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  #16  
Old 03-02-2008, 07:26 PM
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more duovalve info

While waiting for the correct thermostat to arrive, I took apart the duovalve.

Closer inspection of the device reveals that the inside of the coil assembly is designed to be wet with coolant. There are rubber gaskets that create a seal between the base of the coil spool and the valve housing, as well as the top of the coil spool and the metal can that covers it. These seals keep the windings dry, but the metal rod inside is bathed in coolant. I'm guessing this was done so that the metal rod could move up and down freely, without having to pass through some sort of sliding seal. The metal rod actually has a hole all the way through the center of it, allowing the coolant to fill the inside of the spool.

Everything inside the valve appeared to be pristine; no build-up or corrosion to clean. However, the metal rod did have a tendency to bind up sometime when I actuated it by hand. It didn't really slide too freely and I can understand why it might get bound up occasionally and cause the heater to malfunction. I can't think of any type of grease that could lubricate the valve with hot coolant constantly flushing it.

Do you thing a water pump lubricant additive would help? Can you recommend any that are compatible with the MB coolant?

Thanks,
Paul

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  #17  
Old 03-07-2008, 07:38 PM
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duo

"Closer inspection of the device reveals that the inside of the coil assembly is designed to be wet with coolant."

NO!.. that is not true....
The valve is defective it must be replaced.
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  #18  
Old 03-08-2008, 04:30 PM
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Quote:
Originally Posted by Anthony Cerami View Post
"Closer inspection of the device reveals that the inside of the coil assembly is designed to be wet with coolant."

NO!.. that is not true....
The valve is defective it must be replaced.
Hi Anthony,

It's tough to describe with words what areas the coolant has access to within the duovalve. Take a look at the attached photos to see where I mean.

Paul
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98 E300D W210 Climate control problem-duovalve-102k.jpg  
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  #19  
Old 03-08-2008, 04:39 PM
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Thermostat update

I was able to get the correct thermostat from Fastlane and get the car back together. Now the temp gauge on the dash reads 80 deg C and the air blowing out of the side vents on high heat reaches 130+ F. I'd say that the heating system is now working as to be expected.

The Duovalve seems to be operating properly. The vent temp decreases from 130F if I reduce the setpoint temp of the climate control, suggesting that the duovalve is modulating the flow of hot coolant to the heater core. Of course the real test will be this summer when I run the AC. Hopefully the occasional blasts of hot air that I previously experienced will not reoccur.

Thanks for all your help,
Paul
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  #20  
Old 03-08-2008, 09:36 PM
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Good to hear you got it working Paul.

One thing you can do to verify the duo-valve operation is to set the driver's side temp to something like 65 deg., get under the hood and grasp the driver's side solenoid and note the rate at which is clicks. You can then ramp up the temp to 80 something and again grasp the solenoid and you should observe an increase in the click rate. Repeat the test for the passenger's side as they work independantly. Also be careful not to grab the solenoids when the engine is fully warmed up as they get hot as fire.
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  #21  
Old 03-08-2008, 09:50 PM
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Listening with a stethoscope would do just as well, and won't burn you. If you don't own a stethoscope yet, you can put a screwdriver tip against the part, and put the handle to your ear.
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  #22  
Old 03-12-2008, 11:12 PM
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Hi Evan,

The solenoids seem to be working properly- the electrical parts actuate and must in turn be opening and closing the valves because the air temp coming out of the vents does in fact drop when the setpoint is lowered. All is good - just in time for spring!

Also, it was important that I fixed the low coolant temp problem since I depend upon hot coolant to pre-heat my veggie oil before it gets to the filter. I feel good about the 80 degC that I get now. The 65C that I was seeing before was worrying me a little because my fuel wasn't reaching the desired temp.

Thanks for everyone's help!
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  #23  
Old 11-28-2008, 09:21 PM
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7 months later... Duovalve update

Just wanted to complete this thread by reporting that my duovalve performed properly while using my AC this summer. The cleaning that I did back in March seems to have done the trick to prevent the valves from sticking open and heating my air-conditioned air.

Paul

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