Hello Yall,


I have a 2007 Honda Accord 2.0 VP 4D MT.


AC blower suddenly stopped working. I tried troubleshooting with the assistance of the service manual and this website- but I'm stuck.


The blower will not operate on any setting, including high. I've checked the blower transistor, and have the ~1.5Kohm resistance. When I jumped the number 2 wire on the blower motor connector, the motor ran (step 2 pg 21-27). I checked for continuity from terminal 2 to the ground, actually I checked resistance since I didn't know how check continuity on the multimeter and it was near 0 (step 7). When I jumped terminals 2 and 4 (step 8 pg 21-28) the fan ran on high regardless of **** setting, including off. So the blower motor is good, and the transistor is good. According to the next step in the manual, I need to go to the Audio-HVAC display panel 22P.


Before I go tearing into that, am I missing anything else simple? I'm mechanically inclined, but electrons drive me crazy. How bad is it to remove the panel, and if something needs to be replaced in it, will I be able to do it myself? Is this something I want to endeavor upon? or let a mechanic take over from here?


Thank You,
Numaone

 

If you continue the test, it says to go to page 21-50 to test the transistor. Continuity isn't a difficult test. What brand and model volt meter do you have, then we can give you better directions.

A bad transistor is a common problem, and I am guessing that is your problem. I hate suggesting to throw a part at a problem. If you can find one at a junkyard, the expense is worth it.

 

On the blower power transistor harness connector, you'll want to backprobe the Blu/Yel wire to check for power when the ignition is turned on.

Backprobing is either using a backprobe set or using a thin needle or something and making contact with the metal terminal of the connector without piercing the wire in the back of the still connected connector. Care must be taken to ensure that the wiring does not get damaged. You can use something like a T pin, available at Walmart, etc., and backprobe. These pictures are just to give a picture of the concept of backprobing without piercing any wires.

https://www.hondaaccordforum.com/foru...%5D-t-pins-jpg

https://www.hondaaccordforum.com/foru...back-probe-jpg

At the blower power transistor connector (with it still plugged in), with the voltmeter’s black lead touching chassis/body metal ground, use the voltmeter’s red lead to backprobe the No. 1 terminal Blu/Yel wire. Turn the blower fan setting to the highest speed. There should be ~ 12 volts at the Blu/Yel with the ignition turned ON (III). (Blu/Yel wire is a wire with blue color insulation and a yellow stripe.)

Post your results, we are trying to see if power is coming through the Blu/Yel wire from the Audio-HVAC display module to the blower power transistor base. If there is ~ 12 volt power at the Blu/Yel wire, the fan should run. So, this same test will also let us know if it is an issue with the transistor if there is power at the Blu/Yel wire.

 

PAhona and Redbull-1,


Thanks for the response! I totally missed the second half of the transistor test. I'm going to follow the instructions in the manual and disconnect and insulate the number one transistor this weekend when I have some time and the right tools, but a couple curiosity questions. Why does the #1 blu/yel wire need to be insulated from body ground, and why can't I just supply 12 volts with the #1 wire connected still in the connector. (I actually did this before I read the instructions in detail and nothing happened.).


I'm trying to follow the logic from Redbull-1. So if the transistor is good, I'll get 12 volts from Blu/Yellow when I have the fan at max. By removing the wire and supplying 12 volts, shouldn't the fan run since it has 12 volts now, what it normally does? (i.e. the test above). But page 21-50 says if the fan doesn't run when I supply 12 volts, I have a bad transistor. So I'm confused on the logic of the test (although it probably has to do with why I need to disconnect the #1 wire before supplying power).


Assuming it is the transistor, which it probably is, and I'm happy I have anther test to try, can you recommend a sponsor from the site that has good prices on OEM parts?


Thanks Again
Numaone

 

If you do my test, you don't have to do the second half of the transistor test in the service manual. My test is different than the service manual; but, will tell more.

My test is to see:

• if there is power or not coming through the Audio-HVAC display control module to the transistor; if no power, then it may be an issue with the Blu/Yel wire or the Audio-HVAC display control module.
• If there is power, then it may be an issue with the transistor

 

To answer these questions, if the Audio-HVAC display control module is working properly, it will supply power (~12 volts) through the blu/yel wire to the #1 terminal of the connector for the transistor. The service manual test states to insulate the disconnected terminal wire from touching body ground; this is to prevent causing a short.

If you supply 12 volts with the #1 wire still connected and the Audio-HVAC display control module was working properly, you essentially double the voltage; not good.

 

Since you stated you previously applied 12 volts to terminal #1 of the transistor connector with the wire still connected, you may want to check under-hood Fuse #30 (7.5A) just in case.

 

Checked the voltage as redbull-1 recomeneded. Found 12 volts and replaced the transistor last night. The blower worked. However, today, 18 hours later, with the new transistor stopped blowing again! Used Honda OEM part. What gives?

Numaone

 

The transistor likely fails due to either excess current load (bad fan motor pulling too much load) or too little cooling (thermal fuse in transistor module opens).

Have you checked the thermal fuse on old transistor module? If it's open, the transistor was not getting adequate cooling air flow. This might arise due to clogged/blocked inlet air filter, or might occur due to excess current flow through transistor

The transistor module thermal fuse can be replaced. It's a $2 part in US, but is a bit difficult to find.

good luck

 

As a follow up, the blower didn't stop working while I was using it (for about 5 minutes total time), but after I turned it off, and then restarted it hours later, it never came on. Also, I didn't install the transistor back in its slot, I just left it hanging. Could that contribute to the heating issue? I checked the filter, while it wasn't clean, it wasn't disgusting- and there was plenty of air coming out of the vents.


How can I check the thermal fuse in the old transistor module, and how can I determine if the blower motor is drawing too much current? I just took the transistor apart.


Would running the fan motor on a slower setting increase the heat, i.e. the transistor needs to reduce the voltage more and thereby heats up more?


Thanks,
Numaone