RELAY CIRCUIT TEST
For circuit descriptions and diagrams, refer to Air
Conditioning/Heater in Wiring Diagrams.
(1) The relay common feed terminal cavity (30) is
connected to fused battery feed directly from a fuse
in the Power Distribution Center (PDC), and should
be hot at all times. Check for battery voltage at the
PDC cavity for relay terminal 30. If OK, go to Step 2.
If not OK, repair the open circuit to the PDC fuse as
required.
(2) The relay normally closed terminal cavity (87A)
is not used for this application. Go to Step 3.
(3) The relay normally open terminal cavity (87) is
connected to the blower motor. When the relay is
energized, terminal 87 is connected to terminal 30
and provides full battery current to the blower motor
feed circuit. There should be continuity between the
PDC cavity for terminal 87 and the blower motor
relay output circuit cavity of the blower motor wire
harness connector at all times. If OK, go to Step 4. If
not OK, repair the open circuit to the blower motor
as required.
(4) The coil battery terminal cavity (86) is con-
nected to the ignition switch. When the ignition
switch is placed in the On position, fused ignition
switch output is directed from a fuse in the junction
block to the relay electromagnetic coil to energize the
relay. There should be battery voltage at the PDC
cavity for relay terminal 86 with the ignition switch
in the On position. If OK, go to Step 5. If not OK,
repair the open circuit to the junction block fuse as
required.
(5) The coil ground terminal cavity (85) is con-
nected to ground. This terminal supplies the ground
for the relay electromagnetic coil. There should be
continuity between the PDC cavity for relay terminal
85 and a good ground at all times. If not OK, repair
the open circuit as required.
ADDITIONAL RELAY CIRCUIT TESTING
• The relay common feed terminal cavity 30 is
connected to the low side of the blower motor. When
the blower switch is Off and the ignition is On, there
should be battery voltage present on this circuit.
When the ignition switch is On, the voltage at that
point should vary based on blower switch position.
• The normally closed contact cavity 87A is con-
nected to the resistor block cavity 3. Check this cir-
cuit by turning the blower switch to High and cycling
between Heat and A/C modes. The voltage in the
Heat mode should be approximately 2 volts. The
blower switch must be in High blower speed position
during this check.
• The normally open contact on cavity 87 is tied to
both the resistor block cavity 6 and the HVAC blower
switch cavity 6. Check for continuity on this circuit.
• The coil B+ contact cavity 86 is connected to an
ignition run start feed. Battery voltage should be
present on this circuit when the ignition switch is in
the Run position.
• The coil ground (–) cavity 85 is connected to the
HVAC switch cavity 2 as well as the JTEC and A/C
high pressure switch. Battery voltage should be
present on this circuit when the ignition switch is in
the Run position and a Heat mode is selected on the
control head. When an A/C mode is selected, the volt-
age at this point should be less than 1 volt.
• If the blower motor does not operate, or only
operates in some modes, check for a faulty connection
at the VRR, or defective blower motor relay (VRR).
BLOWER MOTOR RESISTOR
Both the front blower motor resistor and the
optional rear overhead A/C unit blower motor resistor
can be diagnosed using the procedure that follows.
For circuit descriptions and diagrams, refer to 8W-42
- Air Conditioning/Heater in Group 8W - Wiring Dia-
grams.
WARNING: ON VEHICLES EQUIPPED WITH AIR-
BAGS, REFER TO GROUP 8M - PASSIVE
RESTRAINT SYSTEMS BEFORE ATTEMPTING ANY
STEERING WHEEL, STEERING COLUMN, OR
INSTRUMENT PANEL COMPONENT DIAGNOSIS OR
SERVICE. FAILURE TO TAKE THE PROPER PRE-
CAUTIONS COULD RESULT IN ACCIDENTAL AIR-
BAG DEPLOYMENT AND POSSIBLE PERSONAL
INJURY.
(1) Disconnect and isolate the battery negative
cable.
Fig. 7 Blower Motor Relay (VRR) Location
1 – BLOWER MOTOR RESISTOR CONNECTOR
2 – BLOWER MOTOR RELAY
3 – BLOWER MOTOR CONNECTOR
4 – GLOVE BOX LAMP CONNECTOR
24 - 16 HEATING AND AIR CONDITIONING DN
DIAGNOSIS AND TESTING (Continued)
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