ML320VIC

Hey guys,

I'm really enjoying all the grief this car is giving me ever since I bought it.
Today I'm adding another problem to my long list.

As its summer down here in Australia, and it gets extremely hot, aircon is very important to me. Air con has been working fine since I bought the car, not as ice cold as others I've owned but definitely refrigerated and functioning.
All of a sudden, yesterday, when I'm driving home, I turn on the aircon and push the dial all the way to cold, and wait for it to cool. Waiting, waiting, waiting... Nothing, just warm air.
Toggle the AC button a few times, nope, still warm. Switch the HVAC dial to hot, yep, definitely hot, back to cold, nope, still very very warm. So my first thought is the compressor is dead, I sit at the lights and turn the AC switch off, revs change, then on, I can hear the fan kick in and the revs drop, so seems to be working fine.

Take it home and pop the bonnet, check all fuses, they're all ok, the compressor is engaging fine, the pipes are ice cold, so it's not an issue of lost gas or siezed compressor, but the aircon is blowing almost hot air?

I've been reading threads and the likely culprit seems to be the air blend motor, but I have an older W163 with manual climate control, not proper climate control (I have dials).
My understanding of a bad air blend motor is the temperature won't change regardless of where you turn the dial, but mine is either warm, or if I switch it to hot, it's definitely hot.

Is it definitely my air blend motor? Not a fan of taking things apart only to find out they're ok.

Thanks!

Maj. Dundee

It's either the Blend Door motor or the AC Module N19.

Here is how to check both (you need a DVOM).

https://mbworld.org/forums/m-class-w...ml#post6235472

ML320VIC

youtube.com/fNkPvW7ORMs


I'm unsure what it means. May have had the probes in reverse, but:

@ full hot - 0.6 volts
@ middle - 6.4 volts approx
@ full cold - 6.4-6.8 volts approx

Video is in link above

Any help is appreciated! Thanks

Maj. Dundee

If you conducted the test correctly, then you need N19.

http://www.ebay.com/itm/Mercedes-Benz-Air-Control-ECU-2002-2003-/251013631295?pt=Motors_Car_Truck_Parts_Accessories&hash=item3a71940d3f&vxp=mtr

ML320VIC

I suppose that does make some sense, considering I am having control over medium-hot but nothing below the medium Mark on the dial is actually changing the temp at all (correlates with the fact the voltage changes from white to red between 0-6v but white to blue stays at 6v)

In saying that, I was under the impression that when these things die, they die completely and you lose all control over any heat or cold, but I still am able to control the amount of heat, I just have no cold air at all. Then again it shouldn't be the blend motor slipping because again, I have some control over the amount of heat..

Maj. Dundee

For $39 you should take a shot at it as it is very simple to replace.

Also try and say thank you once and a while.

ML320VIC

Uhh..

And

That's also disregarding the fact that the issue hasn't yet been resolved..

Maj. Dundee

This has nothing to do with the issue being resolved or not. It's about individuals who fail to say anything for free diagrams and instructions and where to buy parts very cheaply. Do you have any idea how much that part costs at M/B? Answer, $190.

And now that you have been supplied with everything you need, you now become arrogant and I become thankless.

ML320VIC

Thankless!!?? I've written it twice mate, what do you want, a red carpet?
You're not going to get a thankyou now. I understand you may be having a bad day but no need to turn into a keyboard warrior.

For the record, that supplier won't ship to Australia, I have to buy the part brand new anyway.

If it concerns you so much, don't reply again. Jesus Christ.

Maj. Dundee

For your record, how is anyone supposed to know where you live? When you joined this forum to get FREE help you never included your location which was asked. But I guess you missed that line because you were too anxious to get that FREE help.

Don't worry mate, you'll never receive another ounce of help from me ever again, Attitude counts and you have a lot of it.

ML320VIC

What is your problem mate??? You've suddenly come here fists swinging as if you're asking for an argument?

and for the sake of again proving that you have not read what I've written and made yourself look like a big a**hole again:

Here's a tip: control + F, and type the word you're looking for, before you post another accusation of apparently something I have not said or made clear.

If you're looking for thanks and praise, jump off the computer, turn it off, leave your house, and go do some charitable work, except don't crack it at those in need when they don't scratch up to your standards of gratefulness, because it makes you look an idiot.

art_arev

A**HOLE helping you & many others for FREE is charitable work, at least show some gratitude!!!!

ML320VIC

Again, are you not reading my posts or is there an unspoken rule here that you must do things in 3s for people to realise you've said something?

ML320VIC

Again, are you not reading my posts or is there an unspoken rule here that you must do things in 3s for people to realise you've said something?

DrX

With disregard for the previous off-topic exchange (which was somewhat uncalled-for), it is quite possible that you need a re-gas. Just because the pipes feel cool doesn't mean the system has enough refrigerant to cool the air. If it's not coming out cold, then you might need more R134.

I researched the problem, and although DIY kits are available overseas, in Australia R134 can only be purchased by licensed refrigeration technicians.

In other words, you need to visit an automotive A/C specialist or your MB dealer. I went with my MB dealer who fixed it for $297 including leak test and free loaner car for the day. (I thought the cost was quite reasonable.)

ML320VIC

Thanks for your reply,
I've ordered the N19 part, but I'll take it to a mate who does R134 regasses this weekend and see if that helps too.
Is it possible for it to be ice cold one day and warm the next?

Thanks

DrX

Before my re-gas, when the ambient temp was cool, sometimes it blew cold, sometimes not. On a hot day, it came out warm. Eventually it was never cold.

After a re-gas, you might be amazed at how cold it can get.

ML320VIC

So I spent $200 on an N19 - didn't work.
$250 on a regas and had to have all the O rings changed on the TX valve. - didn't work.

Mechanic is at a loss. Doesn't think its the blend air door, because when you turn it to full hot, it's really hot. When you turn it to cold, it's about 20C. You can also hear the sound of the fan change and sound deeper on the last 2 clicks of cold, but the air is hotter than 20C if outside is hotter.

He did find that clamping the heater core coolant hoses makes the aircon blow very very cold though, which does sound like the blend air door. But I should have 0 control over temperature.

I'm lost and I'm sick of wasting money on this poor excuse for a car.

LocalGhost

Nope nope nope. Not always the case.

You should have started with the blend air motor actuator, mate. This the very place to start when any problems with hot /cold air problems in these older MLs and practically no-brainer. It can generate any number of symptoms.

My ML was acting exactly the same.
The air blend motors tend to fail mechanically. For example, one of the plastic gears inside is loosing teeth. Mine lost three and wasn't completely closing the hot flap, leaving me with lukewarm air, exactly as yours does.
It was also struggling to go back because of missing teeth, but sometimes it managed to move the flap back to hot position. Result: I had warm air instead of cold and randomly available heat.

$150 for the part at the dealer, 3 hours of work (really easy to remove the top part of dashboard) and my ML is perfectly fine again.

You didn't even try WITHOUT air conditioning on, did you? this would have eliminated the whole AC thing.