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Just replaced the thermal fuse. Went from no blower to blower always on high. Green Rear Manual control light is on in the front controls. When I push that, I can switch from the top vents to the floor vents using the rear controls, but the fan speed never changes and I cannot get the blower to ever turn off. It turns on as soon as the key is turned. When I turn the AC completely off, the rear blower stays on full blast. For now, I have the power unplugged to the blower so it is always off.

Do you think a new transistor assembly is needed? I have read elsewhere that when it fails, it can fail closed.

When I replaced the thermal fuse, I just wrapped the wires with electrical tape...I don't THINK there is a short, but I'm not 100% sure. I don't have any of the insulator sleeves.
 

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hmmmm..so i jumped the circut and it didnt work. Fuses are good and ligts on the unit come on. Anyone know how to test the fan without having to pull it out?
 

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The MDXer's on this board are awesome! Just did the clean screen and replaced the transister. 1/2 hour job and "Houston we have the Rear A/C on again!"

Thanks so much!
 

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Thanks!

Thanks to all, just replaced the transistor on my 2004 MDX with 95,000 miles and it's cooling like a champ!:29:
 

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Same Problem $1.50 Fix

I had the exact same problem my rear A/C died and Acura told me it would cost $500 to diagnose and i knew it was the transistor which costs $100 in the transistor there is a heat fuse which burns out at 130 degrees C and mine was burned out. I went to Radio shack and got a new one for $1.50 and soldered it in. it was a bit larger than the original fuse but i made it fit. Its a quick easy fix and i got the idea from this video
 

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2003 MDX Rear AC Fan - Stays On After Changing Fuse - Unable to Control

I just replaced the thermal fuse for the rear AC fan on my 2003 MDX, and now the fan works. But once I turn on the ignition, the fan turns on immediately, on high, and I can't control it. The rear fan control does not respond even though the rear heater control next to it works. Also the option switches for top or bottom (floor) blowing do work. Does anyone have an idea what could be happening? One thing though, I did not reuse the little plastic tubes found on the legs of the original fuse. Does this make any difference? Should I redo the whole thing again and use these tubes on the new fuse? I did not throw them away. I also used enough of the paste though. Or could the problem be the rear AC blower switch? I would really appreciate some help..., thanks!
 

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I am guessing without the plastic insulation you are shorting the transistor. Use a new shrink tubing around the exposed wires of the thermal fuse and try again!
 

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I have a 2004 MDX and the rear air stopped blowing. I replaced the thermal cutoff. now my rear blower runs on maximum constantly and can't be controled. It even runs when I turn the air completley off. Has any one had this problem
Had the same problem (I didn't examine carefully the old one to see that it was insulated). You didn't dress the metalic wire of the termal cutoff with insulating material and that shortens the transistor. You can simply pull the metalic core of an insulated wire and use its insulation to completely insulate the wire of the termal cutof, that will fix it, guaranteed.
 

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Had the same problem (I didn't examine carefully the old one to see that it was insulated). You didn't dress the metalic wire of the termal cutoff with insulating material and that shortens the transistor. You can simply pull the metalic core of an insulated wire and use its insulation to completely insulate the wire of the termal cutof, that will fix it, guaranteed.
Pics here for similar work on a Honda Pilot:
Rear blower Transistor Fix - Honda Pilot - Honda Pilot Forums
 

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After reading the very helpful postings about replacing the thermal resistor, I got adventurous and decided to give it a try. Once I had pulled the thing apart I did find that the resistor was "open circuit", and replaced it. After replacing it back in the vehicle, I was so happy to have "fixed it". Until the next day, when I encountered the other problem mentioned, where the blower blows at full speed and can't be stopped.
Back to the forums, and with a bit of searching found reports of the MOSFET transistor needing replacement. The original MOSFET on the power transistor on the 2004 MDX, was a 2S2313, which now appears to be discontinued. I replaced it with an IRFP064PBF from Digikey (only $4.69 in Canada + shipping ), and its working like a charm (so far).
 

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Thanks to all those who have contributed to this thread. My rear A/C unit was fully reponsive to the controls, but the blower wasn't working. Found this thread, replaced the blown thermal cutoff, and fixed the problem without dropping $100+ for the the power transistor.

The amount of lint of the screen cover for the rear blower was definitely a contributing factor, and is something I'll definitely be cleaning out every time I replace the cabin air filter.
 

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Rear A/C 2007 Pilot Not working

I replaced the fuse on the thermal part 077800-0870 and the blow now stays on all the time. Are any of you having the same problem? Let me know how you fixed it. I replaced it with an EYP-2BN110 thermal cutoff switch. Even when I took it off and connected the part back it still stayed on. What gives? Need help. I don't really want to fork out $90.
 

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So my "New to Me" 2004 had the same dead rear fan issue so many of you have had.

In reviewing this thread, and looking into the thermal cutout I pulled mine apart. I am not a degreed Electronics Engineer, I took the easy road, and only took the two year applied Electronics degree, so I don't know everything, but I think I have a bit of added information for you.

In my vehicle I found that the Thermal Cuttout had a different rating that those mentioned before. I speculate that this is a result of either of two things. 1.) my original factory installed unit, was late enough to have a redesigned Transistor, or 2.) Acura did a redesign as a result of the multiple failures after my vehicle was built, and it has been changed at least once.

My Thermal Cutout is an N126 model, with a cut out temp of 133* C somewhat more that that of the other N109 models that have been discussed, which are at only 110* C.

This lead me to believe that maybe the amp draw is not that important as the thermal rating, so I measured my fan current draw to be no more than approximately 250ma at full speed, and no amount of airflow blockage made any significant change to the current draw. Normally fans do draw more current when airflow is blocked, but maybe not in all cases, such as low total CFMs, or DC powered, I don't know, that is for another time I guess.
It is still possible that the lower CFMs of a clogged intake screen could contribute to less ability for the heat sink to reject heat from the thermal cutout, and it rises above it's design limit.
Either way a clean screen is still a great idea.

The reason I originally thought to post here, was to throw out the newer ratings I found on my unit. It doesn't appear to have been modified, as the solder joints are factory, although it is possible, since a skilled technician can replicate factory joints.

I do want to thank you all for this idea, I generally just replace OEM parts with OEM parts, and I don't typically try to rebuild, or repair them. Not this time, just too easy to swap the cutout, and it saves me about oh $87 bucks.
 

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Hi a quick thanks to all the posts here I was able to replace the thermal cutoff transistor. Instead of taking the more fun route, I opted for ordering the replacement for $16 in Amazon and it worked like a charm. Until the kids break it again....they have their own air for now :))
 

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After reading this thread from the beginning and not the last page I went and pulled my transistor assembly. Yes the fuse was measuring an open. I decided to remove the thermo fuse and replace it with a jumper wire. Cleaned the screen and reinstalled.
Everything works like it should now.
It cost me nothing to fix it this way but after seeing you can now purchase the transistor assembly via ebay or Amazon for around $20, I might still go that route.

My thanks to everyone who contributed to this thread. It is very well one of the easiest DIY fixes out there.
 

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No rear HVAC

I've gone through this thread and haven't seen anything that matches my situation.

The front heater/AC works fine. The light on the RR A/C button on the front console lights up when it's pushed in. The lights on the buttons on the rear console never come on at all no matter what buttons are pushed. To me that says there is no power going to the rear unit at all.

I've changed the #3 fuse in the underhood fuse box, and changed the transistor in the console. I haven't changed the #52 fuse in the driver side panel because the way I read it, if it was blown, the front blower wouldn't work either.

The buttons on the rear console still don't light up, and the rear blower still never comes on. I got the transistor on Ebay for $12 - could it be that a cheap knockoff part being defective out of the box is my problem?

Any ideas?
 
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