My heating/airconditioner blower only works on high speed, the other positions do nothing.

means heat on high blower fails too, not told
the blower must not fail on all speed settings
does it or not?

they both share the blower fan
the fuse is marked blower.
does the blower work on high only or dead on all speeds
this is the first tests.
ask for more.

Blower resistor must be bad ,think It's under the pass dash

replace your blower motor resistor. this controls the speed of the blower motor.

The resistors provide resistance in the circuit, dropping voltage to the blower motor to slow the motor speed down. On high, the blower receives full voltage through the blower relay.

If you had High but no other speeds, then the resistor pack is usually the culprit. If you have all other speeds but high, the most common problem is going to be the blower motor itself, relay, or the switch panel.

You can check this by turning the fan speed to "high", unplug the blower motor, and check to see that you have roughly at least 12v at the plug. If you have 12v, that means the switch panel is activating the relay and the relay is working. Over time, heat kills the magnetic properties of the magnets inside an electrical motor. Without enough magnetic energy, you may not get enough opposing force to spin the rotor full speed when the windings energize, but still enough to spin at lower speeds.

Another thing you can check is the connector at the blower motor and the switch panel. Sometimes these will heat up, start to deform, and cause a bad connection. The bad connection may be able to handle the lower current draw on low speeds, but the higher resistance from the bad connection won't be able to handle the higher current while in the full speed position.

Hope this helps, keep me posted. be glad to help you get your heater working again soon.

Well it sounds like the blower motor relay is out you might also need a blower motor if it is using to much juice on high speed then the blower motor is probabley about to go out and with the noise you are describing it sounds like a bearing in the blower motor is about to go out so probabley should change the blower motor and the blower motor relay.

There is a HVAC relay and FUSE in the under hood fuse box, have you check both of these? If the blower works on any speed, the blower is good. You say it blows on lowest speed? The blower speed resistor is mounted on the blower housing. The HIGH SPEED BLOWER RELAY is mounted on the blower motor. You may have multiple problems but check fuses first, if all is OK, then a qualified repair shop will need to check further. You do NOT need the whole A/C system replaced. If it does blow cold, thats good, you just need the blower working.

If the blower motor only works on the high speed it most likely needs to the blower motor resistors replaced. Sometimes when replacing the resistors the dealer recommends that the blower motor be replaced in conjunction. It's believed the blower motor burns out the resistors. The resistor pack is either in the engine bay mounted on the heater box or under the passenger side of the dash board.

Change blower resistor.

yes, all blower motors have them to control their speed, High, medium, low.. etc. I earn nothing by helping you, but my rating, a fixya rating and I will walk you through this