Dead Gen2 Blower Motor (intermittent) (bypassed, DIY inside)
  • Well, it only took two weeks for my cubic to break something. Yesterday: frigid polarbear air conditioning. This morning: no fan whatsoever. both fuses are good, and the digital controller is happy. Guess it's time to tear into the dash, get to the motor and resistor, and try to sort it out. I've looked around a lot on here and found nothing too useful. If you have helpful info, please link to it rather than 'in the xxx forum'.
  • if all the digital control functions 'work' it's probably the heater resistor.The part number is N27761AX000 & I think its a pretty easy swap out.Look on you tube under nissan heater resistor
  • Its located side glove box. If you have an Auto Climate model then the part is made by Valeo and is the same as used on many Peugeot, Citroen and Renault models. Easily obtainable on Ebay at fraction of Nissan price - think we paid around £35 for a new non genuine part.
  • CID, are you saying the blower is behind the passenger side glove box? I got a lot of the dash dismantled last night before dark, but have yet to get to the blower plug to test power to it. I found and electronic service manual for the Micra, and it's right-on so far.

  • Anywho...After dismanteling the dash, I found out that the auto controls have a diagnostic mode. Everything checked out just fine, and after going through the diagsnostics, it works just fine again. For reference, start the vehicle, and hold the OFF button within 10 seconds until all the lights and LCD segments light up. then use temp up/down to cycle through the 5 diagnostic levels, and DEF to cycle throught the functions of each level. It's detailed in the micra service manual for those that have it.
  • And, as with all things that mysteriously fix themselves, I put the whole dash back together, reset the airbag light, and then when I drove in this morning the fan refused to work again. Grrrrrrrrr.  Should you need to reset your airbag light because it's flashing, do this: Turn the key to ignition, and when the solid airbag light goes out, turn the key off and wait five seconds. Do this four times and then start the vehicle. All done.
  • Nice tip about the heater diagnostic mode. :)


    (And the airbag reset too but I knew that one)

  • Yep, saw that. Isn't the fan blowing on high or nothing a symptom of the resistor pack failing though?
  • From my experience, problems with fan speed are a failure of this blower resistor.
  • So...They ebay calls it the 'blower resistor' but the manual calls that the fan control amplifier....and It bet that IS the issue. Back out to the cube with the meter...



    Thanks CID.

  • Hi. 

    Our fan has also stopped - on all settings. I understand from reading around Micra forums that when it is the resistor, the fan works on max only.

    Interested to see if the resistor works for you..

  • I'll post back and let you know Stu. I've got the glove box out right now and it's exposed. The a/c didn't want to work this morning, but when i tapped on the resistor it fired right up. I'll order one in a moment, but it takes a while for things to get here on the slow boat, like 4-6 weeks.
  • Thanks for that. Completely missed that you are in JP.

    I'll likely be having a dig soon so will post up on this thread with what I find.

  • So... my blower came back on without me touching anything.  One thing.. we have very messy wiring hanging down near the pedals (that I have to sort soon).  I'm wondering whether something got caught up there.

    If it stops again I'll investigate and post back.

  • I hope it stays fixed. Mine still likes to take every other day off.
  • With all the typhoons, I need the defroster so I can see to go to work. Still waiting on the part to come it, from China, to the states, to Oki. aye.


  • No direct shipping from CN to JP?

    Update on mine: blower works in manual mode, but not Auto. We can live with that so I'll make do for now and dig around after winter - unless manual operation stops again.
  • I have a military mailbox, so it has to go through the states to get to me.

    Have you tried the controller diagnostics yet?
  • So, first of all, hats of to CID. It's fixed thanks to your advice.


    I took the old 'blower resistor' out, put the new on in, and voila. I've found in other locations that there is a particular component prone to failure that can be replaced if you don't want to buy the whole module. I may repair mine just in case, but I was able to get one for $22 shipped. So again, thanks CID. Thank you very much. I can live without the A/C this time of year, but we've had typhoon after typhoon, and my windows tend to fog a lot. Now I can see again!

  • Thanks for the follow-up.  

    I did run through the diagnostics but the codes that came back were a bit generic.  I might run it again now the manual mode is working.  If it dies again I'll get a new resistor.

  • And today, auto mode started working again. I'm sure this car is alive!

  • Blower has stopped working again - not handy in this weather!  

    So, resistor purchased and fingers crossed!
  • Good luck!
  • I ordered the new resistor and the next time I drove the car the blower worked again - magic! ;)
  • Aye, and she'll keep working until you realize that the part is going to take 2 weeks longer than expected because you ordered it from xyz, and then she'll quit forever. You'll finally pull the bad one out wondering the whole time if it was worth the money, and probably plug it in before you bolt it on to try it, and voilla. Then you'll kick yourself a bit for putting it off in the first place, and maybe vow to have a spare on the shelf for the future...

    And FWIW, mine was on and off again like yours until it finally quit. I'd bet you'll be right as rain after a swap.
  • Thanks - I hope so.  :-)

    I'll take some pics as I go for future ref.

  • New resistor arrived today.  Before fitting, manual worked but auto didn't.  After fitting the new one.....

    Neither manual or auto worked!

    Refitted the old one... manual worked again.

    Annoying! :-(
  • That stinks. What next, a different controller?
  • Yes, it stinks! :-(

    I'm back to keeping fingers crossed it keeps working in manual mode for now. The part I bought was repro, not original Valeo and the plug fit was tight. It might be a duff one...
  • Well, I finally got around to ordering a replacement mosfet for my dead fan control amplifier (aka resistor pack). Just for the (my) record, I ordered HUF75344G3. It was 3 bucks. From what I read it's the part that goes bad. I'll get the other one replaced so I have a spare just in case.
  • Hi,
    Do you know if the resistor can be tested with a meter?
  • copied from how to mend it dot com, and it's about a clio, but the parts close if not the same. This is how you test the vehicle. I'm sure I've seen something somewhere on how to test an N-type MOSFET in-circuit. I'll look. Below should be just as good. You'll just have to tease out what is meant by the AC Fan Unit. What is commonly called the 'resistor pack' on here is called the AC Fan Power Unit below.
    With Ignition still set to ON, check 12V is now present on both terminal 4 of the Air Conditioning Fan Power Unit (61) and terminal 1 of the Air Conditioning Fan Unit (62).
    Check for earth on pin 5 of Air Conditioning Fan Power Unit (61) Note:- the pins are numbered 1-5.
    Disconnect the connector from the fan power unit and then, with ignition ON, temporarily link together pins 1 and 5 of the free connector socket..With the link in place, the fan should run at full speed - if not the fan is faulty.
    To check for correct operation of the Air Conditioning Fan Power Unit (61), which controls the speed of the fan in response to signals from the Air Conditioning Unit(56) and the fan speed controller, perform the following sequence:-
    With the Air Conditioning Fan Power Unit (61) reconnected;-
    Check the voltage between earth (chassis) and pin 2 of the unit (this is difficult to access due to the compact nature of the wiring). It should vary as follows
    speed 0 13.94v
    speed 1 11.36v
    speed 2 10.17v
    speed 3 8.93v
    speed 4 7.69v
    speed 5 6.34v
    speed 6 5.13v
    speed 7 3.8v
    speed 8 0. 1.4v

    If it does vary as detailed (approx voltages), then the Air Conditioning Unit(56) is operating correctly. If the fan speed does not vary in sequence, or the fan speed remains constant, then replace the Air Conditioning Fan Power Unit (61)

    Repairing the Air Conditioning Fan Power Unit
    The following instructions are offered to those with basic experience of electronic circuit repairs:-
    Open bonnet then, remove drivers side scuttle cover (remove wiper arms with blades if necessary. Unplug large plug with black wire to fan then remove securing screws. The device sits in the air passage with a large aluminium heat sink on it which is cooled by the air passing over it. At first glance, it looks like a 5/6 way connector bolted to the air passage but it's actually inserted into the airway. Dismantle the casing then peel away silicone sealer from the soldered side of circuit board around the power MOSFET device. De-solder and then remove the MOSFET.
    Caution: The power MOSFET device is very sensitive to damage caused by static discharge. Ensure all items. including hands, are grounded before they come into contact with the device leads.
    The original power MOSFET fitted is normally a 75344G3, 75A, 55V device, but this item is no longer manufactured and is therefore difficult to obtain. The best, easily obtainable, equivalent is currently available from Maplin, and is a Fairchild type HUF75337P3 at a cost of £1.95. This has an identical power specification but a slightly higher Drain/Source resistance (0.014 Ohm compared to original item’s 0.008 Ohm). The P3 suffix, however, indicates that it is in a TO-220 package in place of TO-247 necessitating that the clamp is ‘closed’ slightly, before fitting the new item to give it a secure fit. Pin connections are the same so, when fitted securely in place, solder into position. Replace any silicone sealer removed during disassembly.
    Note: If a HUF75337G3 or a HUF75344G3 can be obtained, then the suffix G3 indicates a TO-247 package which is the same package as found on the original device. However, Maplin do not currently stock this latter item. Another alternative but identical device, which is currently manufactured by Toshiba is a 2SK22987 which is in a TO-247 package. This item is distributed by Harris. A more modern near equivalent, with very low Drain/Source resistance of 0.005 Ohm, but in a TO-220 package, is an STB80NF55-06.

  • Power MOSFETs most commonly fail by shorting Drain to source. Our N-type MOSFET pins from left to right are Gate, Drain, Source. Try checking for a short between pins 2 and 3, the center and right pins when looking at it from the side NOT touching the heat sink.
  • Wow - many thanks for that, much appreciated.
  • Don't thank me yet, nothing is fixed! BTW, have you found yourself a copy of the Micra electronic service manual to use yet?
  • Yes - I have the Micra ESM.  I did the diagnostic procedure from there - mine threw a '25' error but this is something to do with sunlight detection I think and might be due to running the tests in the dark.

    I'm loathed to play about with it for now as it is currently working on manual - and would at this time of year be practically undriveable without a fan.  If it dies completely again, I'll start playing.  

    I was actually thinking of testing the resistor pack I bought as it is really odd that installing that stopped everything working..
  • I keep forgetting it's winter out there in the real world. Here, we are in the only season where you can live without a fan.

    Fyi, I if you can figure out which harnass is for the fan power unit above, it says it runs full speed when you short pins 1 and 5... :-)
  • For reference, the specs for the original MOSFET (W8NF55-08), and the current, in production replacement (HUF75344G3) are attached.
  • Here are pictures of the Valeo part with the plastic cover and the copper clip that holds the MOSFET to the heatsink removed. I tested mine for a short form source to drain and don't have one. Several of the solder joints have small cracks, and the plug that brings in power to the module has a contact that's almost missing solder completely. It looks like quality control was an issue when this was Morocco (which should be no surprise as they fail so commonly I guess).
    2688 x 1520 - 948K
    2688 x 1520 - 461K
  • Excellent information roswell.

    Thanks :)

  • Hey Roswell. I forgot to ask earlier.. did you find removing one of the heater resistors to be a pain? One of the plastic airways makes access tricky...
  • I don't remember, honestly. I do remember one fastener was a pain to get started and tight, but which one I don't recall. I just remember I had to borrow a Leatherman from someone because I was out in the parking lot with only a handful of tools.The plastic airways are a pain, no matter what. They always seem to be in the wrong place at the wrong time.
  • Thought I'd continue my woes of the dead blower in this thread rather than start a new one - hope that's ok..?

    So, ours has now stopped working altogether making the car largely undrivable during cold evenings.  I have this temporary fix:


    Not ideal, but will do for now.

    Next attempt to resolve is to buy a proper Valeo resistor - I'm not convinced that the one I bought is right/works.  With this in mind...

    Does anyone know the part number for the original Valeo resistor pack?

  • What type of ac have you got ?
  • Auto dude.. (sorry, should have said)
  • Thanks Roswell - much appreciated
  • So, here is my original Valeo unit:


    No sign of any of the part numbers I've seen listed elsewhere.

    This is the new (non Valeo) one:


    The plug gap is 6mm versus 7mm on the Valeo.. That made for a horribly tight fit - I'm not sure it plugs in properly.

    Our old one is back to working on manual - it stopped, but wiggling the plug brought it back to life.

    Old (top) and new (bottom) side by side:

    I don't understand the long solder lines underneath on the new one (left):

    I'm now tempted to send the old one to a fixer on eBay (my soldering has always been a bit ragged so for £10 it would be worth it!).
  • So, decided to plug new one in again and make sure that plug was pushed in ok... and it's working!  Auto, manual, the whole shooting match! :-)
  • Dear Lord. I'm so happy. You still have a few months of winter left don't you? The wide solder lines are probably because the work was done by hand instead of machine. How much does the fixer want?
  • Thanks for your help on this Roswell. I now know much more about MOSFET.

    20c here yesterday but every chance it could turn cold again.

    Fixers on eBay want £11+p&p..
  • Looks like at a board fix, seen it done on pc motherboards where a board is damaged between locations and they bridge the broken section with solder or with a random length of wire.
  • Thanks Terry. A quality item then! :-)
  • Well, mine died again while the wife was driving it and I was out of the country. I pulled out the the old fan control amp I replace, and soldered in the new MOSFET. That got the blower motor up and running (too bad the replacement one didn't last...), but the compressor doesn't want to kick on. The theives at the local shop wanted $1100 to replace the compressor and a hose, but I suspect they were playing gouge the wife. It happens around here. Man what I wouln't do for a few minutes with a CONSULT-2. Now I've got to sort out why the compressor isn't coming on. I suspect my aging cube developed a leak, and the pressure switch isn't giving proper voltage to the BCM, but who knows. If I'm reading the manual correctly, the BCM and/or a/c controller either 1) isn't getting the signal that the blower motor is on, 2) isn't getting a good pressure signal, or worst case the BCM is shot. Wish me luck.


  • Hi Roswell

    Regarding the CONSULT-2 comment have you seen the other posts about the diagnostics plug-ins you can buy?

    Good luck with your thermostat.

  • No, I haven't, thanks! I'll dig around. The search on here doesn't like me much, so feel free to post some links if you get bored!



    I've found something interesing on fresh and minty!

  • I'm losing my patience. My newly repair fan control amp lasted all of about two hours and now the fan has quit again. I don't know if it's getting spurrious inputs or what, but this is out of control.


    -edit: I swapped out the old 'bad' Fan Control Amp (FCA), and the fan came on. Then I swapped it to the new one...and the fan came on. Tore the dash apart to check a couple of circuits and no fan. Swapped to the old worked. Swapped to the new still worked. I sure wish I could figure out why oh why the blower decided to work some times and not others. I'm ready to leave this thing in a bad area of town with the keys in the ignition.

  • It must be a dodgy connection or switch somewhere? Fan itself faulty even?
  • Sticky brushes in moter have a lot ov that in daf trucks if you can get to see them
  • And ours has died again too! :(

    Slightly different symptoms this time - everything seem to work bar the fan.  Eg, set the temp to 18C and the fan bar display goes up to 3-4, but no fan.  Manual, auto, nothing gets the fan going.

  • I tracked mine down to a poor connection in the 2-wire plug that goes into the fan control amplifier. It has been drawing enough current to heat up and melt the plug. Not sure of the cause, but it's not good. Maybe I should keep a fire extinguisher handy from now on.

  • Just an update on ours. I sent the original Valeo resistor Card off to the fixers..
    They tested it and said all working fine! So, back to the drawing board. I reckon it's the blower fan itself, so time to rip that out...
  • well, we seem to have the same problem: a unpredictable, intermittent blower. I just hit all the wrecking yards (breakers for some?) and got the wiring before the plugs and fan control amp aka 'resistor pack' from two cars. I found quite strangely that someone had rewired one. At least, I thought it was strange until I realized that they had spliced the hot source in to the blower's hot wire, so they had key on=fan on. I was going to put a relay and a switch in as a last resort, but this was pretty cheap too. My problem is still crappy connections where the plugs enter the FCA, so I'm going to splice good --not melted-- plugs onto the wiring harness in the hopes that this will be the cure. Right now, the wires are hot to the touch when the fan is on high. Common wisdom says that wires only get that hot, provided they are of the correct gauge for the load, if there's a poor connection at a joint. fingers crossed. Failing that, I'm just going to mod the fan for full blast. It's not like they're that strong to begin with.
  • Sounds familiar. Having got so much of mine apart I could see that the last run of cables to the FCA is wrapped in standard electrical tape rather than automotive loom wrap. Looks like someone has been here before!

    I found another random off/on switch behind the mirror controls. No idea what it is for but proof that there is plenty of non standard mods here.

    I think I have mine licked (see other thread) - if that's not it I've already bought a relay and switch for manual operation.
  • Well, mine continues to be a serious pain. After splicing good plugs back on, the aircon lasted a month and started acting up again. This was okay when I was driving it, but my wife claimed the car AND my parents are in town while I myself are away. It's hot out. I'm going to order a NEW not used blower motor and swap it out. That's just about all that can be left at this point, and probaly what was causing excessive draw, and wires melting.
  • For anyone whose still interested...the short version. I put the new fan in, and while it did blow slightly better because the fan was not dirty, it changed nothing. I ripped the dash apart again, and traced every connection to no avail. Intermittent connection issues are torture. I did find that the red wire was overheating at the connection to the fan control amplifier, and was causing the connection to go bad...this time. I managed to smash the connector down smaller so that maybe it will hold fast and not overheat. However, I'm done fighting this thing. I live on a sub-tropical island, and the fan only needs one speed:fast as it can go. So, I wired in a bypass switch.

    Now for the geeky bit: the fan control amplifier (FCA) is built around a semi-conductor that provides variable conduction. What's supposed to happen is as the brains of the automatic AC command more or less fan speed, that small current is translated into a better or worse path to ground for the fan. Yes, it seems a bit backwards. So, with the ignition on, and the AC turned off, the fan has 12V+ AC, but no path to ground, so it doesn't turn. As the AC controller steps up the fan speed, it sends a higher voltage to the FCA, but when that voltage gets to the semi-conductor, the voltage causes it to open the path to ground, allowing the fan to run faster.

    So, how to bypass the whole thing and get on with it:

    First off, the 3 wires you should concern yourself with are the red, yellow, and black. Yellow is ignition power to the fan, black is ground, and red is path to ground from the fan. So, what I've done is wire in a SPST switch with splices rated for 25A I  had lying around. The AC is working just fine on automatic, but if the last 14 months have taught me anything, it's only a matter of time. When the switch is closed, it connects the red wire to ground, allowing the fan to use all 12v, and the fan blows at full speed. You can ignore the fact that I have 2 pairs of wires running from each one. I didn't have any wire of sufficient gauge for the 15A circuit, so I doubled up what I had.

    1118 x 632 - 94K
  • Excellent technical detail in this thread.  

    Cheers @StuM and @roswell :)