Air conditioning sometimes goes off on 190E after 5 - 10 mins

[phil_2413]

I have a 1993 190E 2.0 petrol which has an intermittant problem with the air conditioning.

Sometimes when I have been driving for 5 - 10 minutes the AC stops blowing cold air. It feels like some very mildly chilled air is still coming out of the side vents (but definately not the centre vents), but nothing like it should. Turning the AC on and off doesn't help but if you stop the engine and re-start it the AC works fine again every time. When it works it blows ice cold.

It doesn't do this all the time, just every now and again but often enough to be annoying. The car has just had a new poly-v belt and tensioner fitted and the belt isn't slipping as I can see, but it had this problem before that work was done.

The garage tell me they have changed the AC thermostat switch but this doesn't seem to have helped. It was also re-gassed, and there are no leaks I am aware of.

Can anyone please suggest what it might be before I consider taking it to a specialist?

Thank you in advance for any advice you can give!

Regards,
Phil.

 

[television]

Hello and welcome.

Not easy with air con faults as they are specialist things.

On your car the clutch engages to start the compressor, if the clutch is not cutting in,it must be a sensor or poor a bad connection in the control unit, and these control unit can get dirty switch contacts that can be cleaned

 

[phil_2413]

Hi Malcolm

Thank you, I have never used a forum of any kind before so it's nice to get a reply. Reading other peoples' posts has helped a great deal with various things in the past.

Do you know where the AC control unit is please, is it part of the compressor, or behind the dashboard somewhere? Also is the clutch in the compressor or separate?

I think it will have to go to the specialist if it keeps doing it, but I'd like to be armed with as much knowledge as possible for when I go.

Thanks again,

Phil.

 

[television]

These are a few links as to where things are
control
http://www.detali.ru/cat/oem_mb2.as...&L=765.902&CT=F&cat=500&SID=83&SGR=150&SGN=03

Air con lines

http://www.detali.ru/cat/oem_mb2.as...&L=765.902&CT=F&cat=500&SID=83&SGR=195&SGN=06

Blower case
http://www.detali.ru/cat/oem_mb2.as...&L=765.902&CT=F&cat=500&SID=83&SGR=045&SGN=01

Air guide
http://www.detali.ru/cat/oem_mb2.as...&L=765.902&CT=F&cat=500&SID=83&SGR=165&SGN=04


Sorry that we cannot do better on this your first visit, but please take part in the forum

 

[bigasotonuk]

Hi,
I,m no expert on A/C, but having investigated problems with climate control issues with my C43, it sounds like cabin temp sensor, or Evap sensor to me, this is providing the compressor is still running when the temp changes. Regarding the thermostat that has been changed already it sounds like one of the sensors i have mentioned above has been changed already, I would intially change the other.

 

[phil_2413]

Thanks for that guys, it's useful to be able to direct them to check these points before they try to replace the whole compressor when it might just be something simple.

Thanks also for the diagrams, will print them off and take them along to the garage when I go along.

Phil.

 

[phil_2413]

Quick update, it's stopped going off (for now!) but sometimes I've noticed the engine hunts at idle and the RPM momentarily drops quite low which I think might be disengaging the AC compressor clutch (hence why re-starting the engine makes the AC work again).

Looking at some other posts looks like I need to look at the vacuum pipes for a possible leak.

 

[Pontoneer]

On the W201 , the centre vent is just a fresh air vent - it certainly does not put out hot air and I doubt it would put out chilled air either ( though I haven't seen a 190 with air-con as they're pretty rare in the UK ) .

 

[phil_2413]

On the W201 , the centre vent is just a fresh air vent - it certainly does not put out hot air and I doubt it would put out chilled air either ( though I haven't seen a 190 with air-con as they're pretty rare in the UK ) .

Thanks for the info Derek, cold air does seem to come out of the centre vents but looking at the car they seem to have made some changes for the hot climates, for example the heater matrix is blocked off by a cap that looks like was fitted from new so no water flows through it. A mechanic told me this was done by MB to make the AC work better but on a chilly winter's night I am assuming you'd better have a jacket as I would imagine the heater is of no use!

Part of the mystery though is when the AC goes off why some cold air still comes out from the side vents, just not nowhere near enough to keep the car cool. Will ask a specialist to take a look.

 

[Phil469]

same issues

Hey Phil,

Did you ever figure out what was causing your A/C issues. I have a 1985 190e and it's doing exactly the same thing yours was. Cutting off sometimes and at idle, the drop in RPMs and then re-surging back up.

Let me know if you can.

Thanks,

phil