I think the problem is with the heater motor resistor pack which you will find located near the fan motor. Open the hood and look to the left side corner of the fire wall. I have a 95 Astro and my resistor pack is located on top of the heater blower housing. I have changed many of these resisters on different makes and have found them to have their resistors rusted. The resistors are made of wire and they rtust and burn out. Find the small plug that goes to the resistors and you will find a a plate which has two screws, one on each end of the resistor pack. Remove the two screws and pull out the resistor pack. You can either get a used one from the junk yard or purchase one from a Chevy dealer. The resistor is used to control the different fan speeds and is located in the the blower housing so that the fan helps cool the resistors when the fan is running.
Check connections at the blower motor, blower motor resistor and at the switch. You may find a melted connection.
sounds like a bad blower motor resistor and or plug
What can happen when a blower motor resistor goes bad is that the motor will run and then suddenly stop running on a regular basis. Sometimes the blower fan will not turn on and cause the motor to overheat.
Sounds like the wire that goes to the blower that is behind the glove box which you would have to remove then pull the wire off and push back on, that's usually the problem.
The blower motors only work with the engine running. If the blower motor has three wires on the electrical plug, then the blower motor module is built into the unit & it's very expensive. Sometimes, you can tap on the motor with a hammer & it may work or slowly turn. If this is the case, replace the blower motor.
There could be two separate problems. Check the blower motor resister, and the ABS sensors for problems that could cause this.
Check/ replace the blower resistor. Located in the duct work under the hood. Follow the wires from the blower motor to a plug on the duct work. This is the resistor
If there is an issue with your Ford Focus heater that blows intermittently it is a sign that the blower needs to be replaced or cleaned. A certified mechanic can do a diagnostic check to verify and make the necessary repairs.
Loose connection or blower motor? Bad blower motor? Loose fuse? Bad fan switch?
If the blower motor randomly and intermittenly quits and does not work, chances are good the blower motor itself is faulty, if the blower motor does not work on all fan speeds from low through high, it most likely needs a blower motor resistor.
Probably the blower motor, wiring to it or control switch
If the heater blower has humming noise when motor is running, first check its capacitor. If the capacitor is fine, then the motor is the problem and may need to be replaced.