24
904144 REV A 1/9/12, INST 1970-72 CUTLASS w/ AC EVAP KIT PG 24 OF 25
Symptom Condition Checks Actions
N
ot
es
S
ystem will not
turn on, or runs intermittently
.
4.
W
orks when engine is not
running; shuts off when engine is started (T
ypically early Gen IV
,
but possible on all versions).
Noise interference from either ignition or alternator
.
Install capacitors on ignition coil and alternator
. Ensure
good ground at all points. R
elocate coil and associated
wiring a
w
ay from ECU and ECU wiring. Check for burned
or loose plug wires.
V
erif
y connections on power
lead, ignition lead, and both white ground wires.
V
erif
y proper meter function b
y checking the condition of
a known good battery
.
Ignition noise (r
adiated or
conducted) will cause the system to shut down due to high v
oltage spik
es. If this
is suspected, check with a qualit
y oscilloscope. Spik
es
greater than 16V will shut down the ECU
. Install a
radio capacitor at the positiv
e post of the ignition
coil (See r
adio capacitor
installation bulletin). A fault
y alternator or worn
out battery can also result in this condition.
Will not turn on under an
y conditions.
V
erif
y battery v
oltage is
greater than 10 v
olts and less
than 16.
Loss of mode door function.
No mode change at all.
Check for damaged mode switch or potentiometer and associated wiring.
Partial function of mode doors.
Typically caused b
y
ev
apor
ator housing
installed in a bind in the vehicle. Be sure all mounting locations line up and don’
t ha
ve to be forced
into position.
Blower turns on and off r
apidly
.
6.
Battery v
oltage is at least
12V
.
Check for at least 12V at circuit break
er
.
Ensure all system grounds and power connections are clean and tight.
Battery v
oltage is less
than 12V
.
5.
Troubleshoot
ing Guide (Con
t.)
Check for fault
y battery or
alternator
.
Charge battery
.
S
ystem shuts off blower at
10V
. P
oor connections or
weak battery can cause shutdown at up to 11V
.
7.
When ignition is turned on, blower momentarily comes on, then shuts off
. This
occurs with the blower switch in the OFF position.
This is an indicator that the system has been reset. Be sure the red power wire is on the battery post, and not on a switched source. Also
, if the
system is pulled below 7V for ev
en a split second, the
system will reset.
R
un red power wire directly to battery
.
Check for positiv
e power at heater v
alv
e green wire and
blower red wire. Check for ground on control head white wire.
Check for obstructed or binding mode doors.
Check for damaged stepper motor or wiring.
Err
atic functions of
blower
, mode,
temp
, etc.
Check for damaged switch or pot and associated wiring.
R
epair or replace.
8.
Summary of Contents for 1970-72 Cutlass
Page 25: ......
