Can I always leave the A/C on?
 

Will it ruin the A/C system sooner if I leave it on all the time, when turning off and starting the car? I heard that it can ruin the compressor if it's left on and the engine is turned off. I just want to know if that's true. Because of that, I always turn the system off when turning the car off.

I don't think it makes a difference.

I can say though, that it is best to not set the wheel in the fully hot or fully cold position, and also to not set the fan blower speed to continuously on "high" or "low", but rather use the "Auto" button.

Drivers have the feeling that full heat or full A/C will get the passenger compartment to the correct temperature fastest.

This doesn't allow the system to work as designed.

To get the longest life from the automatic climate control system, allow the system to exercise all components.

If the temperature inside the car is more than 4 degrees away from the setting on the temperature wheel, the system will use full heat or full A/C regardless.

As the interior temperature approaches the setting at the climate control panel, the automatic functions will slowly reduce blower speed.

Allowing the system to work in its automatic mode, with all components functioning, will prolong the life of the system.

When flap controllers and valves (vacum operated) don't move for long periods, they tend to stick in position and ruin the component.

Zero i LOVE your icon,, two words,, "CHARLIE MURPHYYYYYYYYY!"

Believe it or not, the service manager at the local M.B. dealer has told me that if you switch to "EC" (turning off the compressor on the A/C but leaving ON the fan) three to four minutes before you turn-off the car at the end of the day -say your last drive going home-) it could save the life of your evaporator, or at least extended considerably.

This is very useful considering how problematic the evaps can be on W124s and W140s.

It is Sunday morning after a time change, so my telepathic skills are running a little weak this morning. What MODEL and YEAR are you driving?

We don't know if this is a climate control or a manual system. For example, with a 124 car, the climate control will automatically delay engaging the compressor to give the engine time to build oil pressure.

The compressor being engaged while starting the engine won't hurt the compressor, it will hurt the engine because of the added load while oil pressure is building up.

The compressor and clutch are designed to kick on and off while the engine is at speed so it doesn't hurt the compressor.

If you do have a 124 or newer car, just set the temperature where you want it, push the center button and FORGET about it. You can turn the temp dial a few degrees cooler or warmer after temp has stabilized, but let the thermostat do the work. By maxing or mining you will get to comfortable temperature no quicker. The system will get it to the set temp as quick as it can.

Good luck,

I think zeronero has a W124 400E.

i'm in the industry and so we are reminded...
 

prior to starting any vehicle to make sure all a/c's are in the off position. so i applied this to my own vehicles and took it a step further and would do exactly as a.rosich said and turn off my a/c 5mins before to get the moisture out of the system.i never get the bad smell when i return and use my a/c.it's good to know that there is a side benefit in taking care of the evap.as an extension of this REGARDLESS of where you live,it would be a good idea to run some heat through the hvac system to keep everyhting 'lubricated':)

:eek: I forgot, what can I say:(

suginami is right, a '92 400E

So the automatic climate control in the W124 automatically shuts off the compressor and other components before the engine shuts off and then at start up waits until the right time to engage, it's that advanced!???

So that means it pointless to turn the system off when turning off the car?

It does not know when you are going to shut off the engine, so it can't turn off the a/c ahead of time, but as long as the evaporator drain is not plugged there is no need to turn off the a/c before turning off the engine. By the same token whether the compressor is disengaged before the engine is shut off makes no difference as far as the system goes. The compressor will stop its work either way and the pressures will equalize through the expansion valve.

When starting the engine, the climate control will not allow the compressor to engage for a delay that allows oil pressure to build and stabilize.

The 124 Climate Control will last longer and be more effective if you just set the temperature that you like and forget about it, winter or summer. Leave the center button pressed and the auto fan button pressed.

Mine has been this way for 6 years and I have had to do nothing to the system whatsoever.

Good luck,

In my mind, an automatic climate control system, like those installed on W124, are automatic and does not require human intervention.
Except for the rare few time I switch my system to "defrost", it has been running on full "automatic' for 14 years and 390K without ever missing a beat. I still have the original R12 refrigerant in my system.
There is no reason to "play' with the temperature settings as it will not cool or heat faster, whatever its position.
Leave it alone.
jackD

For the 1994 E320 I've been in the habit of doing what Larry described above (using the auto button with the center button depressed) and letting it run all the time with one exception...

Before I shut off the engine, I hit the "0" button on the right side and actually turn off the system. When I restart later, after letting the engine warm up a minute or so, I hit the center button again. They system has worked perfectly for many, many years.

Am I reading correctly, that it's better to not bother using the "0" button to turn it off and just leave the center button pressed all the time?

Exactly.

More precisely, if the temperature inside the car is more than 4 degrees away from the setting on the temperature wheel, the system will use full heat or full A/C regardless.

It appears that everyone here understands the basics of a thermostat so I don't think I will hurt anyones feelings if I say this here.

It never ceases to amaze me how many people just flat don't understand how a thermostat works. I'm not only talking about cars, I'm talking more about indoor thermostats. I've seen so many people go to a thermostat when uncomfortable and turn it as far as it will go. They just don't understand that this will not heat them or cool them any quicker.

I worked for a software company for many years that was founded and run by a very smart and hard working man. His education was electrical engineering as is mine. I remember many times being in our conference room and the temperature would be a little too hot or a little too cold and he would walk over and max the thermostat. For him it was particularly bad. You would think that someone educated in technicology, particularly electronics would understand a basic bimetallic strip and electrical switch.

Have a great day,

Larry: Myths are also frequent with professional mechanics.
last week, I was told by a mechanic with 30 years experience that I should not park my car so I have to back-up in the morning instead of first going forward. He said: Always park your car facing the street in your diveway.The transmission lubrication system does not allow for any oil circulation in the transmission in reverse gear. Oil will only circulate when the car is in a foward gear. Yyeeaahh.
JackD

Sexist Remark
 

I have yet to meet a woman that understands a thermostat. Most men don't either, but a few of them do. I find it most helpful to tell the offending party that I will beat them to a pulp if they touch the thermostat - that seems to work well for me, anyway.

Larry,

How true. So many people have this idea that if they turn a thermostat to its extreme setting the temperature will change faster. They don't seem to appreciate that in a closed loop system with feedback the heating or cooling is either on or off as required until the desired temperature is reached.

I think I finally have convinced my wife to leave the temperature controls alone in our 300TE but I still see my father setting those in his E320 coupe at extremes. Unlike the fully automatic system you got in the US, most W124s in Australia got the (very reliable) manual climate control system which still was a closed loop system (except with separate left and right temperature zones and manual fan speed and air direction controls). I even submitted an article to our MB club magazine explaining to owners how the sytem should be used after noticing that most owners constantly fiddled with the temperature controls and often set them to extremes. Even the owner's manual recommends 22 degrees C as a comfortable year round setting.

As to the topic of this thread, we usually leave the aircon enabled year round (the EC economy button disables it) since the compressor will only engage should the cabin temperature require it anyway.

Attached image shows the system most of our W124s got (note dual temp controls calibrated in degrees C).

That's what I do, but since there's no reason to do it I'll just leave it on from now on.

have you ever seen a person push the elevator button once it was already lit?or how about the person who presses the street-crossing button time and time again.most people understand these actions don't accelerate anything but it releives some kind of nervous tension.that's all

Actually, even with the heat on, the a/c compressor is still running to remove humidity from the air (by design).

Just as a clarification, this may be the case with the automatic climate control system (with horizontal row of buttons and single temperature wheel) on North American delivered W124s. On the "manual" climate control system we got in Oz (as shown in previously posted pic) the compressor only engages when the cabin temperature is high enough to demand it. To have it operate at low ambient temperatures to reduce humidity (ie. at same time as heaters) the "demist" function (uppermost of the three buttons) must be activated. The only other situation that would operate the compressor together with the heater would be in the (unlikely) situation where the temperature wheel for one side of the car is set to a significantly lower temperature to that for the other side. The EC mode (middle button) disables the compressor.

Chip - I hear you man. Most women (smack!) are like hampsters on the hamster wheel when it comes to the thermostat. Too hot? Wheel it to max cool. Too cold? Wheel it to max heat. Drives my buddy and I nuts (our wives in this regard).

Larry and Paul - I've followed your advice on this subject, and have my wife educated on using the ACC in her E320. Thanks for the education. Paul - come back to Dallas soon - love to meet up with you, Larry and the other 'locals' again.

I'll be back in Dallas from June 2 - June 5.

I'll probably be flying back home the evening of Saturday, June 5, so a Friday, June 4 dinner would work for me.

Mark it on your calender.

Friday, June 4 it is. We should start a thread here and in the events forum once we nail down time and place.

Where will you be staying this time Paul?

Have a great day,

NOT applicable to Texas in the summer or the Dakotas in the winter:D :D :D
Its just to much of an extreme, Were not living in the perfect weather of Sothern California

Dave

Dave,

The thread was talking about the 124 climate control. It does a better job than the 123 automatic unit and can be set to the temp that you desire. The system will automatically get you to that temp just as fast as if it were turned to the extreme.

It is able to operate like the thermostat in your house where regardless of if you set it five degrees colder than current temp or max it out, is just turning on a pair of switch contacts so it will not get the temp to the set temp any faster.

Dave, do you know enough about your schedule yet to know if you can join us for dinner the evening of June 4?

Have a great day,

I'll be staying at the Sheraton across the street from the Wyndham Anatole.

Okay then, you'll be close to the West End again. Barbeque?

Let us know and we'll pick a spot and kick off the advertising campaign.

Have a great day,

What's the matter with ya'll?

Everybody knows the thermostat works just like a volume control...The further you turn it to cold, the colder the output and the further you turn it to hot the hotter the output.

Why do you think it is adjustable like a knob, and clearly not like a switch?

The one in my house is the same way.

Simple physics.

brewtoo
You sound like my wife
Don't think simple physic, think simple logic.
JackD

Barbeque sounds great. Let's do it.

ok guys- I hate to be the first to drop out, but friday nights are impossible for me. Really, any night but Friday is doable. I'll just have to wait until :( the next time around.

Give me a chance to work up my list of questions....

71Rcode,

I'd hate to move the date away from Friday as it is a day that most guys can stay out late.

However, if I'm available Thursday night, maybe you and I can hook up for dinner (if your wife lets you out).

I'll contact you when it gets closer to June.

Paul - that might be perfect. I'll check with my wife's schedule (jewelry party hostess) - and let you know. Yes, Friday would be ideal for everyone, I'm sure. That's just the night my church band rehearses :p --- so that night is always out for me. Looking forward to it man...

brewtoo,

Are you being facetious or are you serious?

Paul,

I will start posting for Sonny Brians. What is the earliest time we can all start getting together?

Have a great day,

I think 6:00 pm would be fine.

Hate to bust in on this thread, but since my comment relates to 124s, maybe you all will forgive me. Suginami's comments about the system going to full it interior temp is 4 degrees out of whack either way and Larry's comments about setting and forgetting reminded me about this.

One of the most ridiculous sets of comments about my TE that I've ever heard came from someone I was dating a couple of years ago. The car actually was going to be hers, but...anyway...this person complained that the climate control system was too loud at the beginning of trips. (This in the middle of the usual very hot summer in Northern California....) The other part of that set of comments was that she didn't understand the ridiculousness of wheeling the temperature setting all the way in either direction. "I want it colder" was a stock phrase, when we'd just gotten into the car on a hot day and the system was already in overdrive trying to cool that enormous greenhouse down.

As long as I'm on this rant, the most ridiculous comment/question I've ever fielded in connection with my other automotive love, BMWs, came from the new owner of a 2002 5-Series who looked at the sound system in the dash of her new Bimmer and said to me "You're in securities. Are there special stations with market updates?"

(She referred to the "Business" designation on the sound system.)

It is purely coincidental that those two anecdotes involve women, but it also explains why I'm not involved with either one of them anymore.

Sorry David but the fact that they were women was NOT a coincidence. Call me what you like, but there are physiological differences between men and women. This is not chauvenism, it's scientific fact. Women typically do not handle logic well that involve spatial concepts. Again scientific fact.

As with all such concepts and rules there are exceptions.

Have a great day,

Larry:

I'd call you honest...and correct! I have to admit I was just closing up a call with my significant other (whom I think quite brilliant) when the email notice that you'd responded to the thread popped up. She must have been wondering what I was laughing about as we ended our call....

Oh, and the reason I edited this response was to make a remark about your spatial relationships comment. We recently went on a home-buying excursion led, of course, by our real estate agent who picked us up in one of those new-fangled Volvo SUV wannabees. The car/boat was fitted with GPS because, as our agent explained, she is "spatially challenged." While most of the houses which we looked at were east of Lake Washington where we live, there was one on the west side of the lake and our agent didn't know precisely where it was. Suffice it to say, not only is she spatially challenged, she ignored the directions from the GPS unit. I was in stitches. We finally found the place, but only because my fiance was able to convince our agent that the GPS system was probably right....

:mad: Your guy's comments are unappreciated. I'm sure that there are many men and women who fit those stereotypes you are so loudly proclaiming, and just as many who don't. One of the reasons I have liked this forum so much is the respect that most follks give one another. Apparently you guys are not a part of that respectful group anymore, and as such you degrade the friendliness and pleasure of this forum. If you would kindly refrain from making further comment like that, we could all get along a little better in this difficult world.

I'm not making negative comments toward anyone. I'm only talking about scientific fact. I did not say that men are smarter than women or vice versa. They are just different. There are many things that women are smarter about, but it is scientific fact that women are TYPICALLY weaker in the form of thinking involving spatial concepts. There are plenty of areas where the female mind TYPICALLY is better suited.

I'm not stating opinion, only fact.

I also said that there are exceptions to these traits.

Lighten up and don't be so sensitive.

Have a great day,

PS. I prefer fact over Political Correctness. LB

Now that IIIII have a w124
 

Did some reading on this thread over the wknd and going with the "leave on auto" theory" and just temp if needed. .... Anyway, I tried that at lunch and the sucker wouldn't kick down to blow less air:o , it is so freakin hot in South FL, I can not imagine that cabin ever reaching temp during the day here. I drove about 20 minute intervals 2-3 times and I don't think that sucker kicked down adjusting for cabin temp. Forgot to read outside temp, but usually is like 90 or so... oh well, so much for auto....

.... I am surprised I am the only one that might be "complaining" about the loud noise that a/c makes in auto (when it doesn't kick down) or in high... for a mercedes. I dont' remember my '00 being so loud...

yoshimura,

Do you have the auto fan button pressed as well as the center button in the horizontal row?

Have a great day,

Appears that your AC may need some attention. What is the air temperature at the vent?

I replaced the Aspirator motor, interior temp sensor and the AC control unit to get the system up to speed.

A good test for the aspirator is to see if a thin piece of paper will stick to the grill next to the dome light.

Worked in the evening
 

Larry - > Yeah, the center button "normal setting", per pg 22 in my manual, is the one I pressed.

Zafar - > I will check that near the dome light you mentioned, out of curiousity.

I tried it this evening by setting the temp dial up to about low 70's and the a/c did kick down, so it seems Ok. It is just so freakin hot in this town, that I don't foresee that thing kicking down during the day ever, lol.... going to try it tommorrow setting the temp up about the same temp, 70's, vs max cold.

I have been leaving it on when car is turned off though.

yosshimura,

Do you drive mostly short hops in town? How far do you typically drive and is it in traffic, freeway or a combination?

Have a great day,

My drive? am-rush hour, lunch-short hop, pm-rush hour.

It seems ok, b/c this am, I left the dial as it was last night, forgot the temp setting, but it was NOT at the coldest point, and it did kick down. Now, at lunch when I go out I bet it wont crank down b/c it will not have time to reach temp setting.

one more question
 

89 300CE

I like to drive with the sunroof/windows all open all the way whenever practical. While I understand the "set it and forget it" theory, would it make sense to just shut the system off (hit the "O" button) if I'm driving in my "almost ragtop" mode?

I know my climate system will not heat or cool the great outdoors!

thanks again for all of this site's excellent advice.

When you are enjoying the great outdoors, simply press the EConomy button. On the 124 climate control this is the second button from the right in the horizontal row of buttons. Then when you close everything back up, hit the center button again.

Enjoy,

My wrecking yard said the AC control panel is one of the most failure prone and requested items. If you want it to last- don't push the buttons any more than you have to, set it to auto and leave it alone! Up here I can leave the fan on low most of the year unless we have rear seat pax and then you need a little more air flow.

Dan

Leave the fan buttons alone too. Just press the auto fan button and forget it.

My $0.02,