Blower motor speed problems
12-17-2018, 12:55 PM
#1
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Blower motor speed problems
Hey all, I've been googling my fingers off for weeks trying to figure this out.
AC/Heater blower motor in my 99 is stuck on medium speed.
Here's what I have done:
Took apart control switch and cleaned contacts. All buttons on module work accept the recirculation (light comes on but reading I have done suggests that the button could still be why recirculation doesn't work)
Changed blower motor resistor.
Unplugged and plugged back in all the things. (blower motor, resistor, control switch)
So after all that, it's still stuck. What else could it be? Is there a relay somewhere that needs to be checked? Could the control switch be bad even though it's a simple circuit switch? All other functions are working perfectly, heat, ac compressor, direction control, etc. Thanks for all your smarts and assistance.
AC/Heater blower motor in my 99 is stuck on medium speed.
Here's what I have done:
Took apart control switch and cleaned contacts. All buttons on module work accept the recirculation (light comes on but reading I have done suggests that the button could still be why recirculation doesn't work)
Changed blower motor resistor.
Unplugged and plugged back in all the things. (blower motor, resistor, control switch)
So after all that, it's still stuck. What else could it be? Is there a relay somewhere that needs to be checked? Could the control switch be bad even though it's a simple circuit switch? All other functions are working perfectly, heat, ac compressor, direction control, etc. Thanks for all your smarts and assistance.
Last edited by Lordmonk3y; 12-17-2018 at 06:57 PM. Reason: Forgot to add year
12-17-2018, 06:56 PM
#3
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I also that this. I don't think my resistor is bad though. I even tried one out of my brother's 4th gen max that is working fine and still the same symptoms. My Haynes manual was also no use.
12-18-2018, 04:02 AM
#5
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12-20-2018, 02:53 PM
#6
Do you have the manual controls or the auto climate controls? There is a lot of difference in the fan control.
One commonality is how the fan itself is wired. 12 volts comes from the fuses under the hood to the blower motor. To make the fan spin, the control panel supplies the ground. To give you different speeds, the control panel puts resistance between the fan and ground. Full, direct ground is high speed. No ground is off.
In the manual controls, the switch that you rotate has a separate contact for each of the fan speeds. Speeds 1 through 3 uses the blower motor resistor. Speed 4 is a direct ground to the blower motor, bypassing the resistor. I can visualize the speed switch being messed up and only giving you one speed, but that would be a real stretch of the imagination. Plus, I would think that the # 4 high speed would still work. The switch is replaceable in the control panel.
In the auto climate controls, the fan speed is controlled by a transistor that replaces the blower motor resistor of the manual controls. When you press the fan speed button on the control panel, you are changing the voltage on the control leg (or base) of the transistor.
The blower motor resistor of the manual control system and its counterpart in the auto control system, the fan control amplifier, are not interchangeable. They look identical but won't work in the wrong type of control system.
Without knowing which control panel your car has, I can't get too specific. If you have a voltmeter and can do troubleshooting, I can give you some things to check.
One commonality is how the fan itself is wired. 12 volts comes from the fuses under the hood to the blower motor. To make the fan spin, the control panel supplies the ground. To give you different speeds, the control panel puts resistance between the fan and ground. Full, direct ground is high speed. No ground is off.
In the manual controls, the switch that you rotate has a separate contact for each of the fan speeds. Speeds 1 through 3 uses the blower motor resistor. Speed 4 is a direct ground to the blower motor, bypassing the resistor. I can visualize the speed switch being messed up and only giving you one speed, but that would be a real stretch of the imagination. Plus, I would think that the # 4 high speed would still work. The switch is replaceable in the control panel.
In the auto climate controls, the fan speed is controlled by a transistor that replaces the blower motor resistor of the manual controls. When you press the fan speed button on the control panel, you are changing the voltage on the control leg (or base) of the transistor.
The blower motor resistor of the manual control system and its counterpart in the auto control system, the fan control amplifier, are not interchangeable. They look identical but won't work in the wrong type of control system.
Without knowing which control panel your car has, I can't get too specific. If you have a voltmeter and can do troubleshooting, I can give you some things to check.
12-20-2018, 03:04 PM
#7
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Do you have the manual controls or the auto climate controls? There is a lot of difference in the fan control.
One commonality is how the fan itself is wired. 12 volts comes from the fuses under the hood to the blower motor. To make the fan spin, the control panel supplies the ground. To give you different speeds, the control panel puts resistance between the fan and ground. Full, direct ground is high speed. No ground is off.
In the manual controls, the switch that you rotate has a separate contact for each of the fan speeds. Speeds 1 through 3 uses the blower motor resistor. Speed 4 is a direct ground to the blower motor, bypassing the resistor. I can visualize the speed switch being messed up and only giving you one speed, but that would be a real stretch of the imagination. Plus, I would think that the # 4 high speed would still work. The switch is replaceable in the control panel.
In the auto climate controls, the fan speed is controlled by a transistor that replaces the blower motor resistor of the manual controls. When you press the fan speed button on the control panel, you are changing the voltage on the control leg (or base) of the transistor.
The blower motor resistor of the manual control system and its counterpart in the auto control system, the fan control amplifier, are not interchangeable. They look identical but won't work in the wrong type of control system.
Without knowing which control panel your car has, I can't get too specific. If you have a voltmeter and can do troubleshooting, I can give you some things to check.
One commonality is how the fan itself is wired. 12 volts comes from the fuses under the hood to the blower motor. To make the fan spin, the control panel supplies the ground. To give you different speeds, the control panel puts resistance between the fan and ground. Full, direct ground is high speed. No ground is off.
In the manual controls, the switch that you rotate has a separate contact for each of the fan speeds. Speeds 1 through 3 uses the blower motor resistor. Speed 4 is a direct ground to the blower motor, bypassing the resistor. I can visualize the speed switch being messed up and only giving you one speed, but that would be a real stretch of the imagination. Plus, I would think that the # 4 high speed would still work. The switch is replaceable in the control panel.
In the auto climate controls, the fan speed is controlled by a transistor that replaces the blower motor resistor of the manual controls. When you press the fan speed button on the control panel, you are changing the voltage on the control leg (or base) of the transistor.
The blower motor resistor of the manual control system and its counterpart in the auto control system, the fan control amplifier, are not interchangeable. They look identical but won't work in the wrong type of control system.
Without knowing which control panel your car has, I can't get too specific. If you have a voltmeter and can do troubleshooting, I can give you some things to check.
Last edited by Lordmonk3y; 12-20-2018 at 04:56 PM. Reason: Thought of something else
12-22-2018, 06:45 PM
#9
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It was stuck on high before I took it apart so similar problem I guess. But I'll probably still swap it anyway since I don't know what else there is to replace at this point. I'll update when that's done.
01-01-2019, 05:03 AM
#12
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Okay. So I went and grabbed the control switch out of my brother's 96 and bam. Everything worked perfectly. I don't understand how that simple switch could have possibly gotten stuck on low speed when everything inside it was turning fine, but there you have it. Thanks everyone for the replies.
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