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ML320 air-con prob

Posted: Wed 05 Oct, 2011 11:29 pm
by debgreen
Hi I'm new here so hope someone can help. I'm not much of a car person, so please be patient.
I have an ML320 CDI 4matic 2009 model.
Last summer the air-con started switching itself off on hot days, while I was driving. The lights on the dashboard go out and then there is a huge noise of fans switching on under the bonnet, as if there's a jet engine under there, while I'm still driving. And the air-con outlets pump boiling hot air, it's like having the heater on full blast. It's really freaky. And hot.

Over winter, it hardly ever happened. Now it's getting warmer again, it's doing it more often, so maybe it's triggered by the thermostat reaching, say 25 degrees or something. My duaghter was driving today and it happened again, and while she was driving along the indicator on the dash said that the temperature of the car was +85 degrees celsius!!!! She was so shocked she said she wished she took a photo of it.

Then, if you keep driving, for no apparent reason at all, it will switch itself back on again, and nice cool air will come out. But you never know when it's going to happen.
It happens several times a day, and I spend about 4 hours each day on the road so it's very uncomfortable even in mildly warm weather, let alone a hot day.

The only way to fix the problem is to whack it HARD with the side of my fist, either on the left or right side of the vertical console. So maybe it's a loose wire or something. This is what got me through last summer, me driving my beautiful car around Sydney, and THUMP, yep, that's got the air-con working, YAY! Must've looked like an idiot.

The dealer workshop has inspected it twice/three times and says there's nothing wrong. LOL. Well, I'm worried that the car's going to blow up, or take off into the air, that's what it feels like and sounds like. What are the fans at the front for? They go into really really high revs, and it's really loud and scary especially for my teenage daughter when she's driving alone which she does every night.

Hope someone can help!!! I know it probably sounds funny but maybe this has happened to someone else?
Thanks in advance

Re: ML320 air-con prob

Posted: Thu 06 Oct, 2011 12:16 am
by Ivanerrol
Hi Deb,

I assume that this car is still under warranty?

You need to be very firm with the stealership. If the stealership you bought it from remains uncooperative go to another.
The warranty is covered by Mercedes Benz - not a stealership. If last resort call M.B. head office and complain. They do take notice.

I would place bets on some sensor acting up - or a spurious earthing fault.

Don't let this problem fall over the warranty period. I have first hand experience in a problem with a car that was just out of warranty. :wall:

Re: ML320 air-con prob

Posted: Thu 06 Oct, 2011 9:14 am
by debgreen
Oh dear! Thanks for the heads-up - I had a suspicion they just really couldn't be bothered unscrewing everything and checking all the little bits and pieces, or they ran out of time or whatever. I've had similar probs with a Discovery and its warranty at the Landrover stealership (yes we are a household of 4WDs). There were so many things going wrong with the Disc that the head of the workshop ended up fixing it for free, out of warranty, because he felt sorry for me.
Anyway, back to mercs: If they switched on the air-con in the shop, it would have been fine (derrr).
But as I've never heard of the word "stealership" before, well, I'm obviously very new here LOL.

I'll go back to them and be a drama queen.

I'll also check out that US site, mentioned in another post.

As long as the car doesn't blow up out the back of Woop Woop while my teenage daughter's at the wheel. I suppose it has too many warning systems to do that.
Thanks again!

Re: ML320 air-con prob

Posted: Thu 06 Oct, 2011 1:14 pm
by John Green
As advised go and stand your ground with the dealer. They should be able to spot it by hooking up the diagnostic computor. IMHO many of the guys working on these are either poorly trained or just don't think. Quite often when you read the diagnostic codes there are so many it does not make sense. The correct proceedure when there is a fault that happens quite often is to erase all the codes, drive vehicle until fault occurs and then read codes so all you are seeing is the fault you are looking for.

Fans up the front cool the radiator and the condensor, condensor is part of the A/C system and if the gas over heats the fans should cut in...

Re: ML320 air-con prob

Posted: Thu 06 Oct, 2011 1:35 pm
by Ivanerrol
Land Rovers and Discovery's until they were taken over by B.M.W. used a brand of "British" Electronics.
Lucas - more commonly known as the Price of Darkness.

Lucky you didn't have a mid nineties Range Rover HSE.
The electronics on these were a nightmare.
$7,500 for the wiring loom that controlled the AC (plus install) - Ask me how I know.

Re: ML320 air-con prob

Posted: Thu 06 Oct, 2011 5:47 pm
by Starman
Welcome Deb, great to have you on board.
The hot tip (no pun intended ha ha) is to research your AC issues on ther US Merc forums. They have many more cars in circulation but have the same issues as we do. I recently had an AC problem and the dealer was completely and utterly clueless; when I had them make the fix I found on the US Merc forum then voila, problem solved...!!!
Its benz world dot com, here you go.
This appproach has saved me at least $600 and many hot and bothered days. I swear to god that without the US forum, my problem would stilll not be fixed.