Re: Blower motor fan only goes on when switch is on...
I have the same problem. I took out the heater/AC control unit and noted that all the controls are mechanical, i.e. linkages can break, gears grind down etc. My gear for blower positioning is totally gone, so its stuck on feet. My blower setting can only go from nothing (vent) to ultra high. The easiest fix, which I am currently looking into is to replace the whole unit from a car from the junkyard. I feel that trying to get the manufacturer to send me a gear would be a bit time consuming. Check around to your local junkyards. It will take a couple minutes and a screw driver to install. Hope this helps.
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On a Chrysler product, the blower switch and resistor provides the ground circuit for the blower motor. The highest speed circuit which is dark blue and gray goes thru the resistor directly to the fan switch. The other speeds go thru the resistor to slow down the motor. One wire from the switch should be a direct to ground, the other 5 wires should have voltage coming from the blower motor thru the resistor.
The blower motor fan is controlled by the blower motor resistor.Its the resistor which controls the fan on respective speed which you select.But if the resistor goes faulty,then it will not be able to set the required speed which you set for fan,so it works on high speed only.
In this case you will have to replace the blower motor resistor.
Check fog for the location of blower motor resistor location:--- see part number 8 in the diagram below.
The blower motor resistor is located next to blower motor under the dash.Its fitted with 2 screws and a wiring connector.You have to remove the screws and wiring connector and take the resistor out and place the new resistor in same position and connect the connector as well as screws.
this should help.Thanks.Helpmech.
Different speed settings on the blower motor is achieced by using resistors mounted on a circuit board usually fitted in the airstream of the system. For the highest speed setting the blower motor is connected directly to the battery (by way of the switch of course). Lower fan speeds are achieved by lowering the voltage(using a resistor between the battery and fan). These resistors get pretty hot and sometimes burn through thereby not letting power through to the fan motor. The first place to start looking would be under the passenger side dash. Look for a connector plug in the ducting close to the fan motor with at least 3 wires connected to it. On the Silverado for instance it is accessed from below the glovebox, there is a large plastic cover that needs to be removed first. It is fitted to the fan housing.
replace the blower motor resistor. It controls the fan speeds. It defaults to high speed only when it fails.
How to replace the blower motor resistor block:
Caution: Stay clear of the blower motor and resistor block (Hot). Do not operate the blower motor with the resistor block removed.
1. Disconnect and isolate the battery negative cable. 2. Remove the glove box from the instrument panel. 3. Pull out the lock on the blower motor resistor wire harness connector to unlock the connector latch. 4. Depress the latch on the blower motor resistor wire harness connector and disconnect the connector from the resistor. 5. Remove the two screws that secure the blower motor resistor block to the HVAC housing. 6. Remove the resistor block from the HVAC housing.
Installation: 1. Position the blower motor resistor block into the HVAC housing. 2. Install the two screws that secure the resistor block to the HVAC housing. Tighten the screws to 2.2 Nm (20 in. lbs.) 3. Connect the wire harness connector to the resistor block. 4. Push in the lock on the blower motor resistor wire harness connecgtor to lock the connector latch. 5. Install the glove box. 6. Reconnect the battery negative cable. 7. Have a nice day!
Usually when the blower fan only operates on hi speed, its because of a failed blower motor resistor. You still have hi speed because on hi, the power going to the blower motor goes directly to it, as opposed to the lower speeds, when the power is routed through the resistor, thus lowering the voltage, which in turn lowers the speed of the fan. The resistor is usually located near the blower motor itself, under the hood back near the firewall.
The resistors are in circuit only on the lower fan speed settings.
On the highest speed setting, power is switched directly to the fan motor.
Check fan power supply fuses,
Check power is available to the fan when high speed selected.
If all above OK, apply power directly to the motor to verify fan motor runs- if it doesn't the motor may need replacement/repair.
A/C fans only really have (2) speeds. (0)Off... and (4)On. Settings 1,2,and 3 are governed by a series of two resistors which in combinations (one, the other...then both) can limit the speed of the fan. When the circuit with these resistors goes bad, the middle speeds of your fan will cease to work. Since the highest setting is unresisted it will never stop working... unless your fan fails.
The solution is economical as these are simple inexpensive parts. For simplicity, the panel with the resistors is typically located in the dash, right behind the speed selector knob. It may be an integral component with the knob assembly depending on your manufacturer. Replace the assembly, or simply the resistors if you are lucky. On the bright note, it doesn't sound like you need to mess with your blower moter... its fine.
I had the same exact symptom (02 Prizm LSI)..Order yourself a Blower Motor Resistor (I clicked on it---scroll up on this same screen that you are reading--- AC Delco part, $25.79). When the part arrives, look at it, and then look behind and to the left of your glove box door, YOU WILL SEE IT RIGHT AWAY. 2 screws, takes about 10 minutes to change. Its been nice to get all 4 speeds back! Good luck.
On your Vehicle the problem for the FAN speed is NOT the FAN switch.
99.9 % of this problem on cars is the BLOWER MOTOR RESISTOR.
The blower motor resistor give the speed to the Fan.
But on High speed the switch make a By pass of the switch using a Relay for the high speed.
The Blower motor resistor, is located Beside of the Blower motor On the passanger compartment.
If you replace the blower motor resistor you have 99.9% of this will solve your problem.
I'm a Mechanic.
I hope this help on your problem.
Thank you for use fixya...