TSommerville

Hi Guys and Girls,

I've got an ML320CDI W164 with a bit of a weird issue and I was wondering if anyone had some clue as to where to head with this.

After about an hours driving with the a/c on, all the vents seem to close and there is no air coming out of any of the vents. It's like the blower flaps and actuators in the HVAC have all turned into the closed position. I've got no idea why this might be happening and it doesn't matter whether it is set on auto or I manually select the vent setting. It does, however, correct itself if I turn the car off and then on again after about a 15 minute break.

Getting kind of warm around here these days and I'd like to be able to head on long trips without the stress of basically having no A/C for the duration.

Any help would be appreciated

ItalianJoe1

Sounds more like the blower motor or resistor is dying out, take it and have it checked out?

TSommerville

Yeah I forgot to mention, you can actually hear the fan (blower motor) still working. Especially if you select the high fan setting. Its just there is no air coming out of any of the vents.

ItalianJoe1

If the fan is spinning it has to go somewhere, is it going to the defroster vents?

I'd suggest starting with an update of the AAC, it sounds like there's some sort of bad data or software corruption causing it to see something and lock up, but re-set after being off long enough.The control panels do act up from time to time, often a software update/reset will fix them, but it may need to be replaced. Have it scanned, there are probably faults in there.

Shadow5501

It sounds like your evaporator is icing up and blocking airflow out of the vents. When you stop the ice melts and all is fine again - for a while. As a temporary fix you can switch off the aircon compressor when airflow starts to decrease - the ice will melt, airflow will increase and start to warm up. There are a couple possible causes of evap icing, the most common being slightly low refrigerant level.

Maj. Dundee

Codes must be read which stored in the AAC Control Module. Look at all the possibilities.

TSommerville

Loving the ideas guys. I'd say it definitely seems like finding someone with a Star Diagnostics will be my next step!

I'll keep you posted on progress !

Thanks again

Maj. Dundee

Star would be great, but you can buy your own scanner which can read every module. This one will do it./

TSommerville

Just a bit of a conclusion on this one.

Had it over to the shop today and he says some bodgy fool has wired up the AC compressor so that it runs at 100% capacity the whole time the car is running.

Once he removed the wire he then found that the climate control panel was not working and needs to be replaced.

Not cheap but thankfully I'll have proper working aircon soon enough!

Maj. Dundee

Did he show you this wire that someone used to jump the compressor?

TSommerville

So these are the pictures of the jumper wire. Still haven’t gotten the new module because he wanted almost $1800 for it. Ebay’d the part and you can get them for under $500. Even found a mob in Brookvale who say they can recondition them.

Maj. Dundee

Did you recently buy this car?

What I am thinking is that the previous owner tried to correct the problem you are now having and you wound up with his brain child.

Obviously one end of the jumper wire is attached to the compressor, but do you know where the other end is attached to?

In the first photo that you posted was that the way you or the mech. found it?

Please UPDATE YOUR PROFILE in USER CP the year and where you live.

TSommerville

Yeah I've only had this car a few weeks.

The other end of that wire that isn't in the engine bay is behind the climate control panel and connects into a wire coming out of one of the multi plugs that go straight into the module.

Am sorely tempted to just take that wire out completely and then get it looked at in stock standard form.

Maj. Dundee

It would help greatly if you removed the AAC Control module and see what color wire the jumper is attached to.

Also, are you sure that the jumper wire is attached to the compressor wire?

TSommerville

It is connected to a green wire with a white trace into the back of the module then it goes through the firewall and connects to that green wire with the blue trace.

Havent actually looked at the back of the compressor or traced the wire any further so I’m not 100% sure.

If if anyone has a wiring diagram of the car I’m sure that would answer any questions as to what was actually being done here.

Maj. Dundee

Post your full vin# and I will post it on the forum.

TSommerville

WDC1641222A102074

Maj. Dundee

Here is the wiring diagram and the legend. A9 is the compressor. N22 is the AAC Module and note that it is powered by fuse #12 in the cockpit fuse box on the side of the Instrument Panel. So check that fuse first. You must cut and attach the sheets together.

Also included is a copy of your DATA sheet.

TSommerville

Hi Guys,

Sorry to be dragging up such an old post but just incase anyone was interested in the resolution to this. I had it over to a workshop with a proper auto electrician and it turns out the Diode in the control valve on the back of the compressor was burnt out, so he placed another one in line on the ground wire from the valve and voila! The AC is working perfectly again.

Maj. Dundee

I don't understand about this diode being installed inline with the ground wire. There is no GROUND wire. Ground for the compressor is obtained by attaching the compressor to the eng.