A/C Malfunction BackSeat Unit
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 470
Likes: 3
From: McLean, VA
2003 E500 Benz & 2015 BMW M235ix
A/C Malfunction BackSeat Unit
Anyone had this problem and know the fix: I was driving on a 100 mile trip a couple days ago with the A/C System working fine but after about 30 minutes the backseat unit started pumping out very hot air. I put the temp down to lowest setting but to no avail. We made a 10 minute rest stop at the 50 mile point and restart the vehicle and it started pumping out cold air in the back. It was o.k. for another 10-15 minutes and then once again start pumping out very hot air just in the backseat unit. After we got to the hotel and drove to a restaurant that evening, it was o.k. again. But on the return trip, it did the same patern for the first half the trip, but after a rest stop again, restart car and it was o.k. It hasn't done this since. I'll have it checked out when I go in for my A service next month, but wondered if anyone knows what's the problem?
MBWorld Fanatic!
Joined: Mar 2004
Posts: 5,017
Likes: 16
From: Ft. Lauderdale Area, USA
2015 ML 350
It is a very well known problem with these cars. I first experienced it on my '04. The problem is a bad Hot Water "diverter Valve" thingy located under the cowl on the Drivers side. Some guys have replace it themselves, others has the dealer fix it. There is a "How To" posted here too.
Fix it. The car can become unbearable in the Summer Heat when this happens randomly.
https://mbworld.org/forums/e-class-w...rol-valve.html
Fix it. The car can become unbearable in the Summer Heat when this happens randomly.
https://mbworld.org/forums/e-class-w...rol-valve.html
Senior Member
Joined: Dec 2003
Posts: 258
Likes: 1
From: Jacksonville
2013 SLK
Mine just did this a couple weeks ago, its a common fault. And fairly easy to fix. Its the heater control valve. Cost is about $60 if your do it yourself. Do a search, there is a great DIY post.
JM
JM
Member
Joined: Mar 2009
Posts: 97
Likes: 0
From: Connecticut
2007 E550 4-Matic
I actually had a similar problem once that the front unit temp did not correspond to the back unit. I had the A/C on but the back was set to heat. Not sure what I did but it seems to have fix itself.
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 470
Likes: 3
From: McLean, VA
2003 E500 Benz & 2015 BMW M235ix
It is a very well known problem with these cars. I first experienced it on my '04. The problem is a bad Hot Water "diverter Valve" thingy located under the cowl on the Drivers side. Some guys have replace it themselves, others has the dealer fix it. There is a "How To" posted here too.
Fix it. The car can become unbearable in the Summer Heat when this happens randomly.
https://mbworld.org/forums/e-class-w...rol-valve.html
Fix it. The car can become unbearable in the Summer Heat when this happens randomly.
https://mbworld.org/forums/e-class-w...rol-valve.html
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 470
Likes: 3
From: McLean, VA
2003 E500 Benz & 2015 BMW M235ix
Wondering how your 03 E500 is holding up........how many miles on it too? Mine is doing fine except for the radiator/transmission problem a couple years ago at 40k miles and other wear & tear stuff, like this A/C issue.
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Thread Starter
Senior Member
Joined: Oct 2006
Posts: 470
Likes: 3
From: McLean, VA
2003 E500 Benz & 2015 BMW M235ix
I plan to get a third party warranty after my MB CPO Extended Warranty expires in Jan 2010. If your warranty is from a third party, which one do you use?
MBWorld Fanatic!
Joined: Mar 2006
Posts: 3,254
Likes: 15
From: Louisiana
03 E500 and Corvette
Given the issues you have had watch for:
squeeks in the front ... ball joints
Suspension................. Struts or Air springs
Brake warning stop now. SBC failure
These are just a few of the failures I had after 45,000 miles. Still holding my breath for the next failure.
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 470
Likes: 3
From: McLean, VA
2003 E500 Benz & 2015 BMW M235ix
My vehicle is in for the B Service and I asked them to fix the problem with very hot air coming from the backseat unit when the A/C unit is operating. Since it was working o.k. when they checked it out, they at first said they couldn't replace the heater control valve under my CPO warranty and I'd have to bring it in when it was acting up to verify the problem. But shortly later they called me back to indicate they had found a "stored" fault code in the computer about the problem and that was sufficient evidence to then do the repair under the warranty. Thank goodness for storing fault codes in these vehicle computers!
MBWorld Fanatic!
Joined: Mar 2004
Posts: 5,017
Likes: 16
From: Ft. Lauderdale Area, USA
2015 ML 350
My vehicle is in for the B Service and I asked them to fix the problem with very hot air coming from the backseat unit when the A/C unit is operating. Since it was working o.k. when they checked it out, they at first said they couldn't replace the heater control valve under my CPO warranty and I'd have to bring it in when it was acting up to verify the problem. But shortly later they called me back to indicate they had found a "stored" fault code in the computer about the problem and that was sufficient evidence to then do the repair under the warranty. Thank goodness for storing fault codes in these vehicle computers!
Thread Starter
Senior Member
Joined: Oct 2006
Posts: 470
Likes: 3
From: McLean, VA
2003 E500 Benz & 2015 BMW M235ix
Kind of stupid on your dealer's part... you'd never know about this kind of problem unless you experienced it.... and dealers know exactly what the fix is. It occurs randomly and can ruin your enjoyment of the car. If you complained about it, you have it. Period. Stupid Dealer.
Newbie
Joined: Apr 2007
Posts: 6
Likes: 0
From: Staten Island, NY
2003 E500
I had the same issue 3 weeks ago and did the same thing.. did not turn my car off so they can see the problem. The first time they said "you didn't have the A/C button on". It turned out that the rear shut off valve was stuck in the open position which would then make it blow hot air... I have not had an issue since then.
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Joined: Dec 2006
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From: Europe
223.168 & 213.012 & 906.633 & 214.005
