Pontiac FIREBIRD 1972 Service Manual page 197

1B-10 1972 PONTIAC SERVICE MANUAL
grammer output shaft now operates normally, look
for pinched vacuum hose, loose electrical connection,
pinched or shorted Darlington Amplifier heat sink or
a mechanical bind with the programmer cover. Be
sure to tap the programmer components with the
handle of a screwdriver to check for intermittent
problems.
AMPLIFIER TEST
8. If the programmer output shaft still does not operate
properly, place the Voltage knob of the tester in the
"Probe and Clip" position. Connect the alligator clip
lead to the transducer terminal with the gray wire.
CAUTION: Do not short transducer terminals
together or arnp1i.r will be damaged.
Push the probe into the programmer connector body
making contact with terminal # 2 which connects to
a yellow wire.
9. Rotating the Manual Control knob from MAX.
HEAT to MAX COLD (or vice-versa), the voltmeter
reading should change 5 volts or more (after it is
stabilized). This change indicates that the amplifier is
"good". If the 5 volts or more change is not obtained,
check the amplifier heat sink insulator for proper
positioning. (NOTE: If the heat sink is shorted to the
programmer chassis, the programmer will go to the
full A/C position.) If the voltage change cannot be
obtained and the insulator is okay, check the calibra-
tion of the amplifier according to the instructions in
Step 18. If the programmer still does not function
properly, replace the amplifier circuit board and be
sure to install the new heat sink insulator properly.
The new amplifier must be calibrated according to
Step 18 after installation.
TRANSDUCER TEST
10. If the 5 volts change was present in the amplifier
check in Step 9 but the programmer output shaft does
not operate normally, leave the "Probe and Clip"
connected as instructed in Step 8 throughout trans-
ducer test procedure.
11. Disconnect vacuum hose from the small diameter
port of the transducer and connect tester hose from
vacuum gauge directly to this hose. About 20 inches
Hg. or more vacuum should be present on this trans-
ducer vacuum supply hose. If proper vacuum is pre-
sent, restore hose connection. If 20 inches Hg. or
more vacuum is not present, check the vacuum sup-
ply vacuum level and then go to Steps 14 through 17
to check for vacuum leaks in the vacuum checking
relay and the rotary vacuum valve.
12. To check for proper regulated vacuum output from
the transducer, disconnect the long hose from the
transducer to the vacuum checking relay at the relay
(NOTE: This long hose must be at least 15 inches
tong or the transducer will make a buzzing noise).
Connect the ATC Tester's vacuum gauge directly to
the long hose at the vacuum checking relay.
13. Position the programmer in an upright position so
that the output shaft points straight up. With the
Manual Control knob in the maximum heat position,
"0" volts should be read on the voltmeter and the
vacuum should be 9 to 11 inches. Turning the
Manual Control knob to the MAX. COLD position
should make the vacuum drop to "0" inches and the
voltage should increase 5 volts or more. If these indi-
cations do not occur, the transducer is defective.
After the check is completed, restore hose connec-
tion. Disconnect probe and clip from the program-
mer.
ROTARY VACUUM VALVE AND VACUUM
CHECKING RELAY TEST
14. Connect the tester's vacuum gauge into the vacuum
feed line to the dummy plug on the programmer
rotary vacuum valve. Disconnect the center hose
from the side port of the rotary vacuum valve and
seal off the port by placing your finger over the port.
The tester's vacuum gauge should read 20 inches Hg.
or more. If it does not, either the vacuum checking
relay or the rotary vacuum valve is leaky. If 20 inches
Hg. or more vacuum is read, skip to Step 16 and
restore the hose connection.
Remove all three hoses from the side ports of the
rotary vacuum valve. Remove the short hose from
the transducer and connect it across the two outer
ports on the side of the rotary valve. Place finger over
center side port of the rotary vacuum valve. If the
tester's vacuum gauge now reads 20 inches Hg. or
more, the vacuum checking relay is defecitve. If it
does not, the rotary valve is defective and leaking.
After repair of programmer, restore all hose connec-
tions.
Fig. 18-7 Adjusting Programmer Amplifier Feedback Back
Pot