When I use the heater, the blower fan makes a chirping noise in positions 1 and 2. 3 and 4 are fine. What is the cause and fix for this?

 

Same thing happened to my heater fan. I was still under warranty at the time, so I took it to the dealer and they replaced it. As usual, the service managers at the dealer were idiots and all they could do to explain the problem was to say it was "an internal failure in the blower motor."

If you are out of warranty, it will cost around $250 to replace it. The part is $190 from Nissan, and it takes around an hour to install it ($60 labor). In that case, I would just wait until the unit breaks then replace it.

 

Idea #1) A cracked A/C housing.
The blower motor is mounted to a plastic duct or housing. There may be a small crack in that housing which squeaks under certain conditions. Test for this possibilty by running the blower on speed 1 or 2 and when the squeak is heard, use your hand or foot to press gently on the blower motor. If the sound immediately vanishes that is a sign of a crack. The remedy is to find the crack and goop it up real well with a sealer of some kind. Products such as silicon rubber RTV or Welder or Shoe Goo would do the job.

Idea #2) The blower motor needs lubrication.
Remove the blower motor so you can bench test it. Use a pair of fused test leads to supply 12 volts directly from the battery. If the blower motor shrieks, it probably has dry bearings. Being a thrifty sort, I would always try to rehabilitate the old motor rather than install a replacement. Blower motors typically don't have ball bearings; the armature shaft spins in sintered bronze bearings. You may be able to lubricate them and give that blower motor a new lease on life. Use a light lubricant such as 3-in-1 electric motor oil.

 

I have the same squeeking on my '99 Max, so I figure its a fairly common problem. I'm still under warranty so I figure I'll get it checked (nothing better than new parts), but if they won't replace it I'll follow Daniel's advice.
Thanks Daniel
-hype

 

This is a common problem (also with my 98) if you go the the natl highway and trans board web page they list this as a common problem

 

Thanks for the suggestions!