K 1500 Truck 4WD V6-262 4.3L (1991)
CAUTION: Do not use a meter with an impedance of less than 10 Meg ohms.
Insert the positive voltmeter probe into terminal H (circuit 903) and the negative probe into terminal 4 (circuit 904). Press mode button and voltage
should read 6-8 volts. If no voltage - replace control. If 6-8 volts - check Mode Feedback Potentiometer by inserting the positive voltmeter probe into
terminal D (circuit 362) and the negative probe into terminal 11 (circuit 361). Test the voltages in all three positions and compare them to the values
below.
Mode Door Position .............................................................................................................................................................................. Correct Feedback
Voltage ............................................................................................................................................................................................................ (+/- 0.08V)
Full Vent (A/C) ....................................................................................................................................................................................................... 0.20V
Full Lower (Heater) ................................................................................................................................................................................................. 2.50V
Full Defrost ............................................................................................................................................................................................................. 4.77V
If voltages are different than those shown above - remove the actuator. With the actuator removed, move the mode door lever to make sure the mode