S210 Residual heat

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There may be nothing wrong with the pump at all, it might, for example run for 5 minutes and then stop because the battery is not up to scratch or because the temperature of the coolant is not high enough… or the system thinks the coolant temperature is not high enough.

If the pump runs for a very short time or if it doesn’t run at all it would be wise to unplug the pump and put an independent power supply to the pump motor … a battery charger perhaps… to see if it will run without any influence from sensors within the system.

You would need to stand there and monitor the system just to see how long it will run for.

Dec
 
I've now had a look for the pump and found it! It's in a very accessible place just underneath the air filter. It has only two pipes going to it, one of which leads directly to the duo valve.

I only had chance to test it when it is stone cold, but the interior blower blew all the same. This suggests that a low water temperature would not prevent the residual heat system from working.

Anyway, the water pump was silent. I gave it a sharp tap with my finger and then it started. I spent a few minutes fiddling and it kept cutting in and out and going fast and slow. So, maybe it's got a bad electrical connection. I'll check the electrical connector sometime (when it's not cold and dark!).

Since the pump is connected directly to the duo valve, this must mean that water is flowing through it at all times. But, when the engine is running, I wonder if the water is pumped solely by the main water pump, or if the electric pump should also work?
 
I tested my W202 system when the engine was fully hot and got about 30 minutes of cabin heating, the temperature of the air at the vents after 30 minutes was about 33c, (92F) no condensation inside at all so I presume the outside air intake flap was closed automatically… otherwise humid air would have entered the cabin and misted up the windows as air con was off with engine off.
Must try running the system when engine is cold to see how long it will pump for.

A think a W210 should work in much the same way, can’t see the point in the electric pump running while the engine driven water pump is circulating the coolant.
I think the electric pump is for residual heating only, you will need to test it when it’s hot, and perhaps it was cutting in and out because the coolant temperature was cold?

Dec
 
Your right, low water temperature wont stop the blower/pump from working, tried mine this morning on a cold engine and it ran for 30 minutes.

Dec
 

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