Jeep 1987 Wrangler Workshop Manual page 1786

DESCRIPTION
Both the manifold heater and the electric choke are
related to cold weather driveability. The manifold heater
aids fuel vaporization by warming the incoming cool air.
The electric choke is needed to op>en.the.choke plate as the
engine warms and no longer requires the rich mixtures
required for cold start-up and driveability.
The electric choke and the relay coil receive battery volt-
age from ignition switch terminal 13. The higher current
draw manifold heater receives battery voltage from fuse
link C which is linked to the heater through the relay
contacts.
3. MANIFOLD HEATER: Separate C195 from manifold heater; turn ignition
switch to OFF
The electric choke switch, which is wired in series with
the choke heater and manifold heater relay coil, prevents
operation of these circuits unless the engine is running.
While the electric choke operates whenever the engine is
running, the manifold heater will operate only until engine
coolant temperature reaches 160°F (70 °C). At this tem-
perature, the heater switch contacts open the relay coil
ground circuit and the relay contacts open.
TROUBLESHOOTING
1. MANIFOLD HEATER RELAY: Cold engine; connect jumper wire across
electric choke switch; separate C126 from manifold heater relay; turn
ignition switch to RUN for voltage tests; turn ignition switch to OFF for
resistance tests
TEST OK
NOT O K
C126 cavity 5 Battery voltage Repair open from ignition switch
C126 cavity 4 Battery voltage Repair open from fuse link C
C126 cavity 2 to clean chassis
ground
Zero ohms Repair open between C126 and manifold heater switch
or replace manifold heater switch
C126 cavity 1 to C195 Zero ohms Repair open between C126 and C195
T E S T
O K NOT O K
Measure resistance between
heater terminal and a clean
chassis ground
0.7 ± 0.2 ohms Replace manifold heater
4. BI-METALLIC ELECTRIC CHOKE: Separate C193 from bi-metallic electric
choke; connect jumper wire across electric choke switch; turn ignition switch
to RUN for voltage tests; turn ignition switch to OFF for resistance tests
TEST
O K
NOT OK
C193 Battery voltage
Repair open from ignition switch
Measure resistance between
heater terminal and a clean
chassis ground
4 ± 0.5 ohms Replace bi-metallic electric choke
5. ELECTRIC CHOKE SWITCH: Disconnect C122; start engine
NOTE: Be certain engine oil pressure rises above 4 psi
T E S T O K
NOT OK
Measure resistance across
electric choke switch terminals
Zero ohms Replace electric choke switch
2. MANIFOLD HEATER RELAY: Cold engine; leave jumper wire across
electric choke switch; reconnect C126 to manifold heater relay;
separate C195 from manifold heater; turn ignition switch to RUN
T E S T O K
NOT OK
C195 Battery voltage Replace manifold heater relay
18 Carburetor Circuits
18 Carburetor Circuits