The HVAC fan seems to have lost high speed on our '13. Searching didn't yield any any reference to the problem, diagnostic procedures or likely fixes. Can any of you help, or point me in the right direction?

Mark

 

You may need a new fan, or the switch itself or the relay may have failed. Does the fan sound normal at other speeds?
Have you tried running the system on automatic? On mine, on a hot day with the climate control on auto it will run the fan on the highest speed.
When was the cabin filter changed last?

 

Thanks man. I checked the cabin filter at the last oil change in April, and it was clean, but I'll have another look today. We originally noticed the issue on Auto, which is the only mode we ever use. Switching to manual and using the fan controls to engage max speed moves the bar graph to max, but the fan speed only advances so far. I *think* the other fan speeds are normal, but they could be a little slower than normal. I don't drive this car much, and can't say for sure.

Is the blower motor control module built into the blower, or always included with it? I found blowers on Rockauto, and one of them says it includes the blower control module. I'm thinking of replacing them both, but am not sure if they are separate parts.

Mark

 

Seems odd to me that you have full range of fan but that everything is just a notch lower than you expect. My line of troubleshooting would be as follows
- have you opened up any vents that are normally closed, particularly the ones for the rear seat
- is there air leaking by into a vent position where it isn't supposed to. Like if you command air to go thru the dash vents only, might some actually be coming out the defroster or footwells as well?
- does toggling recirculation make a difference?
- if the cabin air filter is good, could there maybe be blockage at the air intakes by the wipers? Or maybe even inside those intakes- does the fan speed appear to change as you drive, even if it is manually set to be at one speed?
- does the amount of air and the temperature of air seem to change with the amount of time since you started driving, or perhaps change with the speed that you're driving?

 

Back in the day of rotating control ***** for fan speed, when some of the fan speeds stopped working that meant you needed to change the blower motor resistor pack. Not sure if the electronic controls still rely on the same kind of setup, but that would be something I would investigate.

 

And another little piece of me dies...

I must have been remembering my jeep's cabin air filter when I mentioned that it looked good this spring, as the one in the RX was filthier than I've ever seen one get. A new filter solved the problem.

Thanks guys!!

Mark

 

Well done. Clogged filters cause all sorts of problems, and can drastically shorten the lifespan of any HVAC system.

 

Great. Happy ending. I was worried it was going to be the blower motor. Lexus had to replace that in my RX for the previous owner.
I'm surprised though that the bad cabin air filter didn't make it smell in the car.