Nissan-Heater/ac Fan

I am not sure what the problem is on this 99’ Nissan Altma fan. The fan works on heat and a/c only when it’s switched on max. but not on low one, two, and three. How should I takle this issue.


I’ve had a similar issue at least 3 times with my 2000 Cavalier. It was the blower motor relay - goes bad on my car about every 30-40K.

The fan speed is controlled by switching resistors into the fan circuit. The resistors are bad so the only speed that works is max. (no resistor used)

the resistor assembly is typically located in the ductwork.

There may also be an underlying reason why the resistor is bad, and this applies to the poster who has repeated resistor failures.

An aged car with high mileage means the blower motor has seen a lot of use. A worn and dragging blower motor will consume more current than a new motor.
More current means more heat and since the resistor is near glowing red anyway it will burn out faster.

It would be the same principle as having a compressor going out in an household central AC unit. Dragging compressor uses more current which in turn pops the circuit breaker, or eventually sets the house on fire if the breaker is constantly reset.

Correction to my 9/12 post - the subsequent 2 posters are right, of course…it’s the resistor (not relay) that keeps going bad on my chevy.

How would I fix it? Can this be a job I do or does it have to be done with a shop.