2000 Maxima SE
Last summer I noticed that when the air conditioning was on with interior air recirculated the fan would cut out running top speed. It would run at the other 4 speeds without a problem so I didn't get too concerned. Now the blower runs at only one speed. I changed the blower resistor without a change. Another development is the blower will run even when it is switched to the off position. Sometimes it will turn off on either the off or position 1 but also may come back on unexpectedly. This sounds like a relay issue (I don't know where to find it) and certainly the motor has seen 17 years of use. I would like to know what to make of this.

 

I literally just had this same problem and just posted about the resolution yesterday. I had the same issue.

Replace the blower motor speed switch.

I got mine on ebay:

http://www.ebay.com/itm/HVAC-Blower-...72.m2749.l2649

Look for my post a few down from this one.

 

How involved is it to get to to replace the blower motor speed switch?

 

Cliff notes version -

remove air vents above radio.
remove ash tray
trim plate around shift lever
remove radio pod with radio & heater controls
remove heater controls
remove switch.

 

That pretty much sums it up. Give yourself an hour or so to do it.