Intermittent A/C problem 260E

Just spent another $550 on my a/c recently. Replaced the speed sensor on the compressor. New ETR switch, (missing due to original mechanic not replacing it) Evac system and recharge. The system was overcharged as well by previous mechanic. The a/c will still stop working unexpectedly and seemingly for no reason. If I quickly turn off the engine and then back on (while driving) it will kick the compressor on but then will stop working again. 2 (two) mechanics seem to be baffled but this a/c behavior. Just replaced the climate relay today but the problem persists.

Any thoughts? Geeeeeze! Waaaaay too much money to spend on A/C!!

[amg280]

I have the same problem on my 400E. seems to be more persistent when I rev it out higher (3500 to 4000). Then it blows out ambient air. If I shut it off and restart it, it is fine. Could the belt be too loose? cause the compressor to not "catch" up when engine revs up fast? Im puzzled as well.

Hopefully someone can shed some light on this. My old 190 2.6 had the same problem.

[Mike Murrell]

If the compressor speed sensor detects a mismatch in speed between the compressor and the engine's rpm, the a/c is shutdown. It takes a cycling of the ignition like you're doing to reactivate the a/c.

Sounds like the speed sensor is defective or perhaps it's installation.

There have been numerous posts here on this issue. It's pertinent to serpentine belt systems like the M103.

[jcyuhn]

The most common cause of this problem is that the clutch *is* slipping when the compressor is cycled on. It's because the clutch gap is out of specification - it gets wider as the friction materials on the clutch wear. It's easily checked with a set of feeler gauges. Should be 0.50mm, plus or minus 0.15mm. When it gets up around 0.80mm you'll start triggering the compressor cutout function of the Klima relay. That's what is happening when the a/c quits until the car is restarted.

Can also be caused by just a little bit of oil on the clutch friction material. Try using a can of spray brake cleaner, or even just simple green. Thoroughly clean and rinse the clutch areas on the compressor. Then give it a shot. It'll definately cutout while still wet, but when dry it may work for you. I know of one person who fought this problem for a long time, and finally fixed it with a 2 dollar can of degreaser.

[mercedes230.625]

My 190E 2.3 also have the same problem. A/C compressor kick on few second, then stopped. I just replaced evaporator, recharge the whole system. 100% sure on leak..... I will clean the A/C clutch tomorrow and try it.... Hopefully it works after clean it.

[jruanoru]

I a problem with my A/C, Is it the same problem????:

When I ignite the engine and I turn on the A/C I put the maximum power of the flow (I touch the button for the flow speed to the maximum). The A/C works fine, with the maximum speed of the flow... but after 5 or 10 minutes, the speed of the air flow decreases, I don't touch any button, I don't touch nothing .

The A/C decreases the speed automatically after a few minutes but I don't know the reason. After it, I can't increase the speed of the flow to the maximum power. The display of the flow power marks the maximum power, but It isn't true, because it decreases, but the display marks the maximum power... why????

Thank you in advance.
Regards

[James L]

at any time do your hear a flapping shut noise behind the middle dash vent or glovebox area? if so it is the main air flap that controls the amount of outside air to mix with the desired climate control setting. it needs to be shut all the way when maximum cooling is set.

[bcm]

vERY GOOD POST YOU GUYZ, THANKZ.

[jeff-abalone]

Originally Posted by mercedes230.625

My 190E 2.3 also have the same problem. A/C compressor kick on few second, then stopped. I just replaced evaporator, recharge the whole system. 100% sure on leak..... I will clean the A/C clutch tomorrow and try it.... Hopefully it works after clean it.

Following up my A/C!!! I shampoo the engine bay last Sunday. Specially in compressor area. Today, thursday.... the A/C works perfect. Hopefully, it will continues working until the end of the summer this year...

[pesuazo]

Sometimes cold solder at the climate control unit will cause an intermittent operation of the A/C

jcyuhn is our resident, 124 A/C expert and, as always, is right on the mark with this one.

The belt or clutch slips triggering the system shutdown. As he professes, the clutch is the likely culprit, but a slipping belt or an overcharged system will yield the same result.

Good luck,