Recently, when I turn on the heater or A/C in my car, it will only work when I switch it onto the highest setting. None of the lower settings work. Also, when I turn on the windshield wipers sometimes nothing will happen or sometimes when they are on, they stop temporarily. They don’t seem to be at the right pace as the speed setting. The windshield wiper situation has been going on for over a year. Does anyone have an idea as to what might cause these problems?
The fan issue is likely the fan resistor - very commonly the case with hi-speed operation only. Note that a bad resistor is often the result of a fan on its way out as well. There is also some possibility that it is the fan switch itself. These things can be tested with multimeter.
The wiper things is probably the wiper switch. Those can be tested, but at the car’s age I’d be tempted to just replace it.
The fan problem can be caused from either a defective fan resistor module as mentioned or from a defective high speed blower motor relay. This relay switches the voltage to either the fan resistor module for all the low speeds or switches the voltage directly to the blower motor for the high speed.
I’ve seen people replace these expensive fan resistor modules thinking that was the problem, when in fact an inexpensive high speed blower motor relay was the problem.
Tester