Intermittent AC - out of ideas

[FellowsheepTech]

Originally Posted by andrewwynn

If you can command on compressor with the tool, you should be able to see the evaporator temp drop to confirm its working. It feels like safety is intermittent disable eg loose or short wire from pressure switch.

The tool activation lasts 30 seconds, & not sure I can navigate from there to live data in time. Worth trying though.

Drove it this morning with same behavior; cools after driving a bit & once stopped & idling it didn't. Since it was still cooling as I pulled in the driveway, I was able to jump out & see the aux fan working

Taking the X35D up to my dad's for the weekend, so will resume troubleshooting next week. Appreciate all the input!

[andrewwynn]

You can put your hand on the cool pipe that will also confirm activation.

From history, the symptoms line up with the variable compressor not variable-ing. I read once there is a trick to get it to stay in high compression mode to avoid replacement

[upallnight]

Originally Posted by FellowsheepTech

The tool activation lasts 30 seconds, & not sure I can navigate from there to live data in time. Worth trying though.

Drove it this morning with same behavior; cools after driving a bit & once stopped & idling it didn't. Since it was still cooling as I pulled in the driveway, I was able to jump out & see the aux fan working

Taking the X35D up to my dad's for the weekend, so will resume troubleshooting next week. Appreciate all the input!

When you first start it and switch on the AC, if it isn't cooling, raise the engine speed to 5000 rpm. See if it will starts to work afterward. If you suddenly get cooling after raising the engine to 5000 the variable displacement valve in the compressor is bad and you can replace it or replace the compressor. Either repair will require you to remove the refrigerant from the system and make the repair. If it was my X I would just replace the compressor.

[FellowsheepTech]

Finally back to this after holiday road trip & R53 rescue mission.

Originally Posted by upallnight

When you first start it and switch on the AC, if it isn't cooling, raise the engine speed to 5000 rpm. See if it will starts to work afterward...

Nope

[upallnight]

About the thing you haven't changed is the compressor, and it's the compressor that makes the magic happens.

To Quote Mr. Spock, “When you eliminate the impossible, whatever remains, however improbable, must be the truth.”

[FellowsheepTech]

Backed up a few steps & tested grounds & signals with test light & multimeter.
* Clutch tests good, as does activation signal.
* All grounds good (including low/high pressure switches)
* Can ONLY activate fan from tool. Will not activate from control panel (either, I have two). Can not confirm anything on small, black control wire for fan. Assumed signal there if activated by tool, but now questioning that.
* The ONLY code I have, which is generated every time I try to turn on A/C is DME: Fan activation

I was ready to replace compressor & condenser as last resort, but the only real data I have is still pointing to the fan (also new, but sourced on Amazon). I'm going to try another fan (still not the $4-600 OEM), and while I'm replacing will unwrap & inspect the wire back as far as I can get. No clear damage or tampering noted thus far, but the whole branch is wrapped in plastic electrical tape that doesn't appear original. Could be, but...

Also going to replace radiator fan clutch at the same time (PTA!) since it's cheap & the only piece of cooling system that's not new.

[FellowsheepTech]

Backed up a few steps & tested grounds & signals with test light & multimeter.
* Clutch tests good, as does activation signal.
* All grounds good (including low/high pressure switches)
* Can ONLY activate fan from tool. Will not activate from control panel (either, I have two). Can not confirm anything on small, black control wire for fan. Assumed signal there if activated by tool, but now questioning that.
* The ONLY code I have, which is generated every time I try to turn on A/C is DME: Fan activation

I was ready to replace compressor & condenser as last resort, but the only real data I have is still pointing to the fan (also new, but sourced on Amazon). I'm going to try another fan (still not the $4-600 OEM), and while I'm replacing will unwrap & inspect the wire back as far as I can get. No clear damage or tampering noted thus far, but the whole branch is wrapped in plastic electrical tape that doesn't appear original. Could be, but...

Also going to replace radiator fan clutch at the same time (PTA!) since it's cheap & the only piece of cooling system that's not new.

[andrewwynn]

The control wire for the fan is PWM. The fan goes through a test at every key on and if it fails that test you'll get the fan activation code. The code reader likely just sends pwm signak too the fan doesn't care about that startup test result. Does your fan turn just as little when you first turn the key on?

[FellowsheepTech]

Originally Posted by andrewwynn

The control wire for the fan is PWM. The fan goes through a test at every key on and if it fails that test you'll get the fan activation code. The code reader likely just sends pwm signak too the fan doesn't care about that startup test result. Does your fan turn just as little when you first turn the key on?

No, it does not

[andrewwynn]

I wonder if you can trick it by spinning the fan but I don't know how the computer measures that it spins e g is it measuring induced voltage.

History shows if the aux fan fails startup test AC will.not operate