The A/C in my 2001 Nissan Pathfinder (~153,000 miles) only works on high as of this afternoon’s commute. This seems like a common problem on older cars - what’s the typical cause? Googling just gives me all sorts of answers and I would like to have some background before calling our mechanic. I appreciate any advice!
The fan motor gets slowed down by a set of resistors which include a thermal braker. This breaker is probably blown and you need a new resistor. The high speed is the 12v direct to the motor.
Next to wonder what caused an overload enough to blow the breaker ?
A fan motor with wear and drag can cause the circuit to pull additional amps, enough to burn out the resistor pack. You may want to consider replacing the blower motor, too.
Agreed that the problem is not with the air conditioning system itself but just the blower fan, and most likely only the resistor that controls its speed. You may be able to replace the resistor unit yourself if you can locate it. Otherwise, have a mechanic do it and don’t let him talk you into additional and more expensive repairs.
The A/C in my 2001 Nissan Pathfinder only works on high
Most likely the the slow/medium speeds are controlled by resistors. The resistors go out one by one. It seems most people wait until all except high works.
If you can solder and don’t mind doing it yourself, likely you can fix it for almost nothing. Just get the same rated resistors to replace the ones that are bad.
Most any independent mechanic can do the work.
I just fixed this in my wife’s 2002 Pathfinder, which is slightly different, but works on the same principal. The part is relatively inexpensive (around $35) and fits into the air ducts behind the glove compartment, which you’ll have to remove. The unit consists of the body and a heat-sink with screw holes for mounting. (the body fits on the passenger side, the heat sink goes into the air flow inside the duct) The resistor, which turns excess voltage into heat, is cooled by the air flowing past. If the cabin filter is clogged up, airflow slows and less heat is dissipated, potentially speeding up the demise of the electronics. So, it’s worth replacing the cabin filter at the same time. Good luck!
Thank you for all your help!