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Hello all,

Hopefully someone can help me out here.

I own a 1990 300 CE with automatic climate control. It's not working. It's been to 4 mechanics, with the last one being a W124 specialist who's always been able to handle everything related to my W124 without needing to search endlessly. He has no idea how to solve this. It's now at it's 5th mechanic who has been able to get the airconditioning working, but that's about it. He runs a rather big climate control company here in the area (Rotterdam, The Netherlands) to which a lot of Benzes are send to when Mercedes doesn't know what to do with it. He's got no idea why the system is faulty either.

Here's the issue is:

I've got 2 control panels. Both should be good as they've been tested in other cars.

Installing control panel 1 (the original one): No reaction from the buttons, heater on top temperature and fan blows full speed. It can't be turned off.

Installing control panel 2 (replacement): Temperature can be switched to either zero or 40 degrees and fan can be set at three different speeds (with "auto" being one of them) but can't be turned off.

I currently have control panel 2 installed as that one gives me at least a few options.

I can press the recirculation buttong but it never works. However, occasionally the light in the recirculation button starts flickering and both the fan and control panel shut down and I get hot air instantly. Occasionally meaning once in a blue moon.

Anyone have any idea?

Many thanks!
 

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Exactly which climate control system did your car come with from the factory?

European spec cars were available with 3 different systems. The basic one has just 2 temperature dials, the semi automatic one is the same as basic plus air conditioning, and the full automatic type only has 1 temperature wheel and five buttons.

Also be aware that the systems are not interchangeable in any way shape or form, and each type requires its own specific form of diagnosis and repair.
 

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It's the one with 1 dial, 5 buttons and then 3 buttons on the side. It's the full automatic type.

The operating unit in the dash can be exchanced as long as it's one for the full automatic type. Hence me saying it's weird how 2 operating units work differently in my car yet the same in another car. It excludes the operating unit in my car from being faulty as they both work in other cars. They've been tested.
 

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It's the one with 1 dial, 5 buttons and then 3 buttons on the side. It's the full automatic type.

The operating unit in the dash can be exchanced as long as it's one for the full automatic type. Hence me saying it's weird how 2 operating units work differently in my car yet the same in another car. It excludes the operating unit in my car from being faulty as they both work in other cars. They've been tested.
Are the two cars the same models? Most of the climate controls are model specific and are not interchangeable.
 

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With the fully automatic type, replace the strip fuse on the driver side strut tower first and foremost. Doesn't matter if it "looks OK". Ditto for all the torpedo fuses in the main fuse box using the updated copper core ceramic type such as those made by Flosser. Dirt cheap part, and part that is known to cause strange issues.

The fact that your recirc light flickers on and off randomly tells me the system is getting power but not enough current (Amps) is being let through hence the fuse.
 

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One more thing, with the engine idling at full operating temp measure the voltage at the battery with and without the climate control turned on.

You should see a number between 13.5 and 14.5 Volt. Report back with your reading.
 

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When switching out climate control panels, did you ever have one of the plugs come apart and the wires pop out of their respective positions? I'm wondering if there are a couple of wires misplaced.
 

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Discussion Starter #9
I apologize, I swore I had replied here last and was waiting for replies. Anyways...

When switching out climate control panels, did you ever have one of the plugs come apart and the wires pop out of their respective positions? I'm wondering if there are a couple of wires misplaced.
I didn't, but someone else clearly did. It's been at the garage and after installing a new blower regulator the fan still wouldn't shut down. A mechanic downloaded the wire schedules and started going through all of them individually. Eventually he opened one of the plugs going into the panel and the wires had all been replaced from position 1-14 to 3-16. Or something to that extend. It turned out to be an instant fix, according to him, and the car was returned to me.

However, I do have some questions;
1. After opening the center console one of the vacuum hoses in the dashboard wasn't connected to anything. The mechanic said he fixed it by putting a cap on it so air couldn't escape anymore. However, when turning on the climate control I always hear a sound coming out of the center ventilation shafts, if that's the right word?

https://photos.app.goo.gl/7R11GMy4sMdMrEBVA

The mechanic says the sound is normal "but might be more audible due to a faulty vacuumpod on the engine compartment". Whatever that means? Sometimes, after driving the car for several days, the blower fan won't start running after driving for several minutes. Can anyone tell me what's happening here?

2. After starting the car and pushing AUTO on the control panel the fan starts blowing full speed, then turns softer, but never gets remotely close to zero or the minimum speed. According to the mechanic this is because there's a button Minimum. If you want it at minimum you should put it at minimum. However, doesn't that make the purpose of the AUTO setting irrelvant? It's as if I've got 3 settings now:
a) High speed
b) High speed, then middle speed
c) Low speed

Can anyone tell me what the auto setting should do exactly?
 

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FSM climate control operation

Up in the top section, there is a sticky 124 DIY thread. In there is the Factory Service Manual. Here's a link to the section on the Climate Control system operation:
http://www.w124-zone.com/downloads/MB CD/W124/w124CD1/Program/Climate/83-600.pdf
Give it a read through.

Your question 2, the mechanic is correct. The three automatic settings are, to follow your list:
a. High Speed.
b. Almost high speed slowly slowing down to almost low speed as the interior heats up or cools down.
c. Low speed.

There aren't any vacuum pods in the engine compartment, only around the HVAC unit under the dashboard. Depending on the outside air temp, the blower sometimes won't operate until the coolant gets up to some minimum temperature. Also, there is one plastic vacuum line under the dash near the gauge cluster that remains open (not connected to anything or capped) as it's a vent.
 

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Have you read about your HVAC system in the owner's manual? With everything set on "auto", the fan speed will vary from almost "high" speed to something very near minimum. Much of the fan speed is dependent on where you have your temp wheel set. The overhead light has a small grill where interior air is drawn in via the sampler motor, which sends the air to the temp sensor, which varies the fan speed.

There isn't a vacuum pod under the hood of the car. Use our search tool and look up "vacuum block distribution". The distribution block is behind the glove box/passenger airbag.

As for the fan delay at initial start - normal. In the winter months, the fan will not blow until the coolant temp is to a point that warm air comes from the vents..when keeping the system set to automatic.

Jayare

Sent from my XT1710-02 using Tapatalk
 

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Discussion Starter #13
Many thanks for these replies!

Have you read about your HVAC system in the owner's manual? With everything set on "auto", the fan speed will vary from almost "high" speed to something very near minimum. Much of the fan speed is dependent on where you have your temp wheel set. The overhead light has a small grill where interior air is drawn in via the sampler motor, which sends the air to the temp sensor, which varies the fan speed.
Yeah, I just read it. The thing is, on auto setting it never gets near minimum. It goes from high to a little bit less high, but rarely ever does it get to near minimum. Whenever you're driving it never gets quiet in the car if you've got it on Auto, if you know what I mean? It's not a particularly relaxing drive if you're always listening to the sound of the blower fan.

However, another thing I've noticed is this;

Sometimes when the blower is on Auto setting there's barely coming any air coming out of the vents. It's as if it tries its best to cool the car down but the ventilation shafts are closed. Is this managed by the same vacuum pod in the dash?
 

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Has someone replaced the blower motor?

Sent from my XT1710-02 using Tapatalk
Yes, both the blower motor and the blower resistor have been replaced. The blower motor has been replaced about 5 years ago and the blower resistor is brand new.
 

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Many thanks for these replies!



Yeah, I just read it. The thing is, on auto setting it never gets near minimum. It goes from high to a little bit less high, but rarely ever does it get to near minimum. Whenever you're driving it never gets quiet in the car if you've got it on Auto, if you know what I mean? It's not a particularly relaxing drive if you're always listening to the sound of the blower fan.

However, another thing I've noticed is this;

Sometimes when the blower is on Auto setting there's barely coming any air coming out of the vents. It's as if it tries its best to cool the car down but the ventilation shafts are closed. Is this managed by the same vacuum pod in the dash?
This is normal....I often push the switch for Low fan because on Auto it stays too noisy messing around trying to sustain the temp you set. The only caveat there is in the winter, because Low won't give you enough heat throughout.

Truthfully, the Germans screwed the pooch on the ergonomics of this system.

Kevin
 
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