98 mercedes e 320 heater blower does not work

fan motor relay is for fan speeds
heater and AC

blower motor has a resistor
did the motor bench test ok
if fan motorand resistor are ok
i suspect
a faulty on /off switch in the dash panel

i think that system has electronic directional flap actuators not vacuum ..if vacuum might be a leak ..

most likely is the 'resistor' that controls the fan speed. try 'jumping it' with a 10 gauge wire--blower should run on max speed.

all cars and truck they all have a resistor for the fan speeds it should down by the heater fan , now on the dash controller do you have power to it , some cars have two fuses ,one for fan and one for the controller

all speeds go through the resistor except high that is why it will work on high you are bypassing the resistor if you are sure the resistor is good it has to be the blower spped switch on the dash

Check fuses 52 15A and 51 15A in the underhood fuse box. Check the Blower motor relay behind the right side of dash. Check the fan control amplifier (controls fan speed) behind right side of dash. Sound more like a blown fuse or bad blower motor relay

I wish I could help with the exact location but most are in the fuse panel under the hood, but since you said you charged the ac, im wondering if you overcharged the the ac, because there is a high pressure sensor that will shut off the operation of your heater and ac control unit inside on the dash when you overcharge with freeon.

check the blower fuse? check for voltage at the switch (requires removing heater / ac controls from dash on most vehicles.)

replace the complete heater control unit was my only fix! over $700 in Cnada for control.

check the following. #1, it could be the flap soliniods. This is located behind the dash on the heater box. This operates the flpas to regulate hot and cold air. The clicking sound could meen that it's trying to operate but can not due to a dying motor. You need to check which one is faulty. from memory there is about 4 or 5. #2. Behind the a/c fan speed control there is small plug. Sometimes this can be left unplugged if someone has worked on the car. e.g installing a new Radio/cd player etc.
good luck.