AC/Heat problem
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Joined: Aug 2006
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AC/Heat problem
I have a 99 expedition and am having a problem with the dash ac/heater control. The panel lights up and everything appears and works normal except the fan does not work. When I checked the ac the clutch is turning and all fuses appear normal. The overhead console seems to be working fine but the air blowing out is not really cool. This has happened once before but on the next start everything worked fine and has continued to work until now. Anyone have this problem before or know what the problem might be and where to look. Thanks
Hotshot
Joined: Jan 2004
Posts: 19,765
Likes: 1,082
From: St Louis
If you have "NO" airflow from the vents, you've completely lost ALL blower function.
If you have "SOME" airflow, then it's a different issue.
For "NO" airflow:
Check for power on both leads of the blower motor. If battery power is on one terminal but the other side reads zero regardless of speed switch position, then the motor is probably bad.
If both leads read battery power, there is an open circuit between the motor and ground.
If both leads show zero voltage, then either there is an open 40a fuse (F105 in the BJB), faulty blower relay, or other open circuit.
For "SOME" airflow:
Measure the voltages at the two motor leads. One should be battery voltage. The other will measure a lower voltage depending on the position of the speed switch. On HIGH, the low side should be zero. For each higher speed setting, the low side lead will measure a higher voltage.
Typically, a resistor pack failure cause only HIGH speed to operate. All other settings are dead.
A switch failure will cause one or more speed settings to have no effect, but the blower will always operated on LOW at least.
Do some checks and get back to us.
Steve
If you have "SOME" airflow, then it's a different issue.
For "NO" airflow:
Check for power on both leads of the blower motor. If battery power is on one terminal but the other side reads zero regardless of speed switch position, then the motor is probably bad.
If both leads read battery power, there is an open circuit between the motor and ground.
If both leads show zero voltage, then either there is an open 40a fuse (F105 in the BJB), faulty blower relay, or other open circuit.
For "SOME" airflow:
Measure the voltages at the two motor leads. One should be battery voltage. The other will measure a lower voltage depending on the position of the speed switch. On HIGH, the low side should be zero. For each higher speed setting, the low side lead will measure a higher voltage.
Typically, a resistor pack failure cause only HIGH speed to operate. All other settings are dead.
A switch failure will cause one or more speed settings to have no effect, but the blower will always operated on LOW at least.
Do some checks and get back to us.
Steve
Freshman User
Joined: Jul 2004
Posts: 49
Likes: 0
From: Rochester, MN
Is there a thread with a picture of where the resistor is? I am pretty sure that is my problem, I only have low and high speed for the fan.
also my HVAC panel has no lights that work. Could that be the resistor too?
also my HVAC panel has no lights that work. Could that be the resistor too?
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