2003 Pathfinder LE 'knocking' noise related to defroster

[kikafer]

Hey guys,

I'm new to Nissan ownership and hoping to find someone who can shed some light on an issue I'm having. I have an '03 Pathfinder LE. I am getting a rather loud repetitive knocking or banging noise whenever the windshield defroster comes on. By repetitive I mean 1 'knock' every half second roughly, continuously. hearing it makes me picture a malfunctioning solenoid. With the defroster on, hot air is indeed being blown through the defroster, but after ~ 2 seconds of being on, I keep getting the knocking noise, seemingly coming from directly behind the radio/climate control cluster.

I am neither a mechanic nor an internet search expert, so I keep getting the same results in trying to research the problem. Everything I find points to the blend door actuator, however, as I said, there is indeed hot air coming our of the defroster when activated. Literally everything about the climate control system seems to be operating as its supposed to, to my untrained eye, except for this knocking noise.

I believe it is directly related to the defroster and not the climate control system in general due to the noise only happening when the in full defrost mode, or in the mode split between defrost and blowing at your feet. The other modes, that do not include defrost, have no issues.

Any info or advice would be greatly appreciated!

[Hawairish]

Actually, it probably is the climate control system...indirectly. I'm certain you've got the automatic climate system, and it's attempting to cycle the blend doors, but they're not able to get into either of the defrost positions.

This could mean two things:
1. The door positions are out of sync
2. Something plastic is cracked related to the blend doors.

That clicking noise may very well be the blend door motors spinning against a plastic gear tooth...perhaps a tooth has chipped, or the some plastic nearby has cracked allowing the teeth to slip (click click click).

Take a look at the Factory Service Manual and try using the diagnostic mode of the climate control system:
http://www.nicoclub.com/FSM/Pathfinder/ ... der/ha.pdf

The diagnostic mode will tell you an error code and how to remedy it.

[kikafer]

I'm certain you've got the automatic climate system

I do indeed have the automatic climate system.

1. The door positions are out of sync

If this were the case, would the motor continue to 'spin' and try repositioning the door? Would there be a fix that doesn't include dismantling the entire dash?

That clicking noise may very well be the blend door motors spinning against a plastic gear tooth...perhaps a tooth has chipped, or the some plastic nearby has cracked allowing the teeth to slip (click click click).

This hadn't occurred to me. I like the train of thought, however, I assume that once the blend door is in position, the motor stops trying to turn it, and therefore the noise would stop once the door was in position no?

Take a look at the Factory Service Manual and try using the diagnostic mode of the climate control system:
http://www.nicoclub.com/FSM/Pathfinder/ ... der/ha.pdf

The diagnostic mode will tell you an error code and how to remedy it.

Yes I did look at the Manual before posting, and I plan on trying the diagnostic mode this week. Thanks for the reply!

[Hawairish]

If there's some obstruction/breakage that prevents the blend door from completing it's motion, I'm not sure how the motor or controller would know it was in correct position to stop trying, if not by some sort of sensor (switch, optical, etc.). My hunch is that it will work until it gets a signal from that sensor, rather than relying on some sort of "memory". I suspect this because the self-diagnostic mode for the climate controller has the capacity to test each position.

That's why I can imagine some worm gear in the blend door motor just spinning and clicking.

You should be able to remove the blend door motor ("mode door motor") relatively easily from the driver's side footwell under the dash without having to remove any other part of the dash, according to the FSM. With it removed, you should be able to move the door by hand, as well as cycle the modes via the climate control to see if the motor responds correctly (and adjust the door by hand to see if my sensor theory above is true).

And sorry for the "should" responses above...personally, I've not had this problem on my Pathfinder, but I have had this near-identical problem (and resolution) on another vehicle I own. For me, it was just some binding on the housing...must've been kicked or something.