Click here to order! The climate control system on the W210 Chassis Mercedes has a dual climate system. What this means is that one side of the car can be cool, while the other side blows warm air and vice-versa. The Duovalve is used to regulate the amount of engine coolant that flows into the heater core between both sides of the passenger compartment. The Duovalve can fail in a few different ways. The upper electronic portion that holds the coils can develop an internal fault, rendering them inoperative. Usually, there is a break in the coil windings where the wiring meets the electrical connector on the chassis. This is essentially two valves inside a casing that, over time, can become blocked with corrosion from the engine coolant, preventing the valves from closing. In this case, you would get hot air blowing from one or both of the vents at the same time. The Duovalve can also fail when the small pintle shafts break inside the bottom housing. When this happens, the valve can stick open.

Additionally the inside of the two coils can become blocked with corrosion from the engine coolant, preventing the valves from closing. In both cases, you would get hot air blowing from one or both of the vents at the same time. In this article, we will go over the steps involved with disassembling the Duovalve and replacing it, if needed.best time to buy an ac unit Shown here is the Duovalve, which is mounted on the right side of the car, just above the upper mounting point for the front shock.how to know what size ac unit This picture shows the location of the five T15 Torx screws which hold the upper portion of the Duovalve to the lower portion (green arrows).ac window units installation Carefully remove the five screws.

It helps to use a magnetized screwdriver. This will prevent you from dropping the screws under the valve. Retrieving the screws from underneath can be a real pain. Once all the screws are removed, VERY carefully pull the magnetic coils up and off the valve. You'll want to apply equal pressure to each side of the coils. Once free, remove the electrical connector. Sometimes, the inner sealing plate will be stuck inside the coils due to corrosion. What you should see are the two pintle valves inside the bottom half of the Duovalve. In our case, you can see where the shaft of the left valve has broken off (green arrow), leaving the valve cocked in place and the heater blowing hot all the time on one side of the car. In this instance, you will need to replace the whole valve or try to repair the shaft. I've heard of some people using a rivet to repair the shaft and others using high strength epoxy, and then sanding the shaft down. In this picture you can see the inner sealing plate still stuck to the bottom of the Duovalve.

Very carefully pull the two shafts up and out of the plate (green arrows). Make sure that you also retain the springs on the ends of these valves. Once the shafts are removed, carefully apply equal pressure to each side of the plate to remove it (purple arrows). Here is where you want to check for corrosion or any buildup (green arrow). The plunger shaft should be able to move inside the coil with no resistance. Here is the procedure for replacing the entire Duovalve. Begin by clamping off the water hose leading to the Duovalve from the outside of the cowl panel, as shown here. Use a pair of channel locks to loosen and slide back the hose clamp holding the water hose to the Duovalve. Once the hose clamp is off, carefully peel off the water hose and push the grommet molded into the hose out of the cowl panel. Be prepared for a little bit of coolant to spill out of the hose and Duovalve. There are two metal clips on either side of the housing that hold the Duovalve in place (green arrows).

This picture shows the Duovalve removed to give you a better view of the clips. Pull each clip outwards until they stop. Now lift the Duovalve up and out of the housing. It will take a little effort to release it from the bottom. Try to pry it up from the bottom of the Duovalve (yellow arrow), but use caution not to break the lower plastic housing. Press the metal tabs on the housing back inside (green arrows). This prepares the housing to accept the new Duovalve. Shown here are the catches on the Duovalve (green arrows). These slide over the catches in the housing, locking it in place. Now take the new Duovalve and press it down into the housing until both sides click into place. Re-connect the hoses and electrical connectors and you're done. View Cart & CheckOut |  Recommend this page to a friend... []Copyright © Pelican Parts Inc. Registered Agent Contact PageWhat is the Heater Blower Motor Resistor all about? The heater blower motor resistor is located underneath the dashboard in the heater/AC compartment.

The resistor enables the heater blower motor to change the speed of the fan. Without this part you will not be able to change the speed of the airflow from the blower motor. It is also possible that the heater motor blower may not work at all. If the resistor has gone bad, it is likely that the fan will work only on the highest speed. *If no air is coming out of your vents, you may have a problem with the heater blower motor as well as the resistor. * Mechanical resistance to the fan (such as when something gets stuck in the fan), can often cause damage to the heater blower motor resistor. Inspect electrical circuits to verify faulty resistor. Remove and replace the faulty resistor. The air and heating system in your vehicle is a closed system, so it won’t be inspected during servicing and routine maintenance. If you notice any part of the air and heating system behaving bizarrely, however, you should always schedule an inspection. If your fan is stuck on high, you likely have a bad heater blower motor resistor, and should schedule to have it replaced.