Rear AC blower fix

[Number_35]

The rear AC blower on our '09 Mazda 5 has never worked properly. This goes back at least five years when we bought the car. The 'rear AC' button illuminated on the dash, and the rear controls for fan speed seemed to work OK, but there was never more than the sound of an unhappy blower motor and a trickle of air.

We're just back from a western road trip, and I figured enough was enough. I had changed a very dirty cabin air filter before we left, to no avail.

I removed the centre console, and found the blower motor underneath. It seemed to work fine. Then I checked for a blockage in the ducting, but it seemed fine.

By trial and error I found that the blower seemed to work great, moving a lot of air, when the entire assembly was pulled away from the main HVAC plenum. Aha! If the blower is trying source air from a closed port, it won't put out much.

With the help of the FSM, I found that the 'rear vent actuator' was not operating - it had failed such that the port from the main plenum to the rear ducting was always closed. I removed the actuator and opened it up and found an operable motor and a bunch of plastic reduction gears. I'm guessing the replacement module is dealer-only and big bucks. I'll guess $200+.

My low-budget fix was to use a couple of cable ties to tie the port permanently open. As a result, there will always be a trickle of air ot the rear, even when it's not called for, ramping up considerably when called for.

A lot of work, but worth it I think.

Here are the bits I removed. (I'm also taking this opportunity to replace the two (broken) centre vents and a light in the HVAC controls , so a lot more came out than was required for just the rear air flow fix.)


Here's the rear blower and ducting, with the centre console removed:


Here's the troublesome 'rear vent actuator' in pieces:


Here's the low-budget fix - the 'flapper' is tied open with cable ties:

 

[eljefino]

You had me at zip-ties.

 

[Number_35]

Originally Posted By: eljefino

You had me at zip-ties.

They are the modern version of duct tape! I go through a lot of them.

 

[Number_35]

OK, so my low-budget fix didn't work that well - on the highway, there was a strong and steady stream of ambient-temperature air coming through the rear AC duct, regardless of whether the rear AC was on. This dilutes the AC in summer, and would be intolerably cold in the winter.

One (unacceptable) alternative would have been to remove the kick panel and remove the cable tie to close the intake flap every October, and to tie it back up every April. I can't imagine doing this twice a year.

So, fingers crossed, I reassembled the rear duct actuator and reinstalled it. It works perfectly now. (I don't know what the problem was, but later found a short video on YouTube of a fellow tapping the actuator to bring it back to life.) Glad to have the rear AC working, but wish I'd tackled this five years ago when we got the car. Oh well, we're in for some crazy hot weather, and will enjoy having it now.