HVAC question - PeachParts Mercedes-Benz Forum

mach0415 · #1 09-25-2010, 04:16 PM

I was wondering what the function of the duct going from under the knee trim on the pass and driver's side to an outlet to each of the front doors is. I never feel air going through them, and for that matter cannot imagine where in the door it would go. Also,I notice that the console register for the rear air never has air coming out of it. Any ideas?

toomany MBZ · #2 09-25-2010, 04:24 PM

They direct heat to inside the doors to help with defogging and front occupant comfort.

mach0415 · #3 09-25-2010, 06:47 PM

Ok. so if they do not function that mean a vacuum pod is defective? What about the console rear HVAC? and Do the front doors somehow have a passive register through the interior window wiper/belt mouldings?

toomany MBZ · #4 09-25-2010, 08:00 PM

It's the same flap, I believe, as the floor heat. My driver side failed, the wrist pin, or something, so I just propped it open (I used a spark plug, shhhh), now I have air blowing all the time.

Not sure I understand the second part of your post. But the front windshield is heated too (fourth pic) and the washer spray nozzles seem to have an electrical wire going to them so I'll bet they're heated as well.

mach0415 · #5 09-26-2010, 04:16 AM

When you say the front windshield is heated, what do you mean? I do see the hose and tube going through the firewall, but that is not the heater core is it? I thought defrost was heat - the far left button on auto temp control. How else could it be heated? The duct work going to the doors-is there an outlet at the bottom of the glass? or Does it just heat the air in the door?
My flap does the same thing. Looks like I'll be modifying mine too. Nice use of a spark plug!

toomany MBZ · #6 09-26-2010, 08:06 AM

The pics are from the epc, in the second one, item #110 is the "heater unit, windshield heating, below windshield".

The next time you have the heat on, feel around. It seems to have hot water circulating through it when the heater is turned on.

mach0415 · #7 09-26-2010, 09:05 AM

Okay, so #110 is a manifold, of sorts that the bottom of the windshield contacts, correct? SO, does the fan blow across this unit? or is it a stand-alone?

toomany MBZ · #8 09-26-2010, 11:00 AM

I'm not sure. The next time you have the heat on, see if you can feel any air being blown there outside.

whunter · #9 09-26-2010, 12:06 PM

Quote:

Originally Posted by mach0415

Okay, so #110 is a manifold, of sorts that the bottom of the windshield contacts, correct? SO, does the fan blow across this unit? or is it a stand-alone?

#110 is the heat exchanger = windshield heater unit.

This is a direct contact heater, not a forced air unit.

mach0415 · #10 09-26-2010, 02:34 PM

Cool! Thanks