You probably have a faulty blower motor resistor. I believe it is located on bottom of heater box. This I also believe a dealer item.
Something called a blower control module takes the place and is found in the hole where you would find a blower resistor, so there isn't a blower resistor in that vehicle. As far as the blower control module is concerned, the module is serviced as a unit. No part can be fixed or replaced. This is not to be confused with the control head in the dash. The blower control module is held into the heater box with two 8mm screws outside the firewall under the hood, where you would normally find the blower resistor pack.
The blower control module is defective.
either the control head is bad or there is a blower motor resistor that is bad.
Check the A/C fuse, that's what happened on my '85.
It could be the blower itself as well. The first thing I would do is find the wattage of the blower (dc, I assume.) and connect the ground. Is there power to the unit?
If you have checked the blower motor and it does function when power is applied then I would suspect the Blower Motor Resistor Pack is defective. It is also possible the blower motor speed control is bad, but highly unlikely.
Based on the symptoms suggest a progression of failure in the various speeds, I suspect that the blower motor itself is probably OK, and the problem is a failure of the blower "speed control RESISTOR PACK." The speed control resistor pack is usually located on the plenum chamber [the "box" usually located beneath and/or behind the dashboard above the right front passenger's seat floorboard.
That would depend on what you mean by "older". It is either a bad switch, if not a computerized climate control system, or it is a resistor/variable speed blower motor control. If it is the resistor type control, it is usually found mounted on, and going in to the blower motor housing under the dashboard under the glove box. In some vehicles, they can also be located in the engine compartment bolted to the firewall on the passenger side, and going into the blower motor housing from the outside.
blower resistor
You can control the oxygen through aeration
There is a resistor packon the evaporator case and it may be burned out. Have someone look at it.
It could be the motor, switch, relay, corroded or dirty connector, damaged wire or blown fuse.