I've had this come up with my car, and having read this thread and confirmed that the actuator is not moving in the middle zone, I determined to fix it myself. Not a big deal.

I call up the local dealership Mazda parts department and ask for availability and price of the part. He tells me that he doesn't stock it, and that he has to order it from an outside supplier, not Mazda, and the part is remaned, that there is no core charge for my unit, and it all comes for the low, low price of ... $417.93. Well, well imagine my joy at discovering what a great deal my local service center was offering on a REMANUFACTURED part. I objected to the price, the part and the deal. He said that he would call the supplier check and get back to me.

I took that opportunity to do a little looking around myself. The part MSRPS new from Mazda for $289.55. It can be purchased on-line new for around $230 depending on provider. It can be purchased remanufactured for around $125 from Mazda with a 1 year warranty. I bought one from another Mazda dealer in my area.

Kid calls me back and tells me that he had misquoted the price. $417.93 is the price for the part new, and remaned it is $189.50. At this point I confirm we are talking about the control unit; the one with the knobs on it for the heat ... that thing! He tells me that that is what we are talking about. I then tell him that I have already bought it at another dealer and that MSRP - THE HIGHEST AMOUNT MAZDA WANTS HIM TO CHARGE is $289.55. He couldn't believe it.

So, just be careful when buying your parts to check the prices. You never know what somebody is going to tell you.

Good time for a bump. Mine just crapped out on me as well.

It's been acting strangely for the past few months. At first it would take several attempts to set the temperature control to the setting I wanted. This morning it went ahead and decided it was time to stick to cold air only, regardless of where I set the temperature controller.

Thanks for the tips everybody, I'll check it out when I get home.

My HCU was replaced under warranty for the same reason. It would only blow hot if I turned the knob really hard to the right.

My actuator has been doing the binary dance since I owned the car, and this summer I decided to unscrew the actuator arm and leave it fixed in the cool position... but I swear some hot air still makes it through, and it is pissing me off... I never use the A/C, and even here in hot as hell Tucson, I can get by with windows/sunroof...but it really pisses me off that I can feel the air outside seems cooler than the fresh air coming in the vents.... Is there anything I am missing as far as blocking heated air from getting into the cabin? Is there a fuse I can pull? Is there a stuck valve on the heater core?
I might just order the replacement control box, but I would like to know if there is another way to ensure no fresh air is getting heated... Any input welcomed...

-C

it wasn't the control knob for us. it was the heater core itself was clogged. I was able to make sure the control knob functioned properly by laying underneath on the driver's side and looking toward the center (under the dash). with someone moving the control knob for me while i was down there, I could tell the vents were opening and closing properly.

what we found out was that the inlet and outlet tubes on the heater core are on the same side and will let the water flow in and out without going through the heater core vanes. Consequently, flushing the system takes a long time because it is difficult to get the water to flow through the heater core vanes.

I had this same problem and I fixed it for $4

That is how much a new soldering iron and solder cost me

https://www.rx8club.com/showthread.p...light=heat+diy

that is all you need I promise it will fix your problem. Mine would shoot cold air only too and when I pulled out the HU I saw where the contact point for the knob had the solder disconnected so it didn't connect to the electric board.

Didn't notice the date on the previous posts way to revive a old thread for no reason Shadetree

Reply: I also have a 2004 rx8 but I do not have the stock radio. and my car does not blow hot or cold ac air. just the ambient temp outside. I and not sure what I should do, and really do not want to take it in to the shop to get it check out?

Did you check the connections on the controls to determine if the controls are the issue. See this search (run a Google search with ex8club.com heat er controls yields):

https://www.google.com/url?sa=t&rct=...5gFY0RC3AbyEZA

https://www.google.com/url?sa=t&rct=...slMWkYoX8xXD7w