2014 CX-9 front blower motor only works intermittently

[Akes]

Hello all, I’m new to this form, so thank you in advance for your advice. I’ve read several posts on what seem to be issues similar to mine. My front climate control fan will not come on reliably - only intermittently. The rear fan seems to work fine.

I’ve seen prior post about the fan, motor, relays, blower motor resistor, which is located near the cabin, air filter, and even replacing the fan motor itself. However, several prior posts did not include a final message as to what resolve the problem. Can anyone summarize how they were able to resolve this? Thanks again.

 

[Zoom49]

Hello all, I’m new to this form, so thank you in advance for your advice. I’ve read several posts on what seem to be issues similar to mine. My front climate control fan will not come on reliably - only intermittently. The rear fan seems to work fine.

I’ve seen prior post about the fan, motor, relays, blower motor resistor, which is located near the cabin, air filter, and even replacing the fan motor itself. However, several prior posts did not include a final message as to what resolve the problem. Can anyone summarize how they were able to resolve this? Thanks again.

You can test the components individually. When motor works do you have all speeds? If so resistor is good. When you jump power source directly to motor does it always run? If so motor is likely good. You can also replace the blower motor relay with the same type relay from another
circuit to see if that helps the issue.

 

[rowlands57]

The blower motor is not hard to access so a visual inspection may make it very apparent if there is damage to the motor. Have you checked the drains on the motor case? I have heard it is not uncommon for them to clog up and end up causing some damage to the blower motor.

Take a look and drop the motor and look for any signs of apparent damage and then test as mentioned above by Zoom49.

 

[Akes]

You can test the components individually. When motor works do you have all speeds? If so resistor is good. When you jump power source directly to motor does it always run? If so motor is likely good. You can also replace the blower motor relay with the same type relay from another
circuit to see if that helps the issue.

Thank you Zoom 49. I will check these points and come back with more information

 

[Akes]

The blower motor is not hard to access so a visual inspection may make it very apparent if there is damage to the motor. Have you checked the drains on the motor case? I have heard it is not uncommon for them to clog up and end up causing some damage to the blower motor.

Take a look and drop the motor and look for any signs of apparent damage and then test as mentioned above by Zoom49.

Thank you Rowlands57. My understanding is that when the motor does eventually come on, it seems to function normally, and so damage to the motor would seem unlikely (my thinking regarding possible damage is that the Motor would either work or it wouldn't, but I may be overlooking some scenarios here).

 

[youri]

Zoom49 eluded to the potential resistor as the problem. If that is the case it is really easy and cheap to fix. The symptom of a bad resistor is if only some of the speed work but not all. (For example, if full speed work but half speed doesn’t work then it is likely a bad resistor).

 

[Akes]

Zoom49 eluded to the potential resistor as the problem. If that is the case it is really easy and cheap to fix. The symptom of a bad resistor is if only some of the speed work but not all. (For example, if full speed work but half speed doesn’t work then it is likely a bad resistor).

Thank you youri. I appreciate your point, and seems most logical. However, I suppose it may also be possible that the resistor (which has multiple resistors with different resistances onboard) has a bad resistor at perhaps the lowest fan startup current which fools the motor control module into thinking that the fan is actually blowing when it isn't. Does that scenario make sense to you, or is my thinking faulty here?

 

[youri]

I am going to attempt a response but note that i have very limited understanding of how the CX-9 is setup and these resistors work. I am basing myself on the mazda 3 2010 that i own and had a similar issue.

I think in a bad resistor the signal just doesn’t make it through the resistor to the blower motor.

My understanding is: the resistor is a kind of an electronic card/sensor that sits in the air flow and measure the air flow. (In the mazda 3 it is right by the cabin air filter). When it goes bad it cannot measure the air flow and does not send the signal to the motor to blow at a certain speed. (It is dumber than that and is only sending voltage instead of signals i think but that is kind of its function).

But in a lot of car, when you set the blower motor to full speed, the circuit bypass the resistor (instead of measuring the airflow to set a certain speed it skips the resistor and it just goes full strength). So in a car with a bad resistor, lower speeds wouldn’t work but full speed would.

Anybody feel free to correct me if I got things wrong here.

 

[Akes]

Thank you so much for this detailed response. Makes sense - I'll check w/ my daughter (owner of the CX-9) to see if the blower works across all speeds or not. Stay tuned!

 

[PTguy]

Or the motor switch could be failing.

 

[Akes]

So my daughter reprints that when her fan does eventually come on, it only blows at highest setting, matching youri’s description of the symptoms of a bad fan resistor. I’ll replace it over the next week and come back to this forum with more feedback. Thanks again everyone.

 

[Zoom49]

But in a lot of car, when you set the blower motor to full speed, the circuit bypass the resistor (instead of measuring the airflow to set a certain speed it skips the resistor and it just goes full strength). So in a car with a bad resistor, lower speeds wouldn’t work but full speed would.
Youri has this right

 

[yrwei52]

Hello all, I’m new to this form, so thank you in advance for your advice. I’ve read several posts on what seem to be issues similar to mine. My front climate control fan will not come on reliably - only intermittently. The rear fan seems to work fine.

I’ve seen prior post about the fan, motor, relays, blower motor resistor, which is located near the cabin, air filter, and even replacing the fan motor itself. However, several prior posts did not include a final message as to what resolve the problem. Can anyone summarize how they were able to resolve this? Thanks again.

Here’s a typical schematic for the fan motor with resistors where their function is to change the fan motor speed. The more resistors connected in series will increase the resistance with the fan motor, hence reduces the motor speed. The direct connection skipping all resistors is for the highest fan speed. So if one of the resistors in the resistor pack blew, the current got cut, and the motor wouldn’t turn but only at the full speed without passing any resistors. The reason why the resistor pack is usually located in the air path that’s for better heat dissipation.

As for OP’s problem, it’s possible that the fan motor itself is failing by worn-out shaft and bearing due to high moisture environment which is common for the gen-1 CX-9. If the blower fan will not come on reliably, only intermittently at any speed, it can’t be the resistor pack. If the blower fan can only be started at the full speed immediately and consistently, but not on most or all lower speeds (depending which resistor blew), then the resistor pack could be the culprit.

 

[Akes]

Thank you yrwei52! This is very helpful. We ordered a new resistor and plan to replace (behind the glove compartment). Still waiting for delivery, but will report back when the new one is installed and we can test the blower function.