Fan blower motor not working - 1996 Mercedes-Benz C-Class

The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.

HVAC Blower Controls Circuit Description
The blower motor is a variable speed motor. The motor operates at a higher rate when voltage is increased to the maximum level.
The blower motor resistors reduce the voltage supplied from the A/C FAN fuse (LH IP Accessory Wiring Junction Block) when the blower control is set at low and medium speeds (speeds 1-4). The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.

Check the AC fan relay
Symptoms Of A Defective Blower Motor Relay
The blower motor relay's job is to basically bypass the current that passes thru' blower motor resistor and deliver it directly to the blower motor. With the blower motor getting full battery current, it'll run in HI speed.

The most common symptom you'll see, when the blower motor relay fails in your Chevy S10 (GMC S15), is that the blower motor will not run in HI speed (but will run in LO, M1, and M2 speeds).

In some cases, the blower motor will fail and the blower motor will not run in HI but you'll have all of the other speeds working.

https://easyautodiagnostics.com/gm/2.8L/blower-motor-relay-multimeter-test-1

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Try to check the power and ground on the blower fan. If you missing the ground on the blower fan connector than most likely it is the blower fan resistor (controller), it is located under the hood close to back firewall behind left cylinder head.

Do you have power going to the blower motor from the fan relay ?

Hi!!
When the Blower Motor Resistor (controls blower speeds) goes bad, the blower motor works only on HIGH SPEED. REPLACE IT.
BLOWER MOTOR RESISTOR Removal & Installation

• Disconnect negative battery cable.
• Remove right lower instrument panel insulator panel.
• Disconnect blower resistor connector located behind right side of dash.
• Remove blower resistor screws and blower resistor.

To install, reverse removal procedure
Good Luck!! A HELPFUL - 4 THUMBS - rating for this solution would be greatly appreciated. Thank you for using FixYa!!

Hello,
You may want to try your fan on all speeds. If it will work on high, you have a bad resistor for the fan motor. ( high speed doesn't go through the resistor ).
If it doesn't work on any speed, I would check the following;
1. Make sure the fuse isn't blown for the fan blower motor.
2. Check, or have checked the wires between the fan control switch and the fan blower motor.
3. Have the fan control switch checked.
4. Have the fan blower motor checked.

I hope this helps you.

your circuit is simple--I will paste it below. suspect the blower has shorted and caused the switch to burn up. remove the blower and hotwire it to the battery to see if it works. If not, replace the blower. Then run continuity tests on the swoitch and replace switch if bad. If you have questions, please let me know. Here is procedure for taking blower out:

REMOVAL & INSTALLATION With Air Conditioning

1. Disconnect the negative battery cable.
2. Remove the glove compartment door and glove compartment by removing the retaining screws and bolts. Push the sides of the glove box in to free the drawer from dash panel.
3. Loosen the instrument panel at the lower right hand of the glove compartment opening. This is on it necessary if the panel is in the way of the motor housing.
4. Remove the retaining screws securing the ducting around the blower motor.
5. Remove the clip securing the blower motor fan blade to the motor arm. Remove the fan blade from the motor.
6. Remove the blower motor mounting plate from the evaporator case by unscrewing the retaining screws.
7. Rotate the motor until the mounting plate clears the edge of the glove compartment opening and remove the motor.
8. Remove the wire harness from the rear of the motor.
9. Inspect the fan blade for broken edges or cracks. Replace if needed.

To install:

1. Connect the wire harness to the rear of the blower motor.
2. Install the motor into the case and secure with the retaining screws.
3. Position and fasten the fan blade to the blower motor arm. Secure with the clip.
4. Secure the blower motor outer housing to the duct assembly with the retaining screws.
5. Install the instrument panel at the lower right hand side if removed earlier.
6. Install the glove compartment door and glove compartment.
7. Connect the negative battery cable.
8. Run blower motors to make the motor works correctly.
   

Without Air Conditioning

1. Disconnect the negative battery cable.
2. Remove the right ventilator assembly.
3. Remove the hub clamp spring from the blower wheel hub. Pull the blower wheel from the blower motor shaft.
4. Remove the blower motor flange attaching screws located inside the blower housing.
5. Pull the blower motor out from the blower housing (heater case) and disconnect the blower motor wires from the motor.

To install:

1. Connect the wires to the blower motor and position the motor in the blower housing.
2. Install the blower motor attaching screws.
3. Position the blower wheel on the motor shaft and install the hub clamp spring.
4. Install the air inlet duct assembly and the right ventilator assembly.
5. Connect negative battery cab
6. Check the system for proper operation.

Chk for power at the blower motor electrical connector. If no voltage, check the blower motor resistor, its within the blower motor vent (this controls power to the blower motor). Also, in theses vehicles water may have damaged the blower motor itself. Inspect the blower motor for proper function.

Check the blower multispeed control resistor pack is not faulty.
The resistor pack is usually located in the air ducting, in the blower fan airflow.
Basically, +12v power is supplied (via fuse) to the fan speed control switch, which then passes via the selected speed control resistor, to the fan motor. Often a interface relay is used to switch the blower motor high current.

It is the blower motor resistor and is located under the glovebox behind the blower motor.