C250TD - AC - blows fast and slow

[paulfoel]

Had my 250TD for a few weeks now and have noticed something strange with the AC. BTW, its the manual type not climate control.

Anyway, when I turn it on and set it to. say, number 4 it blows out very hard. Then without chaning the setting it seems to slow down.

Sometimes then a few minutes later, it'll go back into turbo mode again.

Is it supposed to do this? Why?

 

[jimmy]

Mine does the same, I think it is more than manual and not quite full climate control. MB call it automatic airconditioning, it appears to work the same as climate control without the digital display.

If you leave the temp dials half way it will blow warm air until the interior heats up and then will blower cooler air, later in the day it blow really cold air as needed, just like climate control.

The fan also adjusts speed accordingly. I thought it was a fault too, but I dont know why the fan goes into 'turbo' mode on its own occasionally, mine does too so if both ours cars do it, it must be supposed to do it.

 

[paulfoel]

Ah. So its not a fault then...

 

[Steve_Perry]

The a/c control unit, modular block with the dials and buttons that sits behind the dash, can go wrong. I had a fault with mine when I first got the car but got it replaced under warranty. However, my symptoms were different from the ones that you describe, the a/c fans would blow at full tilt and full heat no matter what tune you'd play on the dials.

S.

 

[sym]

mine does it too - must be standard - quite neat really . . . . "semi" climate control.

S.

 

[Andy W]

I think that it is called chaos cool, the system responds to what the temperature probe in the cooling matrix demands at that given time.

 

[Gizmo750]

Just to add to your sense that nothing is wrong mine does it too and the dealer described it to me exactly as Sym put it - "semi" climate control.

I went and asked as I wondered too and my dealer is used to me asking stupid questions

 

[GrahamC230K]

So I set my temp dials so the white bit is dead centre then have my fan on a highish speed and after a while it will vary speed on it's own??

Let me know if I have correct I shall try on way home. Never noticed before though.

 

[sym]

it seems to works regardless of the position of my temp dials.

Had mine set on max cool, with fan speed at 3.5 - and it was on and off to maintain the coolness today - no lack of coolness when the fan speed dropped though, so it definitely works.

S.

 

[GrahamC230K]

What years are your cars?

I have never noticed this and mine is a 1999 Car.

The speed I set stays constant unless I change it.

Mind due Sym, you have the later single electric engine cooling fan whilst I don't and your are on a S plate and me on a T.

 

[sym]

nope - mine is a T - May 99 .... the S is just for show !

S.

 

[Steve_Perry]

My experience is similar to Grahams, if I set a fan speed it sticks to that speed. However, I usually keep the temp dials in extreme blue rather than the white setting. I have tested the fan speed from 0 to 5 and you can tell from the fan noise that each setting and half setting increments the rpm, I've never noticed it change it by itself though. I'll have to pay more attention


S.

 

[Simon]

My fan alters speed on its own also. There’s a little fan assisted sensor near the rear view mirror that samples the temperature inside the car. This must be what governs the whole thing.

 

[jimmy]

My 99/T C180 did not do it (that I noticed) but I noticed it straight away on my 98/R C250.

Perhaps the later cars dont have such luxuries!!

 

[Aletank]

What years are your cars?
I have never noticed this and mine is a 1999 Car

Yep mine's a 1/3/99 T reg , I've noticed it too on mine.
I've had the Air Con on the coldest and the fan on pretty high and after a while the fan speed slows down sort of like its dropped down a setting by itself.

 

[GrahamC230K]

Having the temp dial set to the white does vary the output temperature, but my fan does not vary on it's own.

This is the case for my 88/R C200 and 99/T C230K.

 

[fuzzer]

Move it from the white to the blue and listen to the fan change.

 

[GrahamC230K]

Originally posted by fuzzer
Move it from the white to the blue and listen to the fan change.

Nah, no change.


OK grasping at straws now, anyone got a Sport trim w202 that does this?

 

[Aletank]

OK grasping at straws now, anyone got a Sport trim w202 that does this?

Yep mine does it - 1/3/99 C200 Sport

 

[fuzzer]

ive had 2 202's with AC and our T210 does the same.

Hmm , weird