Rear A/C blowing hot from left and cold from low.DIY Changeover valve
Thread Starter
Super Member
Joined: Dec 2005
Posts: 806
Likes: 27
From: Rochester, NY
2009 S550 AMG sport pckg. 2014 Ford F-150 Lariat Supercrewcab
Rear A/C blowing hot one side, cold another. DIY heater control valve (Duovalve)
I've had a lull of DIY posts and now I got a new one. When my nephew put the A/C on in the rear the other day it was half hot, half cold. Checked the setting and all was good. Common issue is the changeover valve. Gonna do a DIY on it and let you know if it works. 60 bucks at the dealer.
Last edited by Nickthegreek; Jul 25, 2015 at 07:21 PM.
Thread Starter
Super Member
Joined: Dec 2005
Posts: 806
Likes: 27
From: Rochester, NY
2009 S550 AMG sport pckg. 2014 Ford F-150 Lariat Supercrewcab
Ok so I made a bad... it's called the duovalve and it sits behind the passender side fender liner. What I bought was a heater control valve. And of course the duo valve is 394 bucks...
Last edited by Nickthegreek; Jul 23, 2015 at 11:02 PM.
Thread Starter
Super Member
Joined: Dec 2005
Posts: 806
Likes: 27
From: Rochester, NY
2009 S550 AMG sport pckg. 2014 Ford F-150 Lariat Supercrewcab
Just as another update I confirmed that it is definitely the duovalve by testing it on sds. On the right if I opened the valve it went hot then if I closed it it went back to cold. The left side just remained hot which makes me suspect it that much more. If it does not solve it then I would say the blend door is the culprit... well see monday
Thread Starter
Super Member
Joined: Dec 2005
Posts: 806
Likes: 27
From: Rochester, NY
2009 S550 AMG sport pckg. 2014 Ford F-150 Lariat Supercrewcab
Replaced the duovalve and voila. A/C is working in the back again. Not a hard job at all. The only thing that caught me by surprise is it dumped a lot of antifreeze. So have a catch pan ready. Prolly about 2 or 3 liters. Other than that is was simple. The way it works is there's a pintle that is activated by a solenoid. I'm betting that because of the heat and corrosion, the solenoid gives and doesn't close the pintle, which usually would block hot coolant from coming into the rear heater core. Before the center console would get hot and I noticed the center knob was almost scalding hot. I tried taking it apart to see if I could fix it but the bolts just sheared right off because they were corroded so bad, so no point in trying to fix it. Just replace. Not cheap
Tools needed
10mm socket
pliers
jackstands
Jacks
17mm socket or 17mm facomm socket
Catch pan
Screwdriver
Tools needed
10mm socket
pliers
jackstands
Jacks
17mm socket or 17mm facomm socket
Catch pan
Screwdriver
Last edited by Nickthegreek; Jul 27, 2015 at 11:39 PM.
