AC Magnetic Clutch Kills Idle
 

Here is one for both the AC thread searches and the Idle thread searches:

Air conditioner's magnetic clutch on my 03 build MT went bad on me, had to have the AC compressor replaced. Tech at my dealership (Mark at Werner Mazda in ManchVegas NH) had a bitch of a time getting the old compressor off - bolts seized - had to hit them with a torch (but I digress...).

New AC compressor is now installed and car is back home. Started it up today and noticed that I was suffering from the well known erratic idle syndrome. With fully warmed up engine the idle would periodically drop to almost nil, or the engine would stall, on a cycle that repeated about every 30 seconds +/- (I wasn't checking with a stop watch). Pop the hood to check it out. Discovered that every time the magnetic clutch engaged to cycle the new AC compressor, the engine would stumble. Once the clutch relaesed, the engine would surge to recovery, actually jumping to about 1200 RPMs, before settling back to around 800 RPMs.

Next time the AC compressor cycled on, same scenario. And so on, and so on...

The air conditioner was not actually turned on at the dashboard in the cabin, this was just the standard AC cycle the RX8 goes through even when it is not in use.

Anybody seen this before? Any fixes other than the new AC compressor may be a little "stiffer" than the old one at the moment and hence is putting too much drag on the motor when it engages to cycle?

Check the HVAC controls and wiring.

Unless you turn defrost on, the clutch shouldn't engage at all.

EVEN with A/C on, the compressor should not drag your engine's RPM up/down that much. you might have some other problems waiting for you, but try to find out the cause of the A/C clutch engaging first.

check freon levels!!

NYCGPS: "Unless you turn defrost on, the clutch shouldn't engage at all."

In my experience, actually not a correct statement - at least on my 03 build MT. When you have the cabin controls set to 'floor only' the AC compressor will briefly cycle on about every 30 seconds. Don't ask me why it does it in this case, but doesn't do it when the switch is set to split between floor and dash, but I have often wondered how many others having "mystery" hunting idle episodes are actually seeing this eratic behavior as a result of this AC compressor cycling phenomenon.

To my specific issue on why this cycling was killing my idle RPM's - looks like I got a bum unit from Mazda so it is coming off and another one has been ordered.

you are in the year for this issue.

https://www.rx8club.com/showthread.p...p=15&styleid=8

post 8 in that thread.

beers :beer:

Yup - been on that side of the AC story for a long time. Had the new amp installed shortly after it came available. Didn't bother with the reprogram as its no big deal for me up here in NH, but for those that are interested the reprogram instructions are below. Not the same as the probelm I was having with the AC compressor affecting idle RPMs, but worthwhile info none the less. :wiggle:

AC reprogramming instructions
it only works if the build date is after 9/03, but it may work if the AC compressor/amp was replaced under the TSB

1. Make sure the car is off AND the HVAC fan is off AND the A/C on/off button is off.
2. Press and hold the front defroster (on the left) AND air source (recirc/fresh air) buttons
3. Continue pressing the buttons in step 2 and turn the key to ACC for 3 seconds
4. Continue pressing the buttons in step 2 and further turn the key to ON (NOT START) for 3 more seconds.
5. Verify the programming update by observing the REAR defroster LED blink 3 times.
6. Release the two buttons from step 2 and start the car.

When you turn on the A/C with the MODE button set to FACE and turn the thermostat to full COLD (max counter-clockwise setting) the RECIRC should automatically engage. In addition, the amplifier should put out colder air (~ 5-10 degrees F colder and not just from the RECIRC setting) and the compressor will not cycle nearly as often (which some of us found annoying).

Note: This programming change is not persistent. If the battery is fully discharged or disconnected the procedure needs to be repeated to re-enable the settings.

this takes all of 10 seconds to do, and everyone that's done it has noticed a dramatic difference.