ML320 heater blows cold air
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Newbie
Joined: Nov 2007
Posts: 1
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ML-320
ML320 heater blows cold air
My ML320 2002 W163 has been working great till lately; the heater starts to blow normally (hot) then in few seconds switches to worm then cold "outside air". With the chili mornings these days it’s becoming a problem. 
I have already replaced the water pump & the thermostat (3 hr job). I read several posts regarding the BLEND AIR ACTUAROR MOTOR located behind the glove box. I also watched the video from youtube on how to replace it. The motor is operating normally and not clicking.
Is there another area I can check before giving up. Any good advise is appreciated.
I have already replaced the water pump & the thermostat (3 hr job). I read several posts regarding the BLEND AIR ACTUAROR MOTOR located behind the glove box. I also watched the video from youtube on how to replace it. The motor is operating normally and not clicking.Is there another area I can check before giving up. Any good advise is appreciated.
Newbie
Joined: Nov 2013
Posts: 1
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ML320
My heater did not stop after working. I started it up one day and the heat didn't work at all; just blew cold air. I turned the temp dial back and forth a couple of times and the hot air came on. Then the next time I adjusted it to cooler air, the heat never came back. Is this a thermostat thing? I changed the fuse as well as the air filter....
Newbie
Joined: Nov 2013
Posts: 3
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ML320
Hi, I am new to the forum and desperate for some guidance please. I have a 2002 ML320 and have recently noticed that the heater does not work.
I have changed the aux heater pump which now works, both hoses are the same temp so heat is going through the heat exchanger. The dials appear to work and he actuator motor works behind the glove box. The connecting rods seem to be doing their job...
The engine runs at just over 80 degrees celcius so I am totally lost now. Any help would be greatly appreciated. Thank you in advance. Dan
I have changed the aux heater pump which now works, both hoses are the same temp so heat is going through the heat exchanger. The dials appear to work and he actuator motor works behind the glove box. The connecting rods seem to be doing their job...
The engine runs at just over 80 degrees celcius so I am totally lost now. Any help would be greatly appreciated. Thank you in advance. Dan
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Super Member
Joined: May 2013
Posts: 504
Likes: 7
From: Harare, Zimbabwe
2003 ML55,2007 ML63
Firstly check the fuse box & make sure your fuse & the relay is working. Find the relay and exchange it with a similar one from the box for diagnostic purposes. If you dont have heat or AC it must be fuse/relay issue. Temperature control knob moght be the culprit if you have hot but no cold or opposite....
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Super Member
Joined: May 2013
Posts: 504
Likes: 7
From: Harare, Zimbabwe
2003 ML55,2007 ML63
Hi, I am new to the forum and desperate for some guidance please. I have a 2002 ML320 and have recently noticed that the heater does not work.
I have changed the aux heater pump which now works, both hoses are the same temp so heat is going through the heat exchanger. The dials appear to work and he actuator motor works behind the glove box. The connecting rods seem to be doing their job...
The engine runs at just over 80 degrees celcius so I am totally lost now. Any help would be greatly appreciated. Thank you in advance. Dan
I have changed the aux heater pump which now works, both hoses are the same temp so heat is going through the heat exchanger. The dials appear to work and he actuator motor works behind the glove box. The connecting rods seem to be doing their job...
The engine runs at just over 80 degrees celcius so I am totally lost now. Any help would be greatly appreciated. Thank you in advance. Dan
The dials appear to work? Why do you say that? How would you know they work or not? Because you can turn them??
Last edited by art_arev; Dec 12, 2013 at 06:54 PM.
MBWorld Fanatic!
Joined: Oct 2011
Posts: 7,107
Likes: 765
From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
You are on the W163 forum and the only vehicle you have listed is a CLK430. If that is the veh. you are asking about, you are on the wrong forum and we can't help you.
If it's a W163 veh. PLEASE UPDATE YOUR PROFILE in USER CP.
If it's a W163 veh. PLEASE UPDATE YOUR PROFILE in USER CP.
Junior Member
Joined: Dec 2013
Posts: 20
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Clk 430 conv. + ML320
Yes I have both clk 430 and ml320..
My ac and heat in my ml320 is not working, I checked fuses and relays replace temp control unit and still no AC or heat? Hot wire the compressor 12v to verify that new compressor works but with out wire to compressor No ac or heat control. I've check purple wire under fuse box no 12v.? Please help? Need sys to work..
My ac and heat in my ml320 is not working, I checked fuses and relays replace temp control unit and still no AC or heat? Hot wire the compressor 12v to verify that new compressor works but with out wire to compressor No ac or heat control. I've check purple wire under fuse box no 12v.? Please help? Need sys to work..
Super Member
Joined: May 2013
Posts: 504
Likes: 7
From: Harare, Zimbabwe
2003 ML55,2007 ML63
Zan is your blower switch working? There is the dial switch thats switches on and off the blower. And there is a button to switch on the AC. If the fuse /relay is ok & the blower doesnt come on must be the switch. If the switch is ok then you must scan & clear the codes. If there are AC error codes present the blower will not receive 12v unless the codes are cleared.
MBWorld Fanatic!
Joined: Oct 2011
Posts: 7,107
Likes: 765
From: Bronx, N.Y.
2002 ML 320 & 2006 ML500
Junior Member
Joined: Dec 2013
Posts: 20
Likes: 0
Clk 430 conv. + ML320
Zan is your blower switch working? There is the dial switch thats switches on and off the blower. And there is a button to switch on the AC. If the fuse /relay is ok & the blower doesnt come on must be the switch. If the switch is ok then you must scan & clear the codes. If there are AC error codes present the blower will not receive 12v unless the codes are cleared.
Yes blower works and dial works too, and yes there are AC error codes, who can I get to clear them?
Thank you this might be my problem.
Super Member
Joined: May 2013
Posts: 504
Likes: 7
From: Harare, Zimbabwe
2003 ML55,2007 ML63
Junior Member
Joined: Dec 2013
Posts: 20
Likes: 0
Clk 430 conv. + ML320
Thank you again
Newbie
Joined: Nov 2013
Posts: 3
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ML320
You could try removing both inlet and outlet hose from heater matrix licated at bulkhead and using a garden hose, wash out the matrix in the reverse flow to what would be the normal flow of coolant. I had to do this several times before all of the debris cleared. Otherwise, small auxillary pump located near bulk head. These are known to fail but washing out the matrix with a hose wont cost you a penny and is very easy.
