Heater System Solving Guide
FAUL
T CODE THUMBNAILS –
PAGE
F 2
FAUL
T CODE THUMBNAILS –
PAGE
F 2
Heater System Solving Guide
Fault Code Thumbnails AC
Blower V
acuum Switch – F
ailed Closed
F
AULT
C
ODE
T
HUMBNAILS
AC B
LOWER
V
ACUUM
S
WITCH
– F
AILED
C
LOSED
UHS
AC
B
LOWER
V
ACUUM
S
WITCH
– F
AILED
C
LOSED
If the blower vacuum switch is closed before blower start-up,
the control module will not start the blower.
Pre-check is executed by the control module.
P
ARTS
T
HAT
M
AY
B
E
N
EEDED
• Blower Vacuum Switch
• Control Module.
D
IAGNOSTIC
S
EQUENCE
A. Disconnect the blower plug from the control module.
With the heater off, measure the control module receptacle’s
continuity across pins 1 and 2 (UHS, IDL2 & IDL) and pins 3 & 4
(IDL2 & IDL only). If either is closed, replace the control module.
B. If the relay is open, check the vacuum switch. If it is closed,
the blower vacuum switch failed and must be replaced.
IDL
IDL2