When the fan is on high it does not run through the blower motor resistor. The low speeds don't work because the blower motor resistor is bad.
yOU NEED A NEW bLOWER MOTER rESISTOR. iT IS LOCATED ON THE BLOWER BOX RIGHT BEHIND THE GLOVE BOX. lOER THE GLOVE BOX BY PRESSING THE TWO SIDES, AND IT ROTATES OUT OF THE WAY. tHE RESISTOR IS HELD IN MY TWO HEC SCREWS. THE PART IS WELL STOCKED AT THE DEALER. iTS ABOUT $18 - $20 AND TAKES 5 MINUTES TO REPLACE Just replaced mine. Chrysler parts dept has a upgraded solid state module part # 68029175AA $23.00
That is a typical sign that the blower resistor has gone faulty
If the blower high setting isn't working on your '97 Dodge Ram Van even after replacing the resistor block, the issue may lie with the blower motor itself or the blower relay. The intermittent operation of the medium setting suggests there could be a loose connection or a failing blower motor. Before replacing the relay, check for any loose wiring or connections and consider testing the blower motor to ensure it's functioning properly. If those components are in good condition, then replacing the blower relay could be a worthwhile step.
The blower setting should depend on your specific needs. A high setting is ideal for quickly drying surfaces or removing debris, while a medium setting is better for quieter operation or delicate tasks. Consider the environment and the material you're working with to choose the appropriate speed.
It could be due to a faulty resistor in the blower motor circuit. The resistor regulates the speed of the blower motor, and if it malfunctions, the high speed setting may not work properly. It would be best to have a mechanic inspect and replace the resistor if necessary.
To adjust the blower speed on your furnace, locate the blower motor and find the speed control switch or dial. Turn the switch or dial to the desired speed setting, typically indicated by numbers or labels such as "low," "medium," or "high." Make sure to consult your furnace's manual for specific instructions on adjusting the blower speed.
Heater blower resistor is what controls the low medium high speeds...
if your blower is working on low and medium speed then it's not a fuse it is the blower switch
If you have 12 volts at the blower, And the blower runs when it is straight wired. The blower switch runs through a resistor that allows the blower to run in low, medium-low, medium-high. Find and check this resistor. Most of the time it is located on the passenger side of the firewall.
usually mounted on or next to blower motor
Most likely the Blower Motor Resistor.
Blower motor speed resistor is partially burned out.