Your 124 should have a timed recirc switch above the ACC controls. It's only effective if the actuators are in good shape. Remove the glove box liner to expose the ACC actuator switch bank, identify the lines to the recirc actuators and test for vacuum tightness.

Sixto
87 300D

My pods and functions are right-on. Took the dash off, replaced all, mity-vac'd everything, checked out recirc timer/relay, etc.

What I asked (or am trying to ask) is does the ECC, when cooling, automatically shift from fresh/80%/100% as required?

Thanks.

.

Oh, I thought you wanted a way to effect recirc for testing vent temps.

ACC closes the recirc flaps to 80% or 100% based on mode and temperature conditions. From what I remember reading looong ago, there's also the variable of how long the recirc flaps have been closed. ACC eventually allows in fresh air.

Sixto
87 300D

Yes, it does. The basic decision on fresh vs. recirculated air is made on the delta T between the set temperature and the interior temperature of the car. Beyond a specific detlta, 100% recirc is used. As the interior temperature approaches the setpoint it switches to 80%, and then fresh air.

As Sixto alludes, there are other factors as well. A complete description resides in the 124 climate manual. The above description exhausts what I can recall from memory.

SJH, there is a chart for what you ask in the FSM.

The pdf from the FSM for a description of the ACC function is 2.11mg, which can not be attached on this site. If you give me an email that allows that sized download, I'll send it to you.

If these FSM excerpts are inappropriate let me know and I'll remove it.

Thanks again.

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Oh man! If Mercedes had gotten a good a/c unit in these cars, these a/c problem threads wouldn't even exist. Mercedes a/c system has got to be the worst, or at least one of the worst, of any luxury car brand. Problem city with these, plus the blower squirrel fans, even brand new, are noisy.

Since my temp only reached 62, my mechanic figured freon leaked out, put in a dye to find the leak at a later date, and added some more freon. Big difference in the cooling, right off the bat, so I guess I could say problem solved, it was low on freon due to a leak, since he topped it off just last year.

He said it brought it down 10 degrees, which would be 52. I haven't measured it myself but will later today.

Your system is low on refrigerant and Mercedes has a poorly designed system that won't cool.........???

..............well...........OK then.............

Did you even bother to read post #3 of your thread?

How well does the a/c work for your friends that are driving 1991 model year Lexus automobiles?

how about the 78 model lexus?

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Oh c'mon guys. You mean to tell me the Mercedes a/c system is AS GOOD, or BETTER than even standard model cars, like Toyota's and Honda's?

My system is low, because the freon leaked out, but I've had previous issues with it, having to get parts replaced.

Anyways, I did check the temp now that more freon's been added in, again, my guy put in dye so he can check later down the road to see where the leak is. At the time, he did a quick check on the temp, but yesterday, I drove the car for a while, and it was down to 40 degrees. Quite a nice difference on a warm day.

But that's the end of the story, at least for now, that it has a leak, and we'll try to find it in the future months.

Thanks for all your help.

What is your definition of a "good" system and where is your data to support your definition?

I have the data on two of my vehicles and can, without any qualification, define the performance of the systems.

Brian, I'm betting you're are a better mechanic than me, so I will defer to you. If you think MB ac units are just as good as any other car, I won't argue with you. However, from my point of view as a driver (not a mechanic) of 2 MB's, both W124's, I have found they cost me a lot of money on the a/c's, with multiple repairs (my current one I'm posting about on this thread, a 1991 300d with 167k on it), I've had repaired 4x in 4 years.

I've replaced the blower fan and regulator cable I think it's called that goes to the fan, then a MB specialist mechanic replaced a (?) drier or something once. I've had more freon added last year, then more this year, so we now know there's a leak. In all cases except this last recharge now just 3 or 4 days ago, the a/c has never been "cold". It'd been adequate at best, but no more. The other day, as I posted, it is blowing now at a very nice 40 degrees, and feels great. That's the coldest that car has ever blown, in the 4 years I've owned it.

On my 1988 300 CE that I had 14 years ago, ditto with that. It never cooled well. I took it to a MB specialist at the time, who "fixed" it for $500 (I'm assuming now he added a bit of freon for $500), and it didn't blow cold. I took it back to him 2 weeks later, and he made it like he was doing me a favor to work on it again. When I got it back, it blew a bit cold, but very marginal.

Also on both cars, I get the fog line on my windshield due to the pods not closing tight, so on a nice dry summer night, I'm the only one with my windshield wipers on. I've also seen many MB's here in Atlanta, and online, with tinted windows, which to me, is another way of saying their a/c's probably don't blow cold, and ones I've seen advertised, often say, "a/c doesn't blow cold, it probably needs a recharge".

But if you think MB's don't have more problems than other cars, I will believe you. My view is just from a driver's point of view and casual observations of what I've seen (ie, I haven't kept formal track of how many work, and how many don't). I'm also under the impression that BMW's did not have very good a/c's, either. From all the problems I've had on my 2 MB's a/c's, and probably $1,200 later, it seems to me their a/c systems leave a lot to be desired.

If I could wave a magic wand, one thing I wish MB had on these cars, is a simple low/med/high setting, and a quieter fan! Low is too low, it hardly puts anything out at all, so I nearly HAVE to switch to the annoyingly-loud auto or high settings ("auto" is typically high or low, the variable 'medium' setting it puts out temporarily doesn't stay around very long). I think on Honda's or Toyota's I've had of the same years, low is quiet and puts out a fair amount of air, and even a notch or 2 up on the fan is still reasonably quiet.

I need to convert mine back to R12.. Perhaps a winter project for me.

Jeremy has a nice process for adjusting the fan speed to address some of your concerns.

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