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Automatic AC - Blower Intermittent

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Hey gents,


Last couple of times we've gotten into the 2001 Pathfinder LE - the Blower has not started. We can see the blower "fan blades" filling on the automatic air conditioning screen- so it appears to me the controller is asking for the fan to turn on. It doesn't matter in manual load if your set to speed 1 or 4, the fan doesn't start.

It will occasionally turn on after about 2-3 minutes of driving. The fan sounds perfectly normal if/when it eventually comes on, and the AC will work normally the rest of the trip.

In other vehicles in the past, I've replaced both Blower Fans and Resister packs, so I am familiar how manual AC works and some common failures.

The fact the fan does eventually come on and runs normally, leads me to believe its not necessarily a blower problem - no squealing or speed variations etc.

The fact that once the fan gets going all speeds are available, leads me to not a resister pack issue either - as that usually is the result of just the full speed working and no other speeds. Does this use a traditional resister pack or something else?

Possibly a head unit problem? The fact the head unit shows the speeds being called for leads me to believe head unit is good.


Any help is appreciated, thanks!

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My fan did that for a little while when it was going out, but quickly got worse.

Automatic ACs use a PWM controller driving a high power transistor, in place of a resistor pack. They generally call it a blower amp. I believe it is in the same area as the resistor pack on the R50's sitting in the airstream because they do generate some heat.

Sent from my SM-N950U using Tapatalk

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Yep, the auto climate uses the blower amp instead of the traditional resistor. It is mounted next to the blower motor and has a a larger heat sink because it does run hot. With your symptoms, that is where I would suspect the problem to be. 

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Threw the new amp in it - also new cabin air filters - I didn't realize R50 had CAFs - test drove it - seemed fixed.


Fiance drove it the next day and reported no AC. I got in it, drove over a speed bump, and had AC again.  I've got the glove box off and going to have her wiggle wires next time it fails. I can't make it stop wiggling either the amp or blower wires. 


I love intermittent issues. So much fun. I've got a blower and a wiring harness coming too...

Edited by Inyourface1650
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  • 2 weeks later...
On 8/11/2019 at 4:49 PM, colinnwn said:

I probably would have replaced the amp first too. Now it certainly sounds like blower bearings or brushes are toast and binding.

Sent from my SM-N950U using Tapatalk

Yep, seems it was the blower. 

I replaced with a cheapo $32 unit from Amazon, and while a bit noisy, it certainly pushes a lot more air, and seems to be starting reliably.

Finally able to put the dash back together after two weeks. 

Call this one closed. 

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