F 250 4WD Pickup L6-300 4.9L (1982)
Intake Air Temperature Sensor: Testing and Inspection
Component Testing
NOTE: Prior to performing any test on this system, insure that temperature switch is above 65° F.
1.
Disconnect connector from wiring harness.
2.
Connect an ohmmeter or self-powered test light to temperature switch connector terminals.
3.
Cool the switch to below 40° F by spraying with Refrigerant 12.
CAUTION: Do not spray refrigerant with engine running, as any refrigerant drawn into the carburetor and burned in the engine will produce poisonous
phosgene gas. Conduct this procedure in well ventilated area.
4.
When switch is cooled below 40° F.
a.
On type 1 switches, the internal switch contacts should open. The ohmmeter should read maximum resistance or the test light should be off. If
switch does not open below 40° F, replace switch.
b.
On type 2 switches, the internal switch contacts should close. The ohmmeter should read zero resistance and the test light should be on. If test
light does not go on or ohmmeter indicates a resistance of 1 ohm or more, replace switch.
5.
Increase switch temperature to above 70° F by placing palm of hand on metal surface of switch or by starting engine and allowing the exhaust
manifold heat to increase the intake air temperature.
6.
When switch temperature is above 70° F.
a.
On type 1 switches, the internal switch contacts should close. The ohmmeter should read zero resistance and the test light should be on. If test
light does not go on or ohmmeter indicates a resistance of 1 ohm or more, replace switch.
b.
On type 2 switches, the internal switch contacts should open. The ohmmeter should read maximum resistance or the test light should be off. If
switch does not open, replace switch.
c.
If switch is replaced, check operation of new switch before connecting harness connector.
