DESCRIPTION
All RWD passenger cars are equipped with an electric assist choke to help reduce emissions during engine warm-up. A dual-stage control unit assists engine warm-up in summer and winter operation by allowing more current to reach the choke heating element when temperature is more than 80°F (27°C).
OPERATION
Note. Information on 5.2L 4-Bbl. models is not available.
On 2-Bbl. models, electrical current is supplied from the oil pressure switch. A minimum of 4 psi (.28 kg/cm 2 ) oil pressure is required to close contacts in the oil pressure switch and provide electrical current to choke control switch. The control then routes power to the choke heating element.
The dual-stage control unit will shorten choke duration when temperatures are more than 80°F (27°C), and it will stabilize choke operation in the winter (summer electric assist is hotter than winter heat level). Engine temperature controls a switch inside the dual-stage control. At temperatures less than 55°F (13°C), electric power is reduced by a resistor. When temperatures are more than 80°F (27°C), the resistor is by-passed and full heat is supplied. This action shortens choke duration.
Engines started in winter conditions will experience 2 levels of choke heat. A low heat level is used during engine warm-up and high heat level is used after engine warm-up.
Scheme 271
FUNCTIONAL CHECK
- Check test light by connecting between battery terminals of car battery. Observe intensity of light. Before starting engine, remove ignition harness electrical connector from control switch. (Scheme 271)
- Connect test light to choke terminal of control switch and ground. Start engine and allow to reach normal operating temperature. Apply 12 volts to ignition harness terminal of control switch. If test light does not light or does not have same intensity as in step 1), control switch is defective and should be replaced.
CHOKE HEATING ELEMENT
- Disconnect battery voltage (B+) wire from the control switch. Connect an ohmmeter lead to choke housing or choke retainer screw. Touch other lead to a bare portion of choke wire connector at switch (not the battery voltage terminal).
- Resistance of 4-12 ohms indicates the heating element is electrically functional. Replace choke assembly if ohmmeter readings indicate an open or short circuit.