Are there foot heating vents in my 83 300D? - Page 2 - PeachParts Mercedes-Benz Forum

Maki · #16 11-21-2004, 12:01 PM

I just replaced the defroster pod yesterday in my '82 300td. After taking the old one apart (it's easier to remove if you dismantle it before trying to undo the bayonet mount, IME) I'd say that rebuilding it would be a pretty involved job. One of the diaphragms is installed (with a coil spring) between two hard plastic caps that are connected with a brass swivel that is pressed into each cap. You'd probably have to destroy the swivel to remove it, then find something of equal dimension to replace it. Then drill out the pieces of the old one, etc. etc. It's not just a matter of popping in a diaphragm or two.

The other W123 pods are a different story -- in fact, I think the one for the center vents is easier to rebuild in situ than it is to remove!

By the way, I found the bayonet mount on the replacement pod I received had been installed backwards. I had to remove that piece and reinstall it correctly so the actuating arm was positioned the way it was supposed to be.

Russ M

Maki · #17 11-21-2004, 12:11 PM

[QUOTE=eskimo]OK, just to be clear, we are talking about a vacuum actuator that's oriented horizontally, and is located directly behind the ductwork leading to the foot vents, yes? I'm thinking about the vents down low on the left and right side of the center column of the dash, with one vacuum actuator that uses a linkage to operate the flaps together (one on each side). If I'm using the wrong nomenclature here, then please, someone correct me.

Eskimo --

My experience is that it's the defroster pod that fails (I've replaced two on two cars), perhaps because it's generally under vacuum when the car is operating. It's the James Brown of the ACC system -- the hardest-working actuator in the climate control business.

When it fails, the vent system defaults to defrost mode, so your footwell heat goes away. It's the big vertical pod in back of the ignition switch with two hoses connected to it.

Russ M

Eskimo · #18 11-22-2004, 10:14 AM

Quote:

Originally Posted by MonsieurBon

I took out the underdash panel and looked at the vacuum pod. It's fairly accessible. Problem is, I tried actuating the lever it attaches to and it didn't blow any air out of that hole.

So given what you're saying, I should get the car warmed up before I try that. I was trying it with the car cold in the garage and turning the heat control to max and the blower at max.

So it sounds like it's intelligent enough to not blo cold air on your feet, eh?

OK, I did a reality check this morning with the car cold (OK, it's not that cold here, but the engine hadn't warmed up yet).

Rolled the temperature control up to a high temp. setting, had center vents close and foot vents open. Rolled it back down, had foot vents close and center vents open. It didn't seem to care that the engine was cold.

By the way, I've experienced the blown defrost actuator thing, too. As others here have pointed out, it dumps loads of air up through the defrost openings, and not all that much anywhere else.

MonsieurBon · #19 11-22-2004, 09:57 PM

Quote:

Originally Posted by mb123mercedes

Try this:

http://www.autoluxmbz.com/

Louis.

Awesome! I will have to get some stuff from these guys. Thanks!

MonsieurBon · #20 11-22-2004, 10:00 PM

Quote:

Originally Posted by eskimo

OK, just to be clear, we are talking about a vacuum actuator that's oriented horizontally, and is located directly behind the ductwork leading to the foot vents, yes? I'm thinking about the vents down low on the left and right side of the center column of the dash, with one vacuum actuator that uses a linkage to operate the flaps together (one on each side). If I'm using the wrong nomenclature here, then please, someone correct me.

I think the "smarts" of the ACC system decide when it should "try" to open those flaps, but if you're mechanically reaching in and moving things, I don't think it can matter what the ACC "thinks" about the temperature of the car. If you're physically moving the mechanism to open those flaps, then I think air should come out of them. You should be able to directly see if they're open or shut - the flaps are right there where the air comes out.

As an aside, I'll repeat that I think that the ACC is also supposed to close off the center dashboard vents when delivering heat (deliver more to your feet, and help give your eyeballs a break).

Ahh.. I was looking at a vertically oriented vacuum actuator mounted to the left side of the footwell duct on the driver's side. Is that actually the one that opens the center vents on the dashboard? When I moved the linkage it attached to, I could hear a blowing sound from somewhere higher up.

So I probably need to look further back, closer to the accelerator?

Thanks!

Eskimo · #21 11-22-2004, 10:33 PM

Quote:

Originally Posted by MonsieurBon

Ahh.. I was looking at a vertically oriented vacuum actuator mounted to the left side of the footwell duct on the driver's side. Is that actually the one that opens the center vents on the dashboard? When I moved the linkage it attached to, I could hear a blowing sound from somewhere higher up.

So I probably need to look further back, closer to the accelerator?

Thanks!

The vertically oriented vacuum actuator on the left side is the one for the defroster.

Yes, you will be looking to the right of the accelerator pedal, behind the lower middle section of the dash (again, I don't know the right word for it). For me, I found it convenient to remove both driver and passenger side underdash panels to gain access. A flashlight and a mirror helped, too.

Maki · #22 11-23-2004, 02:33 AM

Just curious, MonseurBon -- have you got a Mytivac? It's a pretty handy tool for sleuthing out vacuum leaks. If you have a Harbor Freight store in you area you could probably pick up a cheap knockoff version.

Russ

bbeardb · #23 12-22-2005, 03:08 PM

Quote:

Originally Posted by eskimo

OK, just to be clear, we are talking about a vacuum actuator that's oriented horizontally, and is located directly behind the ductwork leading to the foot vents, yes? I'm thinking about the vents down low on the left and right side of the center column of the dash, with one vacuum actuator that uses a linkage to operate the flaps together (one on each side). If I'm using the wrong nomenclature here, then please, someone correct me.

So what if only the passenger side opens and the drivers stays shut? That is what happens with mine. Not a big deal right now though because I'm not driving it in the winter, but still...

Eskimo · #24 12-22-2005, 04:10 PM

Quote:

Originally Posted by bbeardb

So what if only the passenger side opens and the drivers stays shut? That is what happens with mine. Not a big deal right now though because I'm not driving it in the winter, but still...

There's some sort of mechanical linkage back there to allow one vacuum actuator to operate both flaps. I don't remember the details, as I was just in there long enough to replace the actuator.

A suitable work light and inspection mirror might let you eyeball the situation back there to determine if something is broken or disconnected.