DIY: No Heat? Repair the Heater Control
 

No heat and only cooling, or only heat and no cooling, or erratic temperature control?

The temperature control knob seems to have quite a bit of issues for early RX8 owners where the system will cool only, and not provide heat despite the position of the control knob. This can also work in the opposite way, only heating and no cooling. After living with it for a season, I finally pulled the heater control unit out and repaired the circuit board. It was simple to repair and because I was going to have to pull the unit out anyway to replace it, it was not much extra work. The replacement unit (part FE01-61-190) retails for $350, some vendors on this site sell it for $240ish, and I hear there are some that sell used parts for $125ish. It is definitely covered under warranty for those lucky enough to be under warranty.
If you do not have heat, or only have heat, IMHO it is most likey the AC/heater control unit. This is the part which has the AC/heat control buttons and knobs.

Easy Diagnosis:
The easiest way to verify this is to turn on the radio, press and hold the power on/off button and press and hold the scan-up button for a second (full second). The word "A/C TEMP" should appear on the left of the display and a number from 0 to 16 on the right. I suspect yours will have the number 0 (or 16 if heating only problem) displayed no matter where you turn the temperature control knob. If this is the case you could turn the temp. knob to full heat and see if it goes to 16 after pushing down or to the right on the knob.
In a working system, the number moves evenly in increments of 1, from 0 to 16 as you turn the temperature knob.

Easy Fix:
I was able to take mine out and solder 3 loose connections to fix it.

The beginning steps are the same as for any radio removal procedure. Instead of reinventing the wheel I would like to direct anyone to John Masone’s excellent DIY for radio removal at this DIY:
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-radio-removal-add-aux-input-36001/
or directly linked here:
http://www.whatsmyip.org/ipodrx8/
The procedure is basically the same until page 7, second frame. Here is the modified step at that phase:
http://i483.photobucket.com/albums/rr191/waxer/16-1.jpg
Removal of Heater Control Unit

I did not take pictures of the next step which is basically removing the cover on the temperature knob side of the control which requires a small screwdriver to three plastic clips on the perimeter of the cover. This will be evident when you get it in front of you. I stripped the circuit board down further than you may need to because I was also repairing cracked defrost (windshield and rear) buttons with superglue.

Then re-solder the 3 joints indicated in the next photos. A little bit of heat and just a little extra solder and they should be good to go.

http://i483.photobucket.com/albums/r...r/IMG_5235.jpg
Front of Heater Control Circuit Board
http://i483.photobucket.com/albums/r...r/IMG_5236.jpg
Front of Temperature Control Knob (3 connections noted)
http://i483.photobucket.com/albums/r...r/IMG_5237.jpg
Back of Heater Control Circuit Board
http://i483.photobucket.com/albums/r...r/IMG_5242.jpg
Back of Heater Control Knob
http://i483.photobucket.com/albums/r...r/IMG_5241.jpg
3 Bad Solder Joints (Note cracks) Prior to Re-soldering

I did the power-button/up scan combination to get the head unit to display the dial position and it now travels even increments from 0 to 16, instead of jumping from 0 to 16 when pushed like before. And the temperature control works perfectly.

Good luck.

Excellent stuff. Hope this gets stickied.

you might want to take some bigger picture :)

Anyway, excellent post !

This is fantastic. I wish I knew it was this simple before I replaced my bad one.

Oh well, I guess I'll get the soldering iron out and repair the old one anyways, its always good to have spare parts.

Ahhh i was waiting for this.
it was getting annoying trying to find the sweet spot where heat would work.

I just got done trying this, and it worked perfectly. The most annoying part for me was finding (yes finding !?!) the bolt to undo the radio.

After looking around under the steering column for half an hour or so and not quite being able to get my head in the right spot to see the bolt, I finally removed the metal part that goes across the bottom of the column (you can see it in the bottom picture on page 4 in the radio removal DIY). It is held on with 4 screws. With that out of the way, I was able to see the bolt and get at it much easier.

Also, the part about being careful about not dropping the bolt is important. I was being very careful right up until I dropped it into a bottomless pit.

Continuation of Wingnut's DIY
 

I just got done doing this today. Worked EXCELLENTLY. I'm posting up some additional tips and instructions to make this even easier.

Tip: When unscrewing the bolt behind the dash, make sure to put some sort of sticky, adhesive substance on your ratchet socket. I went ahead and put some electrical tape on mine, sticky side up. If you don't do this, your bolt will likely drop somewhere behind the carpet and be lost forever. Also, when putting the bolt back I recommend taping its rim to the ratchet socket. That way it will stick to the socket until it is locked in tight enough and you can just pull the socket off, with nothing falling.

Ok, from this point in Masone's guide til the beginning of Wingnut's DIY you should have no problem following the instructions...

Now, once you get the first picture posted by Wingnut, his last step mentions to unscrew 2 screws to get out the ac unit. It is actually 6 screws, two on upper unit, two on lower, and two below the unit, although you will likely figure this out just thought I'd put it in there for sake of completeness.

Anyway, after you have pulled out the unit, you will arrive at my first photo (attached below). Unclip the pieces using a small flathead screwdriver at the three locations indicated by the red circles. Also, loosen the wire bundle on the right from its hooks so that it can slide into the case later on (when pulling out the circuit board).

After this (as indicated in my second photo), flip the unit around and unscrew the center mode control by unscrewing the screws at the 4 red circles. Next, bend out the side portions (at the yellow circles) a bit to unlock the board from the plastic case. I recommend unmounting the left side first. When doing the right side, use a small flathead screwdriver to pry the wirebundle (indicated in my third photo) from its socket on the board. This allows the board to come out enough so that you can solder the joints.

Lastly, you should have access to the necessary joints (indicated in fourth photo) and you can resume following Wingnut's great DIY. The soldering was very easy - as Wingnut mentions - and I didn't have to remove the two wire bundles plugged into the board in picture 4, as I was able to get it to bend out far enough to easily work on it.



I hope this helps someone out! After you do it, you too should be: :git:

Good stuff.. I was hoping someone else would figure this out for me :lol:

Thanks!

Thanks Wingnut. I thought I was screwed out of a few hundred dollars until I did a search. Took about half a day including having to pick up a soldering iron. Couldn've been simpler. Hopefully Mazda will make this a recallable issue. Sounds like this issue is showing that the circuit board has some defects.

have not had the problem with my car, but did the same on a dell laptop..

great job!!!

beers :beer:

YESS you are my hero now. Works fine thus far! However, a question to those whoi did it.... where does this thingie go? lol It was below the ash tray...
https://img266.imageshack.us/img266/3764/thingxx4.jpg

I don't remember seeing that piece anywhere, hmm. My guess would be it belongs to the ashtray door hinge somehow...

Oooh I had lots of fun with that piece at one point. You will notice your ashtray door now swings freely and doesnt have the "snap" to it.

That spring goes in the ashtray piece, on the back. I'll try to snap a picture when I do this fix...

thank you very much. i'm going to do this next free saturday i have. probably next saturday. i'm under warranty but if i go to the dealer i'll likely lose my warranty for various things, so i'd rather just fix it myself.

Please do. I figured it went somewhere on the back to hold it and all, but could not figure out where exactly to put it.

Dear wingnut, I heart u

memebers such as yourself are what makes this club worthwhile

cheers!

Wingnut - Thanks! Great instructions, links and pictures. Took about an hour an a half and saved $$$. Kudos!

IKoRTy - That is from the ashtray hinge. Mine came off as well and that side of the hinge decided to disintigrate. A well placed screw fixed the problem for me. It is a little harder to open/close now, but it beats buying a new one when I never use the dang thing.

well great now i have to take it off again and try to figure out where the darn thing goes haha.
does it stick somewhere in the back? or what.

It goes on the back (left IIRC) ... Look for two little holes where the flat ends of the spring can go. One hole on the lid, one on the base.

I should be doing this fix over the weekend so I will snap a pic then

Hey CnnmnSchnpps, when during the weekend do you think you're gonna be doing this? I'm probably doing mine over the weekend as well. Maybe We could have a "Fix your heater" party with a bunch of the guys from the club

Looks like I have to do my wife's car over this weekend. I think she was waiting for me to experiment with my car before she trusted me with her's. Although her's is a little different as the temp setting keeps changing arbitrarily. I am hoping it is the same fix. I am up for the virtual party! Anyone want to come over and take care of that little bolt in the back for me??

Big thanks to you Wingnut. I did the fix and everything works perfectly now! Thanks for taking time to figure this out and document it so well. I'm ready for winter now. (c:

Devin

Big thanks for your work you did, you beat me to making a DIY. You did a great job. Saved me 300.00 bucks

Whoops, sorry mate, missed your message. Did this today.

Wingnut - Very nice DIY! Thanks a ton. It only took like an hour to do this fix. My soldering ain't pretty but it will do the job :eyetwitch

Someone had previously attempted the radio removal on my car, since I had no retaining bolt, and the main harness connector on the back of the radio was mangled beyond recognition, so much so that I could not actually remove the radio...



As promised, here is where this part goes (picture taken with the ashtray lid closed) - on the right side of the ashtray assy. It's a real PITA to get back on - have fun :rant:

-D

I want to thank everyone that posted tips on this...
Thank you, thank you, thank you!

I just finished doing my 2004 and the heat and cooling control now works like it is suppose to. Mine started acting up a little bit a year ago, but got real bad a few months ago. I had a dealer look at it a couple weeks ago, and they quoted me $800 to fix it and I believe they misdiagnoised the problem and were going to replace the A/C amplifier under the drivers side dash! Lucky for me they didn't have the parts, so I left with no bill.

The easy and sure diagnois with the "hold ON/OFF button and push SCAN up" gave me confidence this was the problem. And it also confirmed the fix before I even started up the car, just turned the key on and checked it.

The only bad part was my ash tray spring did pop out, and I wasted a half hour trying to put it back in. Then I noticed one of the holes was broken in half (not on the ash tray door, on the ash tray body. Is this caused when the ash tray is removed with the door open? Would it have helped to close the door when removing it? I don't know, but I am happy the heat/cool works again. I was able to super glue the broken bit, and then put 2-part epoxy over it for more strength. The ash tray snaps open/closed correctly now, I'll see for how long.

Took 2 hours, including my wasted 1/2 hour with the ash tray spring. Somebody more familiar with the electrical connectors could do it faster. It did go back together easier than taking it apart.


Thanks to all.