in
handling your needs GMC Truck and Coach
maintains a
number of Zone Offices throughout the country . If you have
a problem that has not been
handled
to
your satisfaction, please follow
the procedure described under the
"Owner Assistance" section .
Thank you for choosing
a
GMC
Motorhome . We extend our best
wishes for many years of pleasant traveling .
Cordially,
General Sales
Manager

1978
GMC
MOTORHOME
OPERATING
MANUAL
IMPORTANT
This manual should be considered a
permanent
part of the vehicle . It should remain
with the
vehicle when sold, to provide the next owner
with
important safety, operating and
maintenance
information .
All information, illustrations and specifications
contained in this manual are based on the latest
product
information available at the time of
printing
. The right is reserved to make changes
at any
time
without notice .
For
vehicles sold in Canada, substitute the
name General Motors of Canada Limited when-
ever the
name GMC Truck & Coach Division
appears in this manual .
Service Publications
GMC TRUCK & COACH DIVISION
GENERAL MOTORS CORPORATION
Pontiac,
Michigan 48053
X-7821 A
Part No . 2028572

TABLE OF CONTENTS
SUBJECT
PAGE NO . SUBJECT
PAGE
NO .
Important
Information on
Cruise Control . . . . . . . . . . . . . . . . . 19
Vehicle Loading . . . . . . . . . . . . . . . . . . .
1
Floor Controls . . . . . . . . . . . . . . . . ..
. 21
Before Driving Your Motorhome . . . . . . . . .
3
Power Brake System . . . . .. ...
. . . 21
Driver Checklist . . . . . . . . . . . . . . . . . .
3
Headlight Dimmer Switch
. . . . . . . . .
22
Guard Against Theft . . . . . . . . . . . . . . .
3
Headlight "Flicker . . . . . . . . ... ... .. 22
Inside Rearview Mirror . . . . . . . . . . .
. . 4
InstrumentPanel and Controls . . . . . . . 22
Outside Rearview Mirror . . . . . . . . . . .
. 4 Speedometer
and Odometer . . . . ... 22
Keys . . . . . . . . . . . . . . . . . . .
. . . . . . 4 Fuel Gauge . . . . . . . . .
. . . . . . . . . . . 22
Entrance Door . . . . . . . . . . . . . . . . . . . 4
Temperature Gauge . . . . . . . . . . . .
. 22
Seats
. . . . . . . . . . . . . . . . . . . . . . . . . . 5
Oil Pressure Gauge . . . . . . . . . . . . . .
23
Head
Restraint for Dual Passenger Seat . 8
Charging System Warning
Light
. . .
. 23
Belt Restraints . . . . . . . . . . .
. . . . . . . . 9
Brake System Warning Light . . . . . . 24
Restraint of Pregnant Women . . . .
.
.
. . 9
Tell-Tale Warning Light Cluster . . . . 24
Lap Belt Inspection . . . . . . . . . . . . . . .
10 Voltmeter . . . . . . . . . . . . . . . . . .
. . . 25
Child Restraint . . . . . . . . . . . . . . . . .
. . 10 Headlight
Switch
. . . . . . . . . . . . . .
. 25
Trailer Towing . . . .
. . . . . . . . . . . . . . . 10 Windshield
Wiper Lever . . . . . . . . . . 25
Operation
In Foreign Countries . . . . . . . 11
Windshield Washers . . . . . . . . . . . . . 25
Trip Tips .
. .
.. .
. . .
.
. . . . . . . . . . . . . 12 Fuel
Selector Switch
. ..
. . . . . . . . . . 26
Driving Tips . . . . . . . . .
. . . . . . . . . . . . 13 Battery Boost Switch . . . . . . . . . . . .
. 26
Starting and Operating
Vehicle . . . . . . . . . 15
Cigar-Cigarette Lighter . . . . . . . . . .
. 26
Engine
Exhaust
Gas
Caution . . . . . . . . 15 Automotive
Heating and Air
Conditioning System . . . . . . . . . . .
26
Steering Column Controls . . . . . . . . . .
16
Anti-Theft Steering Column Lock . . .
16
Radios and Tape Player . . . . . . . . . . 27
Guard Against Theft . . . . . . . . . . . . . 16
Mobile Radio Systems . . . . . . . . 30
Parking . . . . . . . . . . . . . . . . . . . . . . 17
Electro-Level System . . . . . . . . . . . . 30
Starting the Engine
.
. . . . . . . . . . . . 17
Operation of Living Area
Facilities . . . . . . . 33
New Vehicle "Break-In" Period . . . . . 17 Living Area Facilities Caution . . . . . . . 33
Automatic Transmission . . . . . . . . . . 18
Living Area Electrical System . . . . . . . . 33
Turn Signal Lever
. . .
. . . . . . . . . . . 18
General Information
. . . . . .
.
..
. . . . 33
HazardWarning Flasher . . . . . . . . . . 19
120-Volt
To 12-Volt
Converter
Horn Control . . . . . . . . . . . . . . . . . . 19
and Battery Charger . . . . . . . . . . 34
Power Steering
. . . . .
. . . . . . . . . . . . 19 External Power . . . . . . . . . . . . . . . . .
34
Tilt Steering
Wheel . . . . . . . . . . . . . 19 Lighting System . . . . . . . . . . . . . . . . 35

SUBJECT

PAGE NO .
Monitor Panel
. . . . . . . . . . . . . . . . . 35
Motor
Generator . . . . . . . . . . . . . . . 36
Exterior
Receptacle . . . . . . . . . . . . . 37
Living Area WaterSystem . . . . . . . . . .
38
Filling Water Tank . . .
. . . . . . . . . . 38
External Water Connection . . . . . .
. 38
Water Pump . . . . . . . . . . . . . . .
. . . .

39
Water Heater . . . . . . . . . . . . . .
. . . .
40
Kitchen
Facilities . . . . . . . . . . . . . . . . . 41
All-Electric Refrigerator . . . . . . . . . . 41
PowerRange
Hood . . . . . . . . . . . . . 42
L .P . Gas
Kitchen Range/Oven . . . . . 42
L .P .
Gas Cook Top . . . . . . . . . . . . . . 44
Microwave
Oven . . . . . . . . . . . . . . . 45
Kitchen Sink and Faucet . . . . . . . . . .

54
Water Treatment Unit . . . . . . . . . . . 55
Bathroom
Facilities . . . . . . . . . . . . . . . 55
Standard
Toilet
. . . .
. . . . . . . . . . . . 55
Recirculating Toilet .
. . . . . . . . . . . . 56
Bathroom Sink and
Shower Control Valve . . . . . . . . . .

5 7
Bathroom Warm Air Duct . . . . .
. . . .

5 7
Bathroom Exhaust Vent and
Fan . . . . 57
Ventilation . . . . . . . . . . . . . . . . . . . . . . 58
Windows . . . . . . . . . . . . . . . . . . . . . 58
Ceiling Vents . . . . . . . . . . . . . . . . . . 59
Roof-Mounted Air Conditioner . . . . . . .
60
Emergency Starting .. ..
. . . . . . . . . . . 71
Jump Starting . . . . . . . . . . . . . . .
. . . . 71
TABLE OF
CONTENTS
SUBJECT

PAGE NO .
Engine Coolant . . . . . . . . . .
. . . . . . . . .
73
Engine
Coolant Caution . . . . . . . . . . . . 73
Jack Usage Instruction . . . . . . . . . . . . . 74
Towing . . . . . . . . . .
. . . . . . . . . . . . . . . 76
Freeing Vehicle
From Sand, Etc . . . . . . .

77
Rear Suspension
Failure . . . . . . . . . . . . 77
Emergency Exit . . . . . . . . . . . . . . . . . .
78
Fire Extinguisher . . . . . . . . . . . . . . . . .
79
Appearance Care . . . . . . . . . . . .. . .
. . . . 81
Care and Cleaning of Interior . . . . . . . . .

81
Cleaning Fabrics
(With Foam-Type Cleaner) . . . . . 81
Cleaning Fabrics
(With Solvent-Type Cleaner) . . . .

82
Removal of Specific Stains . . . . . . . . .

82
CleaningLeather or Vinyl
Trim
. . . .

82
Seat Belt Care . . . . . . . . . . . . . . . . .
82
Glass

Surfaces . . . . . . . . . . . . . . . . . .

82
Vacuum
Cleaner
. . . . . . . . . . . . . . . .
84
Draperies . . . . . . . . . . . . . . . . . . . . .
85
Kitchen Sink . . . . . . . . . . . . . . . . . . .

85
Power Range
Hood Filter . . . . . . . . . 85
L .P . Gas Range/Oven . . . . . . . . . . ..
85
L .P . GasCook Top . . . . . . . . . . . . . .

86
Microwave Oven . . . . . . . . . . . . . . . 86
Exterior Appearance Care . . . . . . . . . . .
86
Washing . . . . . . . . . . . . . . . . . . . . . .
86
Cleaning White
Sidewall Tires . . . . . . 87
Underbody Maintenance . . . . . . . . . . 87
Furnace . . . . . . . . . . . . . . . . . . . . . . . . 61
Polishing and Waxing . . . . . . . . . . .
. 86
Protection of Exterior
Furniture . . . . . . . . . . . . . . . . . . . . . . .
63
Bright Metal Parts . . . . . . . . . . .
. 87
In
Case of Emergency . . . . . . . . . . . . . . . . 71
Foreign Material Deposits . . . . . . . . . 87
Four-Way Hazard Warning Flasher . . . . 71 Finish
Damage . . . . . . . . . . . . . . . . . 87

SUBJECT

PAGE NO .
Undercoating . . . . . . . . . . . . . . . . . . 87
GM Appearance Care and
Maintenance Materials . . . . . . . . . 88
Service and Maintenance . . . . . . . . . . . . . . 89
Maintenance Schedule
. . . . . . . . . . .
. . 89
NIASE Mechanic Certification . . . . . . . 89
Accessibility
. . . . . . . . . . . . . . . . . . . . .
90
Exterior Compartments . . . . . . . . . .
90
Engine Accessibility . . . . . . . . . . . . . 93
Engine Compartment Light . . . . . . . .

93
Hoisting Instructions . . . . . . . . . . . . . . .
93
Lubrication Details . . . . . . . . . . . . . . . .
94
Engine . . . . . . . . . . . . . . . . . . . . . . . 94
Transmission . . . . . . . . . . . . . . . . . .
96
Final Drive . . . . . . . . . . . . . . . . . . . . 97
Steering System . . . . . . . . . . . . . . . .
98
BrakeSystem . . . . . . . . . . . . . . . . . . 98
Servicing Details
. . . . . . . . . . . . . . . . . .
99
Engine Cooling System . . . . . . . . . . . 99
EngineFuel System . . . . . . . . . . . . .
101
Carburetor . . . . . . . . . . . . . . . . . . .
.102
Engine
Air Cleaner . . . . . . . . . . . . . . 102
Chassis
Electrical System . . . . . . . . . 102
Wheels and Tires
.
. . . . . . . . . . . . . . 104
Wheel Bearings
. . . . . . . . . . . . . . . . 108
Front Suspension
. . . . . . . . . . . . . . . 108
TABLE OF CONTENTS
SUBJECT

PAGE
NO .
Rear Suspension
. . . . . . . . . . . . . .
. .
109
L .P . Gas System
. . .. ... . . . . . . . . .
111
Living Area Electrical System . . . . . . 112
Onan Motor Generator Maintenance . 116
Standard Toilet

. . . . . . . . . . . . . . . . 118
Recirculating Toilet . . . . . . . . . . . . . 119
Draining Holding Tank . . . . . . . . . . . 120
Draining Living Area Water System . .120
Water Tank Filter . . . . . . . . . . . . . . 121
Sanitizing Living Area
Water System

. . . . . . . . . . . . . . . 122
Winterization . . . . . . . . . . . . . . . . . .123
Vehicle Storage
.
. . . . . . . . . . . . . . . 123
Vehicle Trip Preparation . . . . . . . . . 125
General Data and Specifications . . . . . . . . . 129
Owner Assistance . . . . . . . . . . . . . . . . . . . 137
U .S . Zone Territories . . . . . . . . . . . . . . . 138
U .S . Zone Offices . . . . . . . . . . . . . . . . . . 139
General
Motors Overseas Offices
. . . .
. . 139
GM of Canada Limited-Zone Offices . . .
140
After-Hour Information Service . . . . . . . 141
Emergency Service
. . . . . . . . . . . . . . . . 141
Maintenance Manual
and Parts Book . . 141
Facts About Gasoline Mileage . . . ..
. .
142
Index (Alphabetical )

. . . . . . . . . . . . . . . . . 143
Gas Station Information . . Inside Back Cover

IMPORTANT INFORMATION
ON
VEHICLE LOADING
OVERLOADING
CAUTION
The components of
your vehicle are
designed to provide
satisfactory service
if the vehicle is not loaded
in excess of
either the Gross
Vehicle Weight Rating
(GVWR) or the
maximum Front and
Rear Gross Axle Weight
Ratings
(GAWR's) . yThese
ratings are listed on
the Vehicle Identification
Number (VIN)
plate located behind the
right front
access door
. - Overloading can
create
serious potential safety hazards
and
shorten
the service life
of
your
vehicle .
Your dealer
can advise you concerning
proper
loading conditions of
your vehicle .
When loading the
Motorhome, it is impor-
tant that
it is properly loaded .
All items should
be
loaded as centrally and as low
as possible .
This is essential to maintain
proper vehicle
handling . Even though a single item
may not
weigh much
alone,
several
of these
items may
have considerable weight . Proper loading is
essential .
MAXIMUM FRONT AND REARAXLE
WEIGHTS (AS MANUFACTURED)
The weight of the cargo load must be properly
distributed over both the front and rear axles .
The VIN plate shows the maximum weight that
the front axle can carry (front GAWR) and
the maximum weight that the rear axle (rear
GAWR) can carry . The GVWR represents the
maximum
permissible loaded weight of the vehi-
cle and takes
into consideration the engine,
transmission, frame,
suspension, brake, axle and
tire capabilities . Actual
front and rear end
weights can only bedeterminedby weighing
the
vehicle . This
can be accomplished through high-
way weigh
stations or other such commercial
facilities .
Consult your dealer for assistance . The
cargo load should be
distributed on both sides
GVWR RATING 12,500 LBS .
FRONT GAWR
4,500 LBS
.
REAR
GAWR
8,000 LBS .
MAXIMUM TOTAL WEIGHT AT GROUND 12,500 LBS .
*Curb weight is the maximum weight of the vehicle without
driver, passengers, or cargo,
and empty fresh water, LP, and holding tanks, but does
include fuel and coolant .
Vehicle Loading
1

of the
centerline of the vehicle as equally as
possible .
ALLOWABLE LATERAL
WEIGHT
VARIATION
The independent suspension
on this vehicle could
be adversely affected byan
unbalanced load on
either side of vehicle .
The allowable front lateral
weight variation is 250
pounds . The allowable
rear lateral weight
variation is 600 pounds .
Lateral
weight variations in excess of
the
above,
can result in abnormal vehicle
handling .
VIN (Vehicle
Identification Number)
Plate
Your VIN plate shows
the GVWR and the front
and rear GAWR's for your
vehicle .
GENERAL
MOTOR
CORPORATION 0 1
WARRANTY
MAY BE VOIDED
If WEIGHT EXCEEDS ANY OF RATINGS
SHOWN . GROSS
VEHICLE WEIGH T INCLUDES WEIGHT OF BASE VEHICLE, ALL ADDED EQUIPMENT, DRIVER
AND PASSENGERS, AND ALL PROPERTY
LOADED INTO OR ONTO VEHICLE
.
GROSS
VEHICLE WEIGHT FOR THIS VEHICLE
MAXIMUM FRONT END
WEIGHT ATGROUND
MAXIMUM REAR END WEIGHT
AT GROUND
VEHICLE IDENTIFICATION NO .
RATINGS IN POUNDS - AS
MANUFACTURED
Vehicle Identification
Plate
EFFECT ON WARRANTY
TIRES
For continuing
satisfaction keep your vehicle all
GM . General Motors Parts are
identified by one
of these
trademarks :
D
V
Delco
Gross Vehicle Weight (GVW) is the weight
of the originally equipped vehicle and all items
added to the vehicle after it has left the factory .
This would include the driver and all occupants,
and everything that is loaded into (or onto) the
vehicle . The GVW must not exceed the GVWR
.
Also, the front and rear weights of the loaded
vehicle must not exceed the front and rear
GAWR's .
CAUTION
Luggage
or
other cargo should be
secured in place, This will help keep
such
things from being
thrown about
and injuring
people
in
the vehicle in
accident
.
Your New Vehicle Warranty does not apply
to
any part of your vehicle "which has been subject
to misuse ."
Any part which fails because of over-
loading has been subject to misuse .
The tires on your vehicle
should
be
of the proper
size
and be properly inflated . It is important to
avoid over-inflation
as well as under-inflation .
See the
SERVICE AND MAINTENANCE sec-
tion for proper tire inflation pressures .

BEFORE DRIVING YOUR MOTORHOME
DRIVER CHECK
LIST
BEFORE ENTERING VEHICLE
1 . See that windows, mirrors, and lights are
clean .
2 .
Check whether any tire is low or flat . (You
may need to check wtih a gauge to tell
if
radial tires are
properly
inflated .)
3 . Check that all exterior
lights work .
4 . Look for fluid leaks .
5
.
Turn off LP gas valve on LP tank (See
CAUTION
under "LP Gas System" in SER-
VICE AND
MAINTENANCE section) .
6 . Check that
sewer connection, all external
compartments, and filler openings are
prop-
erly stowed or closed and/or locked .
7 .
Check that items stored on exterior of ve-
hicle are
securely lashed .
8 . Will any items stored on exterior of vehicle
present a clearance problem?
9 . Are there any rocks, posts,
low-hanging lines
or branches under or near the
vehicle you
must avoid before driving away?
10 . Check area behind vehicle if about to back-
up .
BEFORE DRIVING OFF
1 . Lock entrance door .
2 .
Check that all windows are in suitable
position for travel (See
"Engine Exhaust
Gas Caution (Carbon Monoxide) " at the
beginning of STARTING AND OPER-
ATINGVEHICLE section .) Close all roof
vents .
3 .
Turn off living area water pump .
4 . Check that refrigerator door is fastened .
5 . Check that nothing heavy is stored in over-
head or high cabinets-it may fall out
en-
route
and
cause injury . Be sure the gun,
ammunition, and fishing equipment cabinets
are locked, if vehicle is so equipped .
6 . Close and secure bathroom, closet, and all
cabinet doors and drawers .
7 . Check that counter tops, range top, kitchen
sink,
table tops and shelves are
clear-even
small items may become projectiles in an
accident . It is not safe to cook while under-
way-hot food or liquid may scald in a sud-
den stop or accident .
8 . Be sure all LP gas controls on furnace,
range/oven and gas/electrical refrigerator
(if so equipped) are turned off .,
9 .
Check
that
all interior stowage is securely
held .
10 . Check that all lights and switches are set in
positions suitable for travel .
11 . Adjust driver's seat for comfort .
12 . Check that driver's and front passenger's
seat, and any other swivel-mounted seats
are locked in position .
13 . Adjust inside and outside mirrors . Adjust
curtains where
necessary for visibility .
14 . If vehicle is equipped with optional
Electro-
Level System II, check that TRAVEL
switch is positioned in "AUTO" . Switch
should be moved to "HOLD" after 5 minutes .
15 . Fasten belt restraints .
16 . Check that warning light bulbs light when
key is turned to "ON" or "START" position .
17, Check all gauges .
18 . Release parking brake, and see that the
"PARK BRAKE" light turns off .
19 . With engine running, check that warning
lights are now out .
20 .
Be sure you know your vehicle and how to
operate it and its system and equipment
safely .
21
. It
is recommended that you refer to "TRIP
TIPS" and "DRIVING TIPS" at the end
of this section for additional information .
CAUTION
Counter and table tops should not be
used for storage when underway-even
for light weight, small articles . They
might
become
dangerous projectiles
dur-
ing an accident . Heavy items stored in
overhead or waist-high cabinets may
also cause injury if a sharp turn or stop
causes them to topple against inside of
cabinet door, forcing it open . Store
canned goods and other heavy items
down low . Be sure the gun, ammuni-
tion,
and
fishing equipment cabinets
are
locked, if vehicle
is
so equipped
.
GUARD AGAINST THEFT
For tips on how to protect your vehicle and its
contents, see the "Steering Column Controls"
section of this manual .

Inside Rearview Mirror
INSIDE REARVIEW MIRROR
The mirror can be adjusted up, down, or side-
ways to obtain the best view
to the front and
rear . Move the mirror
lever to the night position
to reduce glare from headlights of
vehicles be-
hind you .
OUTSIDE REARVIEW MIRROR
Adjust
the
outside
mirror
so
you can just see
the side of your vehicle in the side of the mirror
closest to the vehicle .
KEYS
Two different keys are provided for the locks
on your VEHICLE . The key
code is stamped
on
DOOR LATCH
Entrance Door Latch
the "knock out" plug in
each key head .
Key with square head (letter
"J")-for igni-
tion lock only .
Key with oval head (letter "K")-for all
other
locks .
For
vehicle security
" Recordkey code numbers
;
then knock plugs
out of keys
.
Keep the key codes in a safe place such as
your wallet, NOT IN THE VEHICLE .
If the
original keys are lost, duplicates can be
made using the key codes . Contact any GM
dealer or your locksmith .
If you park in an attended lot, separate and
leave your square ignition key only . Lock your
glove box (also all other compartments with key
locks) and
take the round key with you .
This
will help prevent any illegal entry into the
glove
box or any other compartments with locks .
If the refrigerator is equipped with a lock, a
third key will be provided .
ENTRANCE
DOOR
Doormust be locked from outside the vehicle
by inserting the key into the door key lock and
turning . To unlock,
turn in the clockwise direc-
tion .
Reverse the direction to lock .
To lock door from
inside
vehicle, push the
lock
button DOWN . To unlock and open door
from
the inside, pull the lock button UP and
pull on inside door handle .

Seat
Track Mechanism (Typical)
CAUTION
For safety's sake, always lock the en-
trance door when driving . This pro-
vides greater safety in accidents, and
helps keep children from opening the
door . It also helps keep out intruders
when stopped for lights, etc .
SEATS
DRIVER AND FRONT PASSENGER SEATS
The driver and front passenger seats may
be adjusted to suit an individual's preference .
To move seat forward or backward, simply re-
lease the seat locking lever located on the aisle
side of the seat . Once released, exert slight body
pressure
in
the
direction desired
.
Release lever
to lock the seat in the desired position .
The seats can be swiveled to provide easy
entrance and exit . To swivel seat, depress seat
swivel lever (as shown), then rotate seat . The
seats are designed to lock only in the forward
facing position .
CAUTION
After
adjusting a
manually
operated,
seat, push -forward and backward on
seat and twist seat to he sure the seat
adjusters
and swivel
lock have latched .
Movement
of
the seat indicates that at
least
one latch
or
the lock
did
not en-
Seat Swivel
Mechanism
(Typical)
gage . This could increase the chance of
injury and/or the amount of injury in
an accident . Take the vehicle to your
dealer for service if you find that your
seat adjusters do not latch .
Do not adjust a manually operated
driver's seat swivel or fore and aft
lever while the vehicle is moving . The
seat could move
suddenly and could
cause the driver to lose control of
the
vehicle .
Dual Passenger Seat Swivel Mechanism