I know there may be 100s of posts on this, but not sure where.

Since I am giving my mom my 300SEL and winter is here, I need to get the heat working properly for this cold natured lady.

For me, its fine, because heat does mostly blow out of the dash vents or defroster, but very little from the floor vents. I know this is a common issue, because my 85 380SE also had this issue, but it was worse, because I didnt get any air from the dash vents... defroster only.

I remember hearing something about some "pods" or something, but dont remember. Exactly what all steps and parts are needed to repair the no heat in the floor issue, on the W126 chassis?

Thanks in advance.

Well, upon further searching, I found a little more info, but really not step by step info on how and what is needed to repair this.

I even found a couple of old posts of mine from back in 2006 when I was having this issue on my old 380SE.

I did read where someone recommended closing the center dash vents if some air was coming out there and it is on my car, so we may try that for now and see if its sufficient for her. We may end up taking it to a MB shop somewhere and get this repaired if it dont cost a fortune.

Checking the vacuum lines as they connect to the vacuum control valve for supply & ability to hold vacuum.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Ding ding.

Check to make sure that vacuum switch is recieving vacuum, that the pod holds vacuum, and that the vacuum switch works before tearing out your dash.

Also, I think the procedure for troubleshooting the automatic climate control & replacing pods are on the FSM CD.

__________________
A.S.E Tech A1,A6,A7,A8 & MVAC 609 + EPA 608

Unless stated otherwise, any question I ask is about my greymarket 1985 380SEL.

Yep, FSM procedure 83-665 describes replacement of the vacuum pods. 83-600 tells you the locations of all 6 pods, and which switchover valves are connected to each pod.

Luckily, your center vents are working. That pod is the worst to replace, and is the only one that requires removal of the dash. Just last week I replaced my defroster pod and the two pods that control the main flap (for air recirculation). I had to take out my glove box, but that was it.

I'm about to do the leg flap pod, since it's been broken the whole time i've owned the car. That one is located directly behind the climate control unit on the center console. The FSM says you just need to pull the climate control unit (and wood above it) to get to it, but i'm preparing myself to remove the center console if my fat fingers can't do it.


**EDIT** But I just realized that you're talking about a Gen II, so it could be completely different. I know those have 7 switchover valves instead of 6, and I don't know the ways in which the layouts are different.

__________________
-Brian

1984 300SD, 375XXX miles, Light Ivory w/ Palomino TEX

You might want to check the electrical resistance thru each of the switchover valves. My car had 3 bad ones, and replacing them solved my vent open/close problems.

__________________
1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma

lol. Thanks for all of this information. However, I am pretty dumb when it comes to cars and I MAY be better off letting a local MB shop tackle this, as I dont want to screw anything up worse.

Next time I drive the car (Sunday), I am going to close the center vents and see how much air is allowed through the floor vents that way. Someone mentioned that if the center dash vents are working, then sometimes they can be closed to allow ample air to flow out the floor vents.... I am hoping.

Thanks again!

This is actually a pretty easy test, and I have found a way to do it without taking things apart.

The vacuum line feeding the entire CCU system is right there at the fake firewall by the fusebox - there is a 2-way check valve that it attaches to.

You can unplug that line and hook your mityvac to it. Then you can put the ignition to ON, and cycle through the various CCU functions watching for vacuum leaks as you do so.

Depending on what functions you have selected when the vacuum leak shows up, you can determine which pods are probably leaky.

Once you determine that you do indeed have a leak, you can narrow it down by getting to the solenoid bank that lives on the side of the center console, where the passenger's left shin would be. Hook up the mityvac to each output of the solenoid bank, and note which ones are leaky. The system diagram will then tell you which pods have to go.

In case you wonder what happens to these pods,

http://www.youtube.com/watch?v=sovTANrf3pM

__________________
-tp


1990 300SE "Corinne"- 145k daily driver - street modified differential - PARTING OUT OR SELLING SOON - PORTLAND OR. AREA - PM ME FOR DETAILS
1988 560SEL "Gunther"- 190K passes anything except a gas station
1997 S420 - 265k just bought it with a rebuilt trans. Lovely condition

Thanks for that info!

Well, I drove the car today for the first time since last Tuesday and I did that little test of closing the center dash vents with the sliders and presto, plenty of warm air blows from the floor outlets! I guess as long as they (center outlets) keep working this will be OK for now.

Thanks again!