2007 Toyota Corolla AC Blower Issues

Will the motor run if you plug it back into the harness?
Sounds like the harness length is very short but can you then maneuver the blower motor around and does it become intermittent?

No, the blower motor fan doesnā€™t turn at all at this point. This, too, is strange because I began thinking the wiring was the problem about two weeks ago when I removed the blower motor and plugged the power in with the motor just sitting in my hand. It actually ran at first, but if I moved it (and the wiring going to it) around, it would blow more slowly or stop entirely, which suggested the wiring to me. However, since then, I havenā€™t been able to get the blower fan to spin at all. That was actually the case with the original blower motor, too. When it stopped working, I just uninstalled and reinstalled it hoping that it was just a weird connection issue, and it started working again, but only for a day. When I replaced it with the current blower motor, everything was fine for about five months, and then the new one started acting up, not coming on some of the time until I smacked the glovebox or drove over a pothole.

Since I replaced it just two years ago, the ā€œnewā€ blower motor is under warranty, so the online store I bought it from is shipping a replacement. I hope that the issue is just the connector on the thing, as some have already suggested. Itā€™s been really annoying not to be able to isolate the problem.

So from your voltage testing you think the new motor is powered up ok, but it doesnā€™t turn? hmmm ā€¦ well, that pretty much means the motor itself is kaput, or that thereā€™s something mechanically preventing it from turning, like the cage that it spins is stuck for some reason. Does the cage (the fan) come with the motor when you buy it? Or are you using the existing fan and bolting the motor to it? What Iā€™d do in this situation is bench test the motor to see if it spins ok removed from the car when properly powered up. Youā€™ll have to come up with some kind of power supply. A car battery would do it. I have a computer power supply I removed from a computer a neighbor was throwing away which I use for that kind of test. If it doesnā€™t turn on the bench thereā€™s a chance there is something preventing the motor from turning once it is installed. That can cause the motor windings to burn out, ruining a new motor in just a few minutes of being powered up like that.

It takes two connections to power the motor. Itā€™s possible the ground connection is broken. You can only check this with the motor plugged in, check the voltage from chassis ground to both motor terminals. One should read 12 volts, the other zero.

Use your meter on resistance measurement mode and measure across connector terminals on blower motor. Should be relatively low resistance. Let us know reading you get.

Look at terminal ends of motor connector. Does it look like they are both same distance back of connector face? If one or both pushed back, will not make good contact. Do they look intact and also not spread open more than normal? Check to make sure your wiring harness connector pins are also fully extended and in good shape.

In the illustration I was able to access, the blower motor appears to be under the ductwork. The motor impeller will always be in the ductwork, ergo the motor will always be mounted on the ductwork.

From what you stated about the problem it does seem you have some sort of power connection problem. The testing you did with the voltmeter was good but if there is a connection problem before the point you did the testing at and had no load on the circuit when testing the meter reading will mislead you into thinking that there is no problem but there really is. Without any current flowing at the time the full voltage of the power supply will appear at the open point of the circuit. It gets down to Ohmā€™s Law, which I wonā€™t get into right now. Just be aware that when chasing a faulty power circuit it is best to have a load tied to the circuit and current flowing when checking for a problem. A bad connection will cause a voltage drop across the bad connection when current is flowing through it which robs the load of power. You could even use something like a brake light to act as a load if you donā€™t want to use the blower itself. With a load in place the meter will show how much voltage is actually getting to it that isnā€™t being dropped at the bad connection point.

If you havenā€™t replaced the blower relay yet you might checked the voltage there to see if the relay is causing the issue.

Well, I got the replacement blower motor in today and installed itā€“and I have air conditioning again! Iā€™m really hoping that the failure the original part and the first replacement was limited to issues with just those parts. If this second replacement stops working prematurely, would it be reasonable to guess that something might be shorting these blower motors out?

The most likely cause of a DC-blower motor failure is the cage gets stuck, or doesnā€™t turn freely, which stalls the motor and that burns the windings. When the motor is turning it is sort of acting as its own generator; i.e. generating some its electricity demand. This effect limits the amount of electricity from the battery. But when the motor stalls that no longer happens and a lot more current goes directly through the motor windings and burns them out.

Your blower is working on all speeds right? As expected? And you checked the cage area for any debris that might restrict it from turning feely? If so I think you are good to go, and just got unlucky on the first replacement part. Listen to how it sounds when running now, and if that sound changes, or if it seems to be blowing slower or not as forcefully, remove it and check for debris blocking the cage.

This AC blower motor issue is driving me bonkers. Summary:

  1. I replaced the original blower about 2 years ago when it stopped functioning. Prior to that, it would stop working intermittently but would resume functioning if I banged on the glovebox hard enough.

  2. The replacement blower started exhibiting the same issue as the original after only five months. I replaced the resistor, the fuse, and the relay just to cover the bases. The replacement stopped functioning entirely after about 1 year so I replaced it.

  3. The second replacement blower worked fine after installationā€“for about 3 months. It then started exhibiting similar symptoms as the original and the first replacement. It sometimes doesnā€™t start blowing, or it stops blowing after gradually slowing down in speed.

The only thing above the blower is the cabin air filter. I can remove the filter and manually spin the blower, so it doesnā€™t seem like there is an obstruction. However, Iā€™ll take it out and have a look to make sure. I did notice after installing this latest replacement that it emitted a barely audible high-pitched whine, but I honestly donā€™t know that the previous blowers didnā€™t do the same. Thoughts?

Iā€™d take two wires and somehow connect them to the two conections of the motor. Run those wires to somewhere in the passenger compartment and put a voltmeter across them. Now you can monitor the voltage that the motor sees and when it stops see if the voltage drops to zero (which I bet it will). Then you will know that the problem is not the motor but in the wiring somewhere.

It seems like it has to be the wiring. I disconnected the blower motor and removed it to check for obstructions (none), then reconnected it, no change. I checked the voltage coming from the wires going to the blower motor and couldnā€™t get anything. The wires are pretty short and the connectors are small, so I kept trying to get a reading to make sure I just wasnā€™t missing the metal of the connectors. For some reason, I thought to check the relay. I swapped it with the horn relay for shits and gigglesā€“and then I was able to get a reading of just over 12 V from the voltmeter. I reconnected the blower motor, and initially nothing happened, but soon the fan on it began to spin. However, as I moved it around, it spun less and less, until it finally stopped spinning completely. I swapped the relays again, and I was still able to get over 12 V coming from the wires but could not get the blower motor fan to spin at all. In other words, the problem is horribly inconsistent.

The blower motor uses considerable current and that can heat up the connectors and over-time result in a bad connection. Then youā€™d have 12 volt coming out of the relay ok, but by the time it gets to the motor, not much. Usually that kind of connection problem would happen somewhere between the relay and the motor. Thereā€™s probably a connector near the relay, and another near the motor. It is sometime difficult to probe the voltage without disconnecting the connector which masks the problem. Iā€™ve used a sharp pin like come with a dress shirt to poke through the insulation of the wire, allowing me to probe the circuit without disconnecting anything. If you measure 12 volts on one side of the motor using the pin method, and something near 0 volts on the other (you have to probe the ground side wire too, from it to chassis ground), then if the motor isnā€™t turning, the motor is faulty or the thing it turns isnā€™t moving freely.

Upon starting the car today, the blower motor spun normally. I drove for about 10 minutes and the speed of the blower gradually decreased until it wasnā€™t blowing at all. So frustrating.

Does the resistor diminish the voltage sent to the blower motor depending on the position of the speed selector? If so, does that mean that the blower motor will spin at a voltage lower than 12 V? If thatā€™s the case, would it be possible to bypass the wiring to the car battery and connect the blower motor to a smaller battery? I realize that sounds silly, but I live in Arizona, so Iā€™m desperate for a workaround until I have time to do more troubleshooting.

On my older Corolla the blower speed is controlled by the amount of resistance in series between the blower and the battery. Thereā€™s a set of resistors and the speed switch just selects which ones to insert in the circuit. Higher resistance, lower speed. Lower resistance, higher speed. Not sure how it is done on a 2007 as new vehicles tend to use an electronic control module rather than resistors.

I presume you mean a smaller resistor, so the motor turns fast all the time. Yes, thatā€™s possible, but it would have to be done safely so it doesnā€™t start a fire, or damage other electronic components in the car. If you decide to try that method, make sure the person who does the wiring changes has the necessary training and experience in automotive electrics. I think youā€™d be better off spending your $$$ on hiring a mechanic to just fix the problem in the Toyota recommended way.

A couple of ideas, first the longer the blower is on, the hotter it gets, and the hotter the wiring feeding it gets. That could explain why it starts out blowing fast at first, then slows down. Either the motor is defective, or thereā€™s a high resistance connection that heats ups and gets even higher resistance as the motor is operating. Another possibility, when you spin the motor/cage by hand it spins freely. But there could be an obstruction somewhere that doesnā€™t hit the blower cage until the motor starts spinning fast. The centrifugal force on the cage as it spins will cause it to expand slightly in diameter. Likewise for the spinning armature inside the motor. And if your Corolla uses an electronics module to control the speed, that could be faulty, and have nothing to do with the motor or the wiring.

So the temperature issue seems like a real possibility. This problem has always recurred or gotten worse during summer. If thereā€™s a connection thatā€™s heating up, is it possible that the external temperature just accelerates that process?

The 2007 model does have a resistorā€“but it also has an engine control module. I donā€™t know if the engine control module does anything with the AC, though. Iā€™m guessing that it doesnā€™t since I had to disconnect the ECM to replace the blower motor and tested the replacement before reconnecting the ECM.

Anyway, it sounds like Iā€™ll have to bite the bullet and have a professional look at it. If itā€™s the wiring, I assume Iā€™m looking at a cost of at least a few hundred dollars. This car is too old to be pouring money into, but I do need it to last until Iā€™m done with school, and I canā€™t see enduring the Arizona heat without AC.

Have you tried the pin method to pierce & probe the wires and measure the voltage right at the motor when this problem is occurring?

It looks like thereā€™s no electronic control of the blower motor on your Corolla. Just the panel switch to turn it on and set the speed, a relay, and the resistor network. The ECM isnā€™t involved. There is a fuse in the circuit called the heater fuse, might be a good idea to take a look at that for signs of corrosion or burned terminals. Below is the nominal value for the resistors

pins resistance

1-2 1.5 ohm
1-3 0.5 ohm
1-4 3.25 ohm

I would look at the speed selector switch. It is quite possible that one of the resistors is failing. I am not sure whether yours has a 3-selector switch or an infinity switch. Either way, it can be the source of your problem.

I havenā€™t had time to try the pin method, but I will. Iā€™ll also check the heater fuse.

In the meantime, hereā€™s a crazy idea: The 12 V socket for accessories (cell phone charger adapter, etc.) works fine. If an adapter can be fashioned so that the wires coming from it connect directly to the blower motor, wouldnā€™t that work by bypassing the problem connection? Weird solution, sure, but if it works, Iā€™ll do it until I can find the problem wiring.

I drove for about 10 minutes and the speed of the blower gradually decreased until it wasnā€™t blowing at all. So frustrating.

Bad blower motor my guess. If you are ambitious enough to clean and lube the bearings go for it, otherwise replace it, my wag