Questionheater will not blow warm air
AnswerHi Linda,
You didn't mention which type of heater/ac control unit you have:automatic with digital readout or conventional. Both types have a self diagnostic capability you can avail yourself of. Here is the one for the conventional unit. If you have the ATC unit let me know and I'll give you that procedure:
There is a rear window defogger that is initiated by a push button with an LED light. That light is the readout, by its blinking. To begin the diagnostic mode, run the vehicle at idle with the controls set as follows: the blower speed knob should be on any position other than OFF, the temperature knob should be set in full COOL, and the mode knob should be set on Defrost mode.
To enter the diagnostic mode, press the defogger switch in for five seconds, until it begins to blink, then release it. It will continue to blink for about 30 seconds while it calibrates. If it goes out, the calibration is OK and you can skip 3 paragraphs to "Position...mix mode" below.
If the light stayed on, switch the mode knob to the MIX (defroster-floor) position. If the light stays on there is a problem with the control head unit.
Switch the mode knob to the FLOOR position, if the light stays on, it indicates a problem in the blend door or the blend door actuator wiring.
Move the knob to the Bi-level (panel-floor) position where a continuous light indicates a problem with mode actuator or circuit.
Position the knob in the MIX mode. The LED light should now flash twice then pause, and continue a two-flash sequence, indicating that the MIX mode is OK.
In the FLOOR mode the light should flash three times, meaning that the FLOOR mode is OK.
In the Bi-Level Mode, a four-flash sequence indicates that mode is OK.
In the PANEL mode the light should flash 5 times to indicate no problems there, and in the recirc-panel mode 6 times and seven times in the recirc Bi-level mode.
The temperature control can be checked by switching the mode knob to Defrost and rotating the temperture knob. If the temperature contol is OK, the light will flash faster the more you turn the temperature knob up, until the light goes out at the hottest setting.
Switch the knob between Panel and Recirc-Panel and watch the recirc door (unit under the dash). Proper operation means that circuit and components are OK.
To get out of the self-diagnostic mode, turn off the blower or push the air conditioning button once.
Let me know what you learn or if you have the ATC unit. It might be that the heater core is clogged so that the hot water is not circulating through it. You could tell that by touching the two hoses that go through the firewall and to the heater. After you have been running the car for a while feel those two hoses. If one is clearly cold while the other is hot then that is your problem.
Roland
