Heater blows only cold air
 

My fiance has an '04 RX8 (out of warranty) and the heater blows only cold air. Took it in to the local dealer in Seaside, CA, and was told it needs a new A/C amplifier which had to be ordered and prepaid to the tune of over $700. I've searched the internet and haven't found a single reference to a heater not functioning in an RX8. Has anyone here had any experience with such an issue?

Obviously, the car generates plenty of heat, but the necessary vents apparently aren't opening to allow the heat to get through. Would the A/C amplifier control that?

Thanks for any suggestions!

Steve

could be, but not sure. i guess you guys drive the car quite a bit? check with mazdamaniac here on the forum about getting the appropriate info out of the service manual, anc check mazmart in the vendor forum and see how much he can get you an a/c amplifier for.

Here is a tread with some info about heater problems, we had a repair on ours.

https://www.rx8club.com/showthread.p...7&page=3&pp=15

There are also a number of HVAC TSB's out there: http://www.finishlineperformance.com...ins_index.html

If yours falls under one of the TSB's you might get it done for free even if out of warranty.

make sure the green light on the A/C button is not lit up.

parts were ordered for mine.
when using the heater, try forcing the knob a little more clockwise. does it blow hot air?

The A/C button is not lit up. I checked out the thread suggested by ULLLOSE and found the post which I've cut and pasted below. Can anyone tell me what the A/C amplifier actually does?


Quote:
Originally Posted by fray
My 8 had this problem, turned out to be a faulty heater control unit. A few other people have had the issue as well.

From my issue (and another persons issue)

CUSTOMER STATES WHEN ADJUSTING THE AIR MIXTURE ONLY SWITCHES TO BOTH EXTREMES-SOP HERE HEATER CONTROL INTERNAL FAULT IN CONTROL HEAD.
REPLACE HEATER CONTROL HEAD.
U0207ARX .6 61/9W

To see if it's the same problem, find the air-mix actuator on the drivers side center console.. basically look at the center tunnel area near the gas pedal but "up" a bit....

with the car running (and the heater fan on).. move the temp knob. The air mix actuator should move following any change you make to the temp. In this particular fault. The actuator will go all the way cold.. and all the way hot.. in the middle it MIGHT jitter a bit.. but only does extremes. (And the dealer diagnostic procedures tell them to check the extremes.. but don't have rules for checking the intermediate range.) So you pretty much have to show them the actuator isn't working right to get it diagnosed.


My fiance's '04 RX8 went into the dealership last week because she couldn't get her heater to work at all. The repair order states:

CUSTOMER STATES HEATER NOT WORKING, COLD AIR ONLY
TEST TESTING/DIAGNOSIS $92.00
SOP WE HAVE SPECIAL ORDERED THE NECESSARY PARTS FOR THIS REPAIR
1 FE04-61-540 AMP.,CONTROL $605.00
DIAGNOSED A/COND AMP FAILURE, ORDERED PART. LABOR TO INSTALL WHEN PART ARRIVES $92.00

Can anyone tell me what the A/C amplifier does and how it would affect the heater?

After they charged her in advance for the A/C amplifier which hasn't arrived yet, I tried turning the temperature nob all the way to off and back to full heat and, voila, heat came through the vents. I then crawled under the dash and looked at the air-mix actuator while rotating the temperature knob and indeed it only does extremes. Sometimes I have to rotate the knob back and forth a few times before the actuator moves and the heater begins to flow. Rotating the knob toward cool in any increment, though, always instantly results in a change from hot to cold air.

This seems to me like the same problem fray is talking about. What I'm wondering, though, is why the dealer told my fiance she needs a new A/C amplifier (which they made her pay for it in full up front before ordering it).

This website is great! I wish I had found it before the car was taken in to the dealer.


Thanks for any help/suggestions.

Steve

--------------------------------------------------------------------------------

Thanks for the info. It does blow hot hair when, and only when, the knob is all the way to the right. It often requires rotating the knob back and forth to the extremes before the heat flows.

Do you know what parts were ordered for yours?

Mine had the same problem. Try pushing the power button and up scan button at the same time on your CD deck. It should bring up the word AC and a #. If the number is 0 no matter what poistion your hot/cold knob is than its a simple problem that should be fixed under warranty.

Thanks, I'll try that tonight. Unfortunately, the car is out of warranty so nothing seems "simple!"

i'll look into it. I had a bunch of stuff ordered for my car and i'm dropping it off tomorrow so i'll get a list of what they ordered tomorrow.

Had the same thing happen to my 04 last year shortly before winter time. before it finally broke fully it would constantly switch between hot and cold regardless of any knob input. Then it finally just went to blowing cold air all the time.

Tried the little thing above of reseting it with no results. The dealer replaced the amplifier under warrenty and since then have not had any issues. They never truely knew why it was behalfing that way though...

Thanks, everyone, for the information.
It's unfortunate that she's driven the car 63K miles so nothing is under warranty. Loves the car though!

The good news is that the heater is working so long as the temperature control dial isn't moved and the dealer says they will refund in full without any hassles the $605 + tax which was prepaid for the A/C amplifier they ordered.

If it turns out that it really does need the A/C amplifier to open and control the flow, I'm pretty sure I can disconnect the rod which controls the air-mix actuator and manually set it so the heat flows in the winter, then close it for the summer. Having a temperature control knob is convenient, but I don't think it's worth $750 (inc. tax & labor).

I had a problem like the first one (not weak ac problem)

A few times in the past couple weeks when I want the vents to blow in hot air (as I often do at night) but the air coming through was still cold. Yes the ac was off and yes the dial was all the way in the red. Turning the fan on would only blow more cold air and it would take a few minutes of playing with ac button/dials up and down for it to finally redirect the heat from the engine through the vents. I hope the problem is not developing to be greater because it is very hard to recreate thus hard to get repaired under warranty.

This is after the car has been warm and the vents open switched/heat selected. Anyone have any idea of the problem or just malfunction/bad luck. I have eliminated user error because it has happened more than once and I often use the engine heat/vent combo.

Any ideas?

Heater Control Unit
 

I've had that same problem for a while now.

It starts with the hvac just blowing cold air, good in summer, bad in winter. Then, if you move the temp control knob, sometimes you have to move it multiple time back and forth, it'll switch to all hot. Good in winter, bad in summer. Every once in a while it'll just change on its own. There is no inbetween, just hot-cold.

It was diagnosed as the heater control unit. The little knobs (temp control-fan) are attached to the unit. It plugs into the center console that has the radio and such attached to it. You can buy it new for about $250.00 from Online Mazda Parts, or call Mazmart and get one used for about $125-150, I don't remember. I just received my new used one from Paul. I plan on installing it tonight or tomorrow night. I'll let you all know if it fixed it.

Look here also ---> SEARCH :)
Cel

Just got the heater control unit in --- put in a CD changer also :ylsuper: --- and it works like a charm...

Cel

It sounds like the same problem we were having. Read the quote from fray which is several messages up in blue. You can see the actuator lever move to control the flow of warm air. If it only changes when you move the knob all the way to the right, then you can show that to the dealer to prove you have a problem while you're still under warranty. Good luck!

Cel,

Glad that worked out for you. I'm guessing that my fiance's car probably DOES have a bad A/C amplifier, but also a bad heater control unit. How much of a job was it to install?

What? The heater core is after the A/C, so this doesn't make any sense at all. In fact, the BEST way to defrost a car is with the A/C on and the heater at full hot. This blows hot, dry air on the windshield, raising the dew point and pulling the moisture off. In fact, when running in the defrost mode, the RX-8 forces the A/C compressor to be on...

Actually, this brings me to another point. Does anyone know how to disable the automatically-on A/C when in defrost mode or floor only mode? I don't always want the A/C on when I'm using those settings.

~ Matt

I'd try the Heater Control Unit first. The amplifier being bad just doesn't make sense. Those were problematic in summer when people were complaining of alternating hot and cold air comming from the ac when it was on, or weak ac.

Changing the Heater Control Unit was pretty easy. Here is a link to the website that was most helpful to me. It took about an hour or so. The two hardest parts were finding the "Hidden" bolt, because it is hidden and impossible to find visually, and getting the clip off of the fan control knob. Other than that it was very simple. I'd say that someone with just OK mechanical skills/knowledge could do this easily.

You'll need a Phillips screw driver, a little Flat Head screw driver (like the ones that come in the glasses repair kits), a 10MM socket and wrench with about a 6" extension. I had to use 2-3" extensions to get the bolt.

Let me know if you have any questions.

BTW MAZMART Rocks. I had to get a drivers side visor, and a heater control unit, and got a CD changer. Combined it was cheaper from Paul than a new heater control and visor. I also got everything in 2 days.

Cel

yep, tried it today when I got home before coming in and thats the problem. Won't even stay on hot when all the way to the right, just goes back to 0 (if you kind of force it a tad bit it will go to 16 but right when you let go goes back to 0) Still under warranty and will be for another 7 years/90k mi :)

My heater seems to be on the fritz too. For one, it takes awhile to get hot, more so than last year but this winter has been colder and I'm parking in a driveway vs a garage. But worse is once it gets toasty I try to turn it down a bit and it seems to do nothing at like 9 then 8 then all of a sudden at 7 it goes ice colds (keep in mind 7, 6 are clearly in the Red on the dial with 5 sort of being the divider). So then I go to bump it back up and it stays ice cold unless I turn it all the way to 10 (max heat). Then it gets hot again. Repeat. Try to turn it down a bit... ICE cold... turn it up incrementally and nothing until I get to 10. VERY frustrating.

This sound like the same problem with the actuator lever doesn't it? I'll have to try the test to see it move. I'm 6'4" and a big guy and no access to a garage. Should be interesting. ;)

Justarius

P.S. Is replacing the heater unit the same repair for the messed up actuator lever? I've seen mention of a bunch of people having the heater control unit replaced under warranty.

stevej119,

Someone may have already mentioned this but if it turns out it IS the A/C Amplifier there is a Service Bulletin out for replacing it. Here's a copy:
http://www.finishlineperformance.com...02-04-1338.pdf
In which case you should get it for free. Even if she's out of warranty, those bulletins are for known manufacturers defects right?

Edit: at the bottom of that bulletin it says for customers under warranty. Still, if it were me and there's a known problem that didn't surface until just after I was out of warranty I'd make a big stink.

But from the sounds of it your problem is the actuator just like mine. In this thread:
https://www.rx8club.com/showthread.p...=1#post1733755
Rasper says "You can buy it [HCU] new for about $250.00 from Online Mazda Parts, or call Mazmart and get one used for about $125-150, I don't remember".

$700 may not be worth having a working dial but $150 would IMO. And since he and I are from Canada, that's probably $150 CAD which is like $125 for you! Valentine's Day gift? :wink2:

Justarius

Really? I looked up and down that site and couldn't find any mention of HVAC bulletins. There's 1 about AC Amplifier and a couple about temp control knobs. Maybe it/they were taken down?

:uhh:

AC condenser protector
temp control dial-hvac temp/fan dial availability
AC temp fluctuation/lacks cooling

I would say that is a number, more than one, of TSB's that relate to the HVAC system. :dunno:

What the original thread starter problem was that the knob , actually the whole HVAC control dial was broken. the pin inside was loose(or broken) so when you turn it, if you're lucky the contact might be able to touch it and heat will come out.

I have mine replaced under warranty. but this part its something that you can change it yourself.