Hi,
The car is a W210 E230. The A/C blows cold on the right side and right center vent and warm air on the left and left center vent.
People say it must be the DuoValve part.?? I want to be perfectly sure first before I purchase this part since it is quite expensive.
To be sure, I pulled out the error codes on the A/C switches and was expecting a B1417 code (duovalve left) but this code did not come up.
What came up are B1416 (coolant circulation pump) and a B1226 (in car temp sensor) Is this related to the aircon problem??
Thanks for any help..

That's got duovalve written all over it. I had the exact same thing happen on my C280. Your coolant pump code relates to the small pump on the right fenderwell that circulates coolant when you press the 'rest' button. It also assists the heater circuit at idle, othewise the duovalve opens to compensate for the low flow at idle, and when you take off, you get a blast of hot air until it can compensate. The sensor problem is one I'd have fixed at the same time.

__________________
'96 C280 (gone)
'97 C36
'05 C230k

Of course, where you live you'd never notice this.

__________________
'96 C280 (gone)
'97 C36
'05 C230k

Is the left side air actually heated, or merely outside temperature? The symptoms described are also typical of a 210 which is low on refrigerant and requires a recharge. Suggest checking this before replacing the duovalve as it is common and a much less expensive repair.

- JimY

No. Low on refrigerant will show a difference between center and outside vent temperature sometimes. A side to side difference split at the middle of the center vent is duovalve. Guaranteed.
Later or upper end models had the dual zone climate control, and on the earlier models, the system was the same, but the controls were not implemented. The duovalve can accomodate dual zone climate control, as the heater core has 2 separate circuits, each controlled by half the duovalve. On cars without dual zone controls, both solenoids of the duovalve are controlled by the same signal. When one solenoid fails, the difference in heating is split dead center in the middle vent. This failure can also be distinguished from a flap failure by the fact that the side vent is involved as well.

__________________
'96 C280 (gone)
'97 C36
'05 C230k

Wow!! thanks for those great inputs!! I'll ask one more advise please?

I went to a corner benz mechanic and he suggested plugging the hose from the duovalve going to the engine so that the hot coolant would not enter.

I do not need the heater anyway so plugging it with some rubber or whatever would be fine??

I tried disconnecting the duovalves but the aircon now blows weak air. So i just returned the connection since this was not right.

Hmmmm. Would plugging the hose be OK???

Not a good idea. The heater flow is required to modulate the evaporator temperature (i.e. prevent icing). Also. the duovalve is on the outlet to the heater, not the inlet. At least it is on all the diagrams I have seen. By blocking a hose, you disable the system's ability to do something it is trying to do, and it will overcompensate (if it can) somewhere else, or just not work quite right if it can't compensate.

__________________
'96 C280 (gone)
'97 C36
'05 C230k

Oh, by the way, the default for the duovalve solenoid is 'open', so by disconnecting it electrically, you allow full flow through the heater core on both circuits. Normally, when the interior temperature is just being maintained, the solenoid valves will both be closed, and will briefly pulse open often enough to maintain the required heater core temperature.

__________________
'96 C280 (gone)
'97 C36
'05 C230k

Good point. I didn't pick up that the temperature was different out the two sides of the center vent. That definately implicates the duovalve.

Nothing will get damaged in blocking the hose to/from the heater core - that's exactly the function of the duovalve! That said, you will lose some functionality by blocking the heater hose. When cooling demands are light (ie at night) the system is probably mixing in some heat to avoid overcooling the cabin of the car. You may find the car becomes uncomfortably cold, forcing you to switch off the aircon.

Also, the windshield defroster/defogger uses full heat to maximize removal of moisture from the glass. You'll lose much of the effectiveness if you block off the heater hose.

- JimY