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Hello,
I have the parts from the rear heater out of a W220. duo-valve, heater/ac/fan unit, and controller.
here are the parts i need help with.
Mercedes says it will not release any electrical info.
duo-valve heater unit part number heater unit heater head unit heater head unit part number
I need to know the wiring for the duo-valve, and the secondary plug on the head unit (white connector). This is going into a custom car project, not into a mercedes.
I know that red is batt+ 12v, and brown is ground. but thats it beyond that.
Help?
Last edited by ydeardorff; Jul 8, 2017 at 02:35 PM.
The connector near the twin solenoids controls the engine coolant flow to the left and right heat exchangers (heater cores). The HVAC computer controls Pulse Width Modulated current to the solenoids to pulse them closed. With no power applied, the valves are wide open. With continuous power applied (not actually the usual mode of operation) the valves will be fully closed. When the ground terminal is pulsed by the computer, the valves will pass the amount of coolant needed to control the temperature of the output air from the heat exchangers. Full 12vdc power is applied to the center pin in the connector. The two outer pins have individual PWM ground applied to control the solenoids.
If the hoses aren't clearly marked, you can determine the pairs by powering a solenoid and seeing which pair of hoses is now blocked, Remove power, and that pair should have full free flow. Mark those two as a pair, mark the other two as the other pair. A pair has hot coolant in on one hose, controlled coolant out on the other hose. Two pairs, two heat exchangers controlled.
The single round device is an electric coolant pump. It pumps extra/supplemental coolant for REST, the Residual Heat system that will keep the interior warm for a brief time while parked, and also when the engine is at idle, and the coolant flow is insufficient to maintain full interior heating. The pin nearest the flat side of the connector is positive (12vdc), the one nearest the round side is ground.
You should disassemble, clean and check the solenoid valves, as they get sticky or dirty. Be certain that you see the very small coil springs on each valve stem, and make sure that they are properly reinstalled during assembly. To reassemble, lubricate the small screws. Reinstall each of the screws by placing them in the hole, pressing down with a screwdriver as you turn the screws slowly counter-clockwise (lefty-loosey) until you feel the screw drop slightly Immediately stop and turn the screws clockwise (righty-tighty) so as to start the screw threads into the threads that they cut on initial installation. If you don't do this, you stand a good chance of breaking the little screws.
Take the pump motor off and make sure that the magnetic-coupling cup on the end rotates freely. Applying 12vdc to the pins (polarity given above) should make the pump motor spin smoothly and quietly. Install the retaining screws using the same procedure described above.
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