Hello, I have a 2007 Acura TL 3.2. When I was driving a couple days ago, I noticed my window wasn’t defrosting because there was no heat blowing out, started to mess with the settings and the fan eventually started working. The next day, it did it again and I didn’t mess with any climate control settings but it started blowing heat by itself about 5 minutes into the drive. What could cause this intermittent power of the blower motor?

 

Is it set to Auto? If so, you know that blower motor will not operate if cold outside, and engine didn't warmed up yet, right?

 

If not what peter mentioned, the most likely culprit will the blower motor power transistor failing.

 

Not set to auto, any good guides/videos on the blower motor transistor?

 

Pull the lower dash cover, right there in view, remove 2-3 screws, unclip harness, swap parts, reverse steps to re-assemble. I don't remember if I found a video on YouTube or a DIY thread in here.....but it was probably a 10-15 minute job.

 

Update:It seems to not be working at all after a 20 minute drive, could this still be the transistor? I let the car warm and and it defrosted the windows but there is currently no air moving through the vents after roughly 40 minutes of it being started

 

It "could" be many things. The most likely is the transistor failed. If the blower motor doesn't work at all, sticks on HIGH, or is intermittent....it "could" be the transistor. It is generally the easiest and cheapest option to replace. It could be a failed motor as well...but less likely. It could be some other electrical issue...but less likely.

If you search the forums, for "blower motor transistor" or "blower motor resistor" you will probably find many threads on this in the past. The majority of them were the transistor. Mine was wonky for 2 months leading up to when it just stopped working.

 

Hi folks. Just for the ease of trying to find the right part, the part in question is called a "Thermistor", not a transistor. Some parts stores have it labeled as a "resistor" which more closely resembles the function. I have a 06 3.2 TL in which I replaced the thermistor at least twice and replaced a blower motor once. It is still acting finicky. One day when my wife came home and told me the fan wasn't working, I reached down and wiggled the electrical connector at the fan and it started to work.

As mentioned previously, the fan is under the glove box to the right. The thermisor is a suspect, but before you replace it, when the fan doesn't work, reach down and tug and push on the connector to the blower motor and see if that does anything. My wife hasn't had a problem now in 3 months since I did that. Maybe it will work, maybe it wont, but if it does, it's free...

 

Pretty sure it actually is a transistor. A thermistor is usually more for temperature detection/control, not for adjusting the amount of power being delivered to a circuit.

 

Just like Jackass wrote:



And this is taken right from climate control diagram:


Transistor is like a switch. Kinda like a relay, just it's solid state, not mechanical. It turns ON and OFF very quickly (probably above 100,000 times a second) and that's how it regulates amount of energy going into the blower motor, therefore regulating the speed.

Some stores label it as resistor, simply because in some systems there is a actual resistor. Just not the case of our cars. Most often you can find resistor when car has simple 0-1-2-3-4 speed regulation.




And coming back to the thread - in this case I would back-probe the blower motor plug, and connect it to some lightbulb... let's say 15W 12V. If lightbulb is bright and blower motor doesn't turn, and you can change brightness by changing the fan speed, then replace blower motor. If you still not sure, then disconnect the motor and connect stronger light bulb (35W? 55W?) and recheck.
If lightbulb doesn't lit and motor doesn't run, then most likely transistor. In case of our cars I could try putting an oscilloscope at pin #4 of the transistor to check if it receives command signal from the computer, and if blower motor has good power. Or for example remove transistor and jump pin #1 and #3 and check if blower will run at full speed without problems.

One more thing - there is a blower motor relay in the under-hood relay box. Swap it with some other same looking one - just not with something important.

 

Well then, I stand corrected. Maybe... Picture direct from RockAuto...

 

Calling it a resistor isn't a huge issue....that is not the part we are trying to correct. Older cars used resistor packs to get the multi-speeds. In more modern cars with more than just a few speeds, a transistor takes this function to give the 6+ speeds most cars have these days. Many people, myself included, still call it the blower motor resistor by default.

But a thermistor is a completely different beast. Technically the interior temp sensor located below the steering wheel is more than likely a thermistor.

 

I was just trying to help people find the part. I haven't encountered it being called a transistor at a part store.