mijotu

Hey Folks,

(Forgive me for what may very well be a tired topic in this, my inaugural post. But, if you've enjoyed the results of forum searches, you might sympathize with my query!)

2004 E320 Wagon

Knowns: A/C was recently inspected by dealer. System recharged, dye added (no leaks detected), no codes reported. A/C cools to spec when functioning.

Issue: A/C will either activate upon engine start, or it won't. Once on, it stays on. All vents behave uniformly. Issue can sometimes be resolved by restarting the engine—or by toggling the A/C on/off from the control unit—once or twice, but not always. Appears to fail during the hotter part of our Texas summer days, less so in the mornings. Haven't correlated issue to length of run time prior to outcome.

Does this sound familiar/common? I'm happy to provide any additional troubleshooting at you request to aid in isolating the issue for me, and I thank you in advance for any assistance.

kajtek1

Do you have climatronic with REST button that allows sensor reading?
It would be very easy troubleshooting with it
Other than that you need to check AC for codes and do sensor readout as guessing from crystal ball which one of 8 sensors is giving bad information is long shot.

mijotu

I agree. My crystal ball is solid up to 3 sensors, but 8 lies in the 4th deviation...

Yes! There is a Rest button. I had no inkling that it could be useful, or how it might function at all. (My vehicle is far simpler — this is the wife's steed.) Whether it's of the Climatronic variety I don't know, unless that's a given.

So, where might one go from here?

kajtek1

read the sensors 1-8 once in the morning with engine off, once in hot afternoon after you restart the engine and post numbers here.

mijotu

Unfortunately, mine does not have a readout in the control panel. There is an LCD screen below; however, there was no discernible response to my pressing 0 + REST with the key turned to ON.

Is there a bespoke method for our model, or is it time to hook it up to a thingy?

kajtek1

I did not check the video, but seems there is an error in it.
Press REST only for at least 5 seconds and see if the display change?

nivram13

Is the air con intermittent or the blower motor?

rapidoxidation

I'll take over on that question cuz it seems the n00b isn't going to be back: Blower motor. On the day's initial startup, it sometimes (three times or so over the summer, and only when the car has been sitting in the hot sun) won't turn on even though the buttons on the dash light up. Turning the car off/on will resolve the problem.
Ideas?

nivram13

Had similar issue the blower motor regulator was at fault I've gone through a couple of these, which display the symptoms of the blower working intermittently.

An easy enough fix if your going to replace it don't get a used part it will only fail again, grab yourself a new Behr one.


Could alos be the blower motor but highly unlikely.

https://www.fcpeuro.com/products/mer...mer-2308216451

jimbo1763

+1 on the blower motor regulator. Replacing it fixed mine which had similar symptoms.

travhwrd

having the same issue, replaced the regulator with a brand new unit from "koolman", looks different but fits and matches the part number. any ideas now?
works when it wants to




https://www.amazon.com/Mercedes-Benz...ower+regulator

mijotu

Forgive my disappearance, Folks — seems I was no longer receiving notifications for this thread!

Air con is intermittent. The blower performs normally under all conditions.

Also, I do not have a readout on the controls for the suggested diagnostic. Will data be presented on the LCD panel instead?

StarvingArtist

This might be a long shot, but I read about the internal lining of the low pressure pump hose collapsing as the pump is sucking on it, and blocking the flow. E55 forum a couple years ago.

kajtek1

If you can't read the sensors on climatronic, you need to use a computer for it.
I like the LCD readout and on our 2008 model I replaced the climatronic with the one that allows troubleshooting.
They sell for $40-60 on ebay.