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Update. Issue Resolved.

I went back over the OP's steps. I did not insult the wires coming from the resistor.
I took it apart and wrapped electrical tape around them so it now looked like the old resistor.

Reassembled and it works!

So insulating those wires is apparently crucial to the repair.
 

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Rear blower thermistor

I knew about the issues with the rear a/c on these vehicles years before I became the owner of the new to me 2003 EXL w/RES. One of the previous owners had already replaced the thermistor and it only lasted a couple of months before burning out (its hot in the deep south!). I guess enough time has passed since the issue was first identified that now there is an improved thermistor assembly available. The part was $56 on eBay and took about 5 minutes to install since it was an even swap for the defective part. The rear blower screen was still clean as a whistle considering the rear a/c was hardly ever used. The improved part uses a larger heat sink that is curved rather than square shaped, giving a better heat dissipation than the original part. I replaced it exactly one week after purchasing the Pilot back in March and have had no further issues with it.
 

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There is another forum thread calling for 667-EYP-2BN127 (Panasonic) here: http://www.piloteers.org/forums/14-problems/18622-2003-pilot-rear-c-controls-back-seat-passagers-not-working-5.html#post396999

I see someone using 667-EYP-2BN109 above in this thread.
Can someone please confirm which thermal cutoff we need?
Unfortunately I already ordered and will need to cancel immediately if I ordered the wrong part.
Thanks,

EDIT: Inspecting this and other forum threads led me to the correct part: EYP-2BN109
It is $4
.33 from amazon here:
http://www.amazon.com/Panasonic-EYP-2BN109-Thermal-Cutoff-250VAC/dp/B005T5Y5Z2%3Fpsc%3D1%26SubscriptionId%3DAKIAILSHYYTFIVPWUY6Q%26tag%3Dduckduckgo-d-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB005T5Y5Z2
 

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So, let me tell you my sad tale. The rear blower in my 2007 EX-L stopped working. After reading through this thread (and others) about the thermal cutoff fix, I popped out the transistor, removed the cutoff, and replaced with the recommended Panasonic part. Cleaned the intake screen, replaced the transistor, and... no joy.

At this point, I went back to where I SHOULD have started, and did some troubleshooting. I checked the resistance across the original thermal cutoff, and it seems like it was fine from the start. Suspecting the blower motor, I popped the passenger side trim panel and removed the harness from the motor. I checked the voltage across the two wires in the harness and got 13.4 volts. So, if the motor was getting 12v+ but still not running, clearly the motor was bad. It looked like an OEM replacement would run $200+, but I was able to find one at a local salvage yard. Popped it in, and... no joy.

Unless I'm missing something, the "new" motor must also be shot, correct? If I'm getting 12v across the harness, the motor should run, regardless of whatever else might be wrong in the system?

As a bonus- I think I must have bungled the transistor "repair" as well. I noticed I got 12v+ across the motor harness NO MATTER WHAT the setting was on the climate controls (including OFF). I assume that means that when I do get a good motor in there, I will have the problem mentioned by other posters where the motor runs at full speed, continuously, regardless of settings. I guess that means I have a short in my transistor? I did cover the entire length of the leads with heat shrink tubing, but must have muffed something else.

Would love to hear any suggestions anyone might have...

Thanks,

Randall
 

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Consider me now 100% baffled. I took the original blower motor I removed and connected it to a 9-v battery- it runs fine.

I don't get it- with the wiring harness unplugged from the motor and engine running, I get more than 12v across the motor wiring harness. I pop in the motor- it doesn't run. How can this be? What am I missing?

Thanks,

Randall
 

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Yes- I tried running the system on "AUTO," with temp set to "LOW," and also tried setting the rear air controls to "RR A/C MANUAL" and manipulating the controls on the rear of the center console.

I tried plugging the wire harness to the fan without reinstalling the fan itself so that I could see for sure if/when the fan was running. Interestingly, it runs for about a second when the ignition key is first turned- then shuts off.

Also, I am pretty ignorant about automobile electrical systems, and I think I may have been measuring the voltage in the harness incorrectly. There are two wires in the harness- one solid blue, one blue and yellow. I started by measuring ACROSS the two wires, getting around 13v. I then tried measuring from each wire to the chassis (ground), and found that the blue/yellow wire read a consistent 14.3v, and the solid blue would vary with the fan setting, from 1.06v (highest) to 0.92v (lowest).

Google took me to this thread, which seems relevant, though I'm not sure how to interpret the results?

http://www.justanswer.com/honda/66v4u-honda-pilot-ex-l-rear-blower-not-working-tried-new-transistor.html

Have any of you ever measured the voltage at the blower motor harness? Do you have numbers to compare for a correctly functioning fan?

I have to admit, I'm still puzzled that the fan can have voltage across it but not run.

I wonder if my issue is with a component on the power transistor board other than the thermal cutoff? I also found this thread on an MDX forum suggesting that the MOSFET transistor itself is subject to failure:

http://www.mdxers.org/forums/73-2001-2006-acura-mdx/76073-rear-blower-fan-malfunctioning-mdx-2004-a.html

Might be time to replace the entire power transistor instead of just the thermal cutoff. Any ideas would be appreciated, though!

Thanks,

Randall
 

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my rear a/c transistor looks totally different from all the ones posted. we have a 2007 honda pilot. it is square, not round like the ones shown here or on youtube.
 

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I did this fix back last year August and it went out again this past week. I'm not sure if it was an inferior part or not but am needing to do the fix again!! The info you have here is great and informative, too bad I found it "after" I did the fix last year. LOL

I have a question about putting a jumper wire in though. Is that a safe/good fix or is it not a good idea to do???
 

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It's safe. I have my jumper since 2009 with 115* las vegas summers. My mother-in-law also had hers till her transmission failed 2 years ago. The thermal fuse idea is so stupid. They should simply use a thermal protection circuit that shuts the unit off, but allows it to come back on once the unit is cool. This feature is found in every cheap RC car transistor speed control since 1989. Why they didn't put it in these fan controls is beyond me. Probably saves 32 cents per unit over millions of cars.
 

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I'm still puzzled that the fan can have voltage across it but not run.
Answer is actually simple. Most fan motors need a large current "kick" to get started. Usually there is a start capacitor somewhere inline to the fan electrical to give the starting torque needed to move the fan from stop. Once it is running the line voltage keeps it moving. Had an A/C fan for home A/C loose this start cap....I only needed a nudge from my finger to begin moving the fan & then line voltage would run it...w/o the starting cap (only had like 33 uFarrad on 120V) the fan would never start up!
 

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This is a great thread with a great fix, and thanks to the OP. I'm usually the first in line for a 75¢ solution, and in fact I even ordered a 3-pack of those thermal resistors just as insurance even though my HVAC is working flawlessly.

That being said, at this point there are at least a couple of other good options.

  1. Just jumper it. 94eg!'s experiences have stood the test of time.
  2. Back when dealers were charging a couple of hundred dollars or more, the soldering solution made sense, but especially for those who aren't exactly a Jedi knight with the soldering iron, it may be easier and not too extravagantly priced to just switch out the unit, which now goes for about 13 bucks on eBay: Rear A C Blower Motor Transistor Resistor for Honda Acura MDX Pilot 79330S3VA51 | eBay
  3. Just making sure you keep the rear blower fan unclogged will usually preclude or at least greatly postpone the chances of it overheating and blowing in the first place: http://www.piloteers.org/forums/69-2003-2008-pilot/89346-05-ex-rear-vents-blowing-weak.html#post921938
 

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Thanks to this thread, I identified the source of my '05 EXL rear AC problem and replaced the "Blower Motor Resistor" (Honda's description) with OEM part no. 79330-S3V-A51. Just to satisfy my curiosity, I measured the resistance between all pin pairs on the new part and the defective one, as shown in the table below.

Resistance
Pin Pin New Defective
1 2 11K ∞
1 3 ∞ ∞
1 4 1.06M ∞
2 3 ∞ 6.8M
2 4 ∞ 6.8M
3 4 1.5K 1.5K

This was NOT a functional test but it's pretty clear the two parts have different electrical properties. Just FYI.
 

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It's been a few years since I fixed my rear blower issue. So I decided it was time to pull that trim panel and vacuum the screen again. Yep, the screen had a fair amount of lint inhibiting flow again. But at least I caught it before it failed this time!
 

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First off, thanks to piloteers for being a key part of the google fu routine I've used to repair whatever has gone wrong on my wife's rig for the past several years. This thread is no exception... Thanks dudes!!!:29::29:

Now for my first post... always tldr for me lol.

This is a great thread with a great fix, and thanks to the OP. I'm usually the first in line for a 75¢ solution, and in fact I even ordered a 3-pack of those thermal resistors just as insurance even though my HVAC is working flawlessly.

That being said, at this point there are at least a couple of other good options.

  1. Just jumper it. 94eg!'s experiences have stood the test of time.
  2. Back when dealers were charging a couple of hundred dollars or more, the soldering solution made sense, but especially for those who aren't exactly a Jedi knight with the soldering iron, it may be easier and not too extravagantly priced to just switch out the unit, which now goes for about 13 bucks on eBay: ...Rear A C Blower Motor Transistor Resistor for Honda Acura MDX Pilot
  3. Just making sure you keep the rear blower fan unclogged will usually preclude or at least greatly postpone the chances of it overheating and blowing in the first place: ...
Please, don't advise folks to do very risky things without having sufficient expertise to know risks involved! Granted, one anecdotal experience should not be enough to convince others to hack their pilots, but just in case they're thinking they are also smarter than Honda's engineers...

I have enough experience with circuit design to understand why the fuse is a necessary safety item. We're talking about having a way to stop current should that MOSFET fail (in fact it's a K2313 n-channel mosfet, not a 'transistor'... lol so much misinfo on the net). N-fets fail in the 'ON' state. So depending on your failure mode, without that fuse you could end up with enough current running through wires to burn insulation... most folks know that's definitely no bueno. DO NOT shunt!!! In fact, even if you're just replacing the fuse, you best know what you're doing when it comes to keeping the fuse leads from eventually shorting on the fet tab or heatsink (requires intermediate jedi soldermanship... it's not joining 2 solid copper wires, nor is it SMD reflow... but in between those 2).

It's safe. I have my jumper since 2009 with 115* las vegas summers. My mother-in-law also had hers till her transmission failed 2 years ago. The thermal fuse idea is so stupid. They should simply use a thermal protection circuit that shuts the unit off, but allows it to come back on once the unit is cool. This feature is found in every cheap RC car transistor speed control since 1989. Why they didn't put it in these fan controls is beyond me. Probably saves 32 cents per unit over millions of cars.
What I said above about the safety of shunting still applies, however...

I did consider a resettable thermal switch idea for my wife's rig. In fact I happened to have some spare 120C micro thermostats I bought for another project; I'm a geek what can I say? The thing is the t-stats are a much larger square form factor than the stock fuse (they're about half a TO-220). So I'd have to grind the heatsink to fit, which may interfere with the Fet's thermal junction. I just couldn't reason myself to carry out the mod. The only real benefit: it would let me wait another 10years between cleanings without worrying about dealing with solder/TIM again. Now that I know about the screen getting clogged with dust, I'll be cleaning it every other year for my kid's sake (takes all of 2 minutes to clean out, including panel R&R). I just ordered some fuses instead.

Now why would Honda use a fuse vs switch? The avg fuse is $0.70, the average thermostat is $2.50... retail cost but likely scales the same for Honda. Saving that times millions of cars would sure make their investors happy. Heck, even 32cents per pilot would make them pretty happy. Honda didn't write the rules for the game though... can't really blame them.

What I am blaming them for though, is not having the screen cleaning in the maintenance schedule... not even a TB for the dealerships after they saw their first rounds of warranty repairs?!!! Dummkopfs!!!

There is another forum thread calling for 667-EYP-2BN127 (Panasonic) here: ...

I see someone using 667-EYP-2BN109 above in this thread.
Can someone please confirm which thermal cutoff we need?
Unfortunately I already ordered and will need to cancel immediately if I ordered the wrong part.
Thanks,

EDIT: Inspecting this and other forum threads led me to the correct part: EYP-2BN109
It is $4
...33 from amazon here:
Yep, I also almost tripped on that one. My wife's OEM rear blower 'transistor' had a 133C, 2A/250V fuse installed. The 'latest reputable advice' given on this thread would lead most folks to strap on a 109C fuse, where as they should be ordering the 127C version Panasonic N series fuse (much closer to OEM when you look at the datasheets). To be clear, folks interested in doing the DIY repair should google this:

EYP-2BN127

...and pick their favorite vendor from the list, or just go to the junkyard and get a plug-n-play OEM unit for cheap (they don't really wear out)... just make sure the previous owner didn't shunt it, LOL.

Cheers,
Kev

[ps: Below is a pic of my wife's stock setup, with "133C" and "K2313" component markings... nvm, apparently I'm not good enough to quote links or post pics yet, LOL. :p]
 

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The replacement part needed - EYP-2BN127 - has been discontinued by the manufacturer with no replacement. However, I was able to find 2 in stock at newark.com and ordered them. (As it turns out, they actually only had 1 left!) I just installed it and now my rear blower is working again. Thanks to all who contributed to this thread.

--
Mark
 
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