1981-87 CHEV PICK-UP - Vintage Air

TROUBLE SHOOTING INFORMATION CONT.4. SYSTEM WILL NOT TURN ON ORRUNS INTERMITTENLYWORKS WHN ENGINE IS NOTRUNNING, SHUTS OFF WHENENGINE IS STARTED.(TYPICALLY EARLY GEN 4, BUTPOSSIBLE ON ALL VERSIONS)WILL NOT TURN ON UNDER ANYCONDITIONSNO MODE CHANGE AT ALLPARTIAL FUNCTION OF MODEDOORS5. LOSS OF MODE DOORFUNCTIONBATTERY VOLTAGE IS AT LEAST12V.BATTERY VOLTAGES IS LESSTHAN 12VNOISE INTERFERENCE FROM EITHER IGNITION ORALTERNATORINSTALL CAPACITORS ON IGN. COIL, AND ALTERNATOR.ENSURE GOOD GROUND AT ALL POINTS. RELOCATE COILAND ASSOCIATED WIRING AWAY FROM ECU AND ECUWIRING. CHECK FOR BURNED OR LOOSE PLUG WIRES.IGNITION NOISE (RADIATED OR CONDUCTED)WILL CAUSE THE SYSTEM TO SHUT DOWN DUETO HIGH VOLTAGE SPIKES. IF THIS IS SUSPECTED,CHECK WITH A QUALITY OSCILISCOPE. SPIKESGREATER THAN 16V WILL SHUT DOWN ECU.INSTALL A RADIO CAPACITOR AT THE POSITIVEPOST OF THE IGNITION COIL (SEE RADIOCAPACITOR INSTALLATION BULLETEN). A FAULTYALTERNATOR OR WORN OUT BATTERY CAN ALSORESULT IN THIS CONDITION FOR ALTERNATORREGULATOR TO FUNCTION PROPERLY.VERIFY CONNECTIONS ON POWER LEAD, IGNITIONLEAD, AND BOTH WHITE GROUND WIRESVERIFY BATTERY VOLTAGE IS GREATER THAN 10VOLTS AND LESS THAN 16.CHECK FOR POSITIVE POWER AT HEATER VALVE GREENWIRE. AND BLOWER RED WIRE. CHECK FOR GROUNDON CONTROL HEAD WHITE WIREVERIFY PROPER METER FUNCTION BY CHECKING AKNOWN GOOD BATTERYS VOLTAGE.CHECK FOR DAMAGED MODE SWITCH OR POT ANDASSOCIATED WIRINGCHECK FOR OBSTRUCTED OR BINDING MODEDOORSCHECK FOR DAMAGED STEPPER MOTOR ORWIRINGTYPICALLY CAUSED BY EVAPORATOR HOUSINGINSTALLED IN A BLIND IN THE VEHICLE. BE SUREALL MOUNTING LOCATIONS LINE UP AND DON’THAVE TO BE FORCED INTO POSITION.CHECK FOR AT LEAST 12V BETWEEN GREENHEATER VALVE WIRE AND CHASSIS GROUND.CHECK FOR FAULTY BATTERY OR ALTERNATORINSURE ALL SYSTEM GROUNDS AND POWERCONNECTION ARE CLEAN AND TIGHT.CHARGE BATTERYSYSTEM SHUTS OFF BLOWER AT 10V. POORCONNECTIONS OR WEAK BATTERY CAN CAUSESHUT DOWN AT UP TO 11VCHECK FOR DAMAGED SWITCH OR POT ANDASSOCIATED WIRINGREPAIR OR REPLACETHIS IS AN INDICATOR THAT THE SYSTEM HASBEEN RESET. BE SURE THE RED POWER WIRE IS ONTHE BATTERY POST AND NOT ON A SWITCHEDSOURCE. ALSO, IF THE SYSTEM IS PULLED BELOW7V EVEN FOR A SPLIT SECOND, THE SYSTEM WILLRESET.RUN RED POWER WIRE DIRECTLY TO BATTERY6. BLOWER TURNS ON AND OFFRAPIDLY901182 REV A 6/13/11, INST 81-87 CHEV P-UP wo AC EVAP KIT PG 24 OF 277. ERATIC FUNCTIONS OFBLOWER, MODE , TEMP, ETC.8. WHEN THE IGNITION IS TURNEDON, THE BLOWER MOMENTARILYCOMES ON, THEN SHUTS OFF.THIS IS WITH THE BLOWERSWITCH IN THE OFF POSITION24