Aircon problem?

[Parrot of Doom]

Just the other day I was driving down the motorway with the aircon on, no problems. Pulled into the services for a coffee, and setting off again the aircon started blowing roasting hot air into the cabin for a minute or so. Then it went cold again.

Its done this twice this week. Any idea what the problem is? Moving the dials/switches/temp dials makes no difference to the temperature until it goes cold again

 

[Sprint'n'Go]

I seem to remember something about this from an article I once read.

As moisture naturaly creeps into the refrigerant over time it eventually reaches a level where it can form lumps of ice somewhere in the system (I think at the entry point to the evaporator?). This then causes erratic operation as the ice forms then melts then refreezes in a continuous cycle.

If this is the problem then a regas with a new dryer should cure it, but then someone else may know of a different reason.

 

[jberks]

Perhaps I'm misunderstanding. The aircon will take a short while to kick in. I get roasting air from mine (and its basically new) for the best part of a minute. It would be quicker if it was straight out onto a 60 mph road, but the compressor is engine rev dependent and creeping out of a car park and down the 15mph exit roads, it can take a short while to cool everything down again.

 

[Parrot of Doom]

But you'll get roasting air from the car when its been sat in the sun for a few hours, and the engine is still cold?

The trouble with mine was that the engine was quite warm, and just a minute before lovely chilled air was coming out the vents. It just seemed as though the temperature dials were set full on red?

If theres a problem with moisture in the system then I guess a re-gas would cure that? At 9 years old I guess it could do with being changed.

 

[jberks]

Depends how long its been sat. If the ambient temp is 24 or so, then it won't take long for the interior, all the vent pipes and the aircon system itself to warm up to oven temps. Then Blast 24 degree air through and you get baked until the compressor can catch up and cool the whole thing down again. If I went out now, mine would be blasting hot air out until I left the car park and got out onto the main roads. In fact, I tend to turn the fan down for a minute (leave the aircon on though) and open the window.

That said, the aircon systems do 'slow down' over time. I started to notice mine wasn't as enthusiastic as it had been after 6 years. Still worked well enough (like yours) just took a little longer to get there. So, yes, I suspect a recharge may work wonders.

 

[Parrot of Doom]

Today it did it again. I'd driven about 15 miles and parked up for 10 minutes. Then I drove away, and instantly roasting hot air started coming through the vents. It showed no sign of going away. Anyhow I parked up later, and a few hours later the car was fine again.

Now it appears to only be doing this through the driver's side vents - the passenger vents appear to be nice and cool, and blowing at the same speed.

Direction, fan and temperature dials make no difference to the temperature of this hot air. I'm thinking that something to do with the driver's side temperature dial has broken, or possibly a dry joint?

Can anybody tell me first how I remove the fascia board for the heater, and second are there any modules/boxes/boards that I should pay attention to? I'm experienced with a soldering iron. I don't think its a dirty temperature dial but I will spray them with contact cleaner anyway.

 

[angus falconer]

Just the other day I was driving down the motorway with the aircon on, no problems. Pulled into the services for a coffee, and setting off again the aircon started blowing roasting hot air into the cabin for a minute or so. Then it went cold again.

Its done this twice this week. Any idea what the problem is? Moving the dials/switches/temp dials makes no difference to the temperature until it goes cold again

Try re-charging the gas - it it is low (and you have Climate) the sensorscan apparently get confused. Mine kept lowing hot and cold till I had it recharged

 

[Blobcat]

Try re-charging the gas - it it is low (and you have Climate) the sensorscan apparently get confused. Mine kept lowing hot and cold till I had it recharged

Agree with regassing. The AC specialist I usd recommended 210's to be gassed ever 12-24 months as they do leak. Mine is great again since it was done.

 

[Parrot of Doom]

But why would it blow cold on one side, and hot on the other?

 

[television]

A good tell tale is that if the air con works on an average temp day, but does not work when the temp goes over 23-25c then re charging is the answer.

Malcolm

 

[Parrot of Doom]

Hmmm, it does seem to happen on hot days. The first day it happened was IIRC a very nice hot day.

Still puzzles me as to why it only goes mad on the driver's side....

Is there a sound AC specialist around Manchester, one who knows about Mercs and whom I can trust to advise me correctly on any dodgy seals, leaks etc?

 

[television]

Hmmm, it does seem to happen on hot days. The first day it happened was IIRC a very nice hot day.

Still puzzles me as to why it only goes mad on the driver's side....

Is there a sound AC specialist around Manchester, one who knows about Mercs and whom I can trust to advise me correctly on any dodgy seals, leaks etc?

These guys can test to see if the presure is up, are not most of your heating controls vacuam operated.

Malcolm

 

[Parrot of Doom]

Not sure, they're certainly manual in operation.

Occasionally something 'switches' on the system and theres a loud rushing of air near the glovebox, I have no idea what its doing though.

 

[television]

Not sure, they're certainly manual in operation.

Occasionally something 'switches' on the system and theres a loud rushing of air near the glovebox, I have no idea what its doing though.

could be the air trying to come out,but a flap is stuck, let me have the first 6 numbers of VIN and I will look up all heater faults for you tomorrow.

Malcolm

 

[Parrot of Doom]

Thanks Malcolm:

WDB2100252....

 

[jberks]

Now it appears to only be doing this through the driver's side vents - the passenger vents appear to be nice and cool, and blowing at the same speed.

Both temp controls set to the same setting and one side hot, the other cold = duovalve I would have thought.
It's possible both sides are playing up, hence you get both sometimes too.
When duovalves are unpowered, do they open? If so, it would explain why it tends to happen after parking - power comes on but they don't close immediately.

 

[jberks]

Occasionally something 'switches' on the system and theres a loud rushing of air near the glovebox, I have no idea what its doing though.

My 210 used to do this too. Quite normal. I suspect it was running in recirc mode until the temp dropped enough and then switch over to fresh again. Just a theory but it only seemed to happen when the interior was baking.

 

[Blobcat]

Occasionally something 'switches' on the system and theres a loud rushing of air near the glovebox, I have no idea what its doing though.

Everytime my 210 has made the loud rushing of air sound near the glovebox with AC set to full cold the system has been out of gas. It is another sign I've found which denotes no gas.

 

[Parrot of Doom]

Hmm, that makes sense - if the system automatically switches to recirculate to cool the interior of the car more quickly, that suggests that its struggling to cool the car.

Theres a place near me that does AC, I'll get it looked at and report back.

 

[jberks]

Hmm, that makes sense - if the system automatically switches to recirculate to cool the interior of the car more quickly, that suggests that its struggling to cool the car.

Not necessarily - it will always take a min or so for the aircon to get fully cold. The it's going to take another 5 mins or so to drop the interior temp, even at full pelt. If you find it suddenly quietens down after a few mins, rather like a flap closing, I reckon that's perfectly normal. Mine did this from new and the aircon worked fine. In any case, low pressure and it won't come on in the first place.

Even on my 211, where aircon is 100%, it's really frustrating when I get in the car on a warm day like today. The fan fires up full blast on the climate, but for the first min or so it only has hot air to dispense, especially when the engine revs are low as I creep out of the car park. I generally turn off the climate until I've done half a mile or so at 30+ and the aircon has had chance to cool down.

If your aircon gets cold, ever, it's probably ok, but your side/side issue is curious. The only aspect I know that is side related is the duovalve and if the duovalve is pumping hot water into the driver's side and occasionally passenger side matrix, no matter how efficient your aircon, you'll get warm air.