Testing Sensor Circuit For An Open

Use Tester voltmeter probe, position voltage knob in the probe position, attach Tester ground clip to car and disconnect power plug from amplifier.
Place ignition switch in the accessory position, then test for battery voltage at both terminals on all three connectors. Obtaining a voltage reading at both terminals indicates a good sensor or potentiometer. Obtaining a voltage reading at one terminal only indicates an open circuit in the sensor or potentiometer. Replace sensor or potentiometer.
No voltage at either terminal on a sensor or potentiometer indicates the open circuit is at one of the other sensors or the battery feed wire to the sensor circuit is open.

Temp.	Outside Sensor Ohms	Sensor on Control Ohms
60°	44	95
65°	41	86
70°	38	76
75°	36	68
80°	34	60
85°	32	55
90°	30	50
95°	27	45
100°	23	40
Sensor Resistance (except node) (Plus or minus 5%)

Temp.	Duct Sensor Ohms	Ambient Sensor Ohms	In-Car Sensor Ohms
60°	58	40	95
65°	56	37	86
70°	53	35	76
75°	50	34	68
80°	47 1/2	32	60
85°	45	30	55
90°	42 1/2	28	50
95°	39	27	45
100°	37 1/2	25	40
Sensor Resistance (Toronado) (Plus or minus 5%)