Need your help guys,

My air conditioning is running well and blowing cold air. The only problem is that I generally cannot get any airflow from the center vents?

The system was running fine until about a week ago. Now it seems I cannot get ANY of the actuators to flap at any setting (DEF, ACC, EC, etc!). I AM getting 60 mm vaccuum at the manifold at the red/green line so engine vacccum appears to be okay? Strange is that none of the flaps seems to want to move under any setting.

I read some of the other posts and noted that I should check the actuators by applying vacccumm to each of them individually. I did this at the 6-way manifold on the right, with some of them opening. Once I got air to come out of the center vent but I could not repeat it (#4 vaccuum line at the manifold)....

Anyway, I am not skilled enough to remove the dash (as it seems this will be necessary to replace the center actuator)? Does anyone know exactly where it is located and can it be replaced without removal of the dash?

Otherwise, I am probably gonna need to take it to the dealer. Anyone have any idea about how much this is likely to cost ? 1000? 1500? (I guess I will need to have teh center actuator replaced and likely some of the other ones as well!?)


Thanks

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

check the actuator behind the glove box.... pull out box you will see if that one is working

__________________
1984300D 190,000 miles used everyday

Is the glove box easily removed??

If so, I will get on this right away. If this actuator is failing, is it easy to remove or is the dash going to need removal to get to it?

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

First, calm down. You don't have to remove the dash to work on any of the actuators. Even if the dash came off, it probably wouldn't help you do anything except get to the defrost vent actuator.

You have to study the vacuum diagram before testing the actuators at the junction block. The center vent actuator and one chamber of the defrost actuator are hooked up in parallel, or the vacuum hose equivalent of parallel. If you test one line at a time at the block, you'll think a couple of acutators are leaking. It's best to test the actuators themselves then test the lines and unions.

To remove the glove box, pry off the center pin of the seven rivet looking things around the opening edge of the glove box. Then pry off the cylinders the pins fit into. Pull off the glove box light and fit it through its hole. Pull out the glove box liner. The two actuators you'll see are the recirculation actuators. Both are dual chamber actuators. Test all four chambers.

Stick you hand in the glove box cavity, send it left then up. That's the defrost actuator and it's the third and last dual chamber actuator.

To get to the center vent actuator, open the ashtray, remove the receptacle, remove the two screws at the bottom of the ashtray frame (don't drop them into the abyss!), pull out the ashtray frame, reach in and pull out the radio and disconnect, remove the two screws at the lower corners of the radio cavity, pull out the climate control panel and disconnect (don't worry, the connectors are unique to each switch location and it doesn't matter which fiber optic line goes to which switch). In the upper right corner of the climate control panel cavity is the center vent actuator.

It might help to do all this with the right console panel off but you must be familiar with this if you tested the lines at the junction block.

Good luck.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Thanks guys for your help...I think I am close to solving this one. Mine looks the same as the one below from lastlane.

I removed the glove box and found this actuator to the left..I don't think you can see it without removal of the glovebox.




Taking it out wasn't too hard..is there any trick to installing it?
I may have to go dealer to get it ASAP but looks like fastlane has it (000 800 4375)

I manually turned the flap lever and I began to get cold air from the center flap!!! So this appears to be the problematic part. Looks like the other actuators are working. The other two seem to control a large rectangular flap piece (Directly to the front of the glovebox).

I took the above part apart and found some cracks and a 1cm hole in the rubber diaphragm...looks like this was causing me to lose vaccuum.

THe vaccuum lines appear to be intact, as I am obtaining suction on the red vaccuum line.

What is the second vaccuum line for?? To open the valve?
Thanks again for your help.

I will try to post some actual pictures, in case it may help someone down the line. I will post an update once the new part is in as well.

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

You can replace the broken rubber diaphram by using the parts from this site..... http://www.autoluxmbz.com/

__________________
Rick

'85 380 SL (sold)
'85 Carrera Flatnose
'71 280 SL Signal Red/Cognac

Those replacement diaphragms look nice, but I already ordered one from fastlane earlier today...$39 (vs $68 at the local dealer)

Are these actuators universal? That is, is each of the 6 unique or can they be used interchangebly?

If they are interchangeable I might keep this one on the shelf in case another goes bad and try the diaphragms next time

Here is the where the actuator found to have a broken diaphragm was located.

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

Hello,

I'm wondering if I have a problem with the two actuators in the picture below as well...the "flap" that they control closes when the system is on off ("0") by moving towards the front of the car.

Then, when the AC is on, it moves to about 1/2 way open but it seems like there is room for it to open all the way (towards the rear of the car).

Is this normal for it to be 1/2 way stuck? It seems the 2 actuators shown here work in conjunction to push the flap forward, and that the rear position is when no vacuum is applied?

BTW: I am correct in assuming this is the recirc flap?

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

Difficult to keep up with your questions. Let's try these answers:

- the two recirc actuators and the defrost actuators have two vacuum lines each and as you might imagine have three positions - closed, ajar and open. You'll have to look at an ACC function matrix to see which positions the actuators should assume given under various conditions.

- the recirc actuators should close the recirc flap when the engine is running and the ACC system is in the off position. This MIGHT not be the same as just turning off the engine. I don't expect the system holds vacuum for very long when the engine is turned off so I wouldn't be surprised if the recirc flaps opens after some time of having the engine off.

- AFAIK the actuators are not interchangeable. I doubt you can replace a single chamber actuator with a dual chamber actuator unless you fed both chambers off the same line, and a single chamber actuator can't perform the partial function of a dual chamber actuator. If actuators come with rods then they're definitely one for each purpose. AFAI remember, the center vent actuator has a different rod attachment methods from the rest; that is, not that split white plastic cap over the hooked end of a rod. In fact I think it's a rivet.

- My guess is that the leaky chamber you identified in the defrost vent actuator is the one that shares a vacuum signal with the center vent actuator. Plugging the leak allowed the center vent actuator to function.

- That is the recirc flap and actuators in the last photo.

- I have no idea what I'm looking at in that photo with the yellow plastic wrap

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Sixto,

Thanks for all your help and I appreciate you keeping up with my questions. If I understand you correctly, the above "flap" does indeed have three positions as you stated: closed, ajar and open. So it seems the system is performing as it should.

I don't think those recirc/flap actuators are malfunctioning and I am going to leave them alone for now...they seem easy enough to get to if something else is suspect.

As an aside, for the center vent, as you mentioned earlier, there DOES appear to be another "center-vent" actuator somewhere else, as I can get loss of air from the center vent when disconnecting vacuum hose 5/6 at the vacuum hose manifold WHILE manually opening the defrost vent lever--that OTHER actuator (wherever it is) is working fine as well.

Botttom Line is that the only one malfunctioning appears to be defrost vent actuator which is on order. (The first picture-the one without the actuator in the shot, is where the defrost actuator WAS-before I removed it).

YOu are right in that the pushrods appear to differ on each of the actuators...luckily fastlane has the one I need.

So it seems I have identified:
(2) recirc actuators
(1) defrost actuator (one missing in the picture)

Again Thanks for your Help and I will keep you posted...I am thus far amazed at how simple this now seems compared to what everyone was describing in the other posts I read.

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

Rest assured there is a dedicated center vent actuator. I settled on a new diaphragm for that one.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

I have the exact same problem! I'd be willing to bet that it is the same actuator too! Just one question of clarification. Which vent is it that you replaced, the one that shares the vacuum with the center vents. Was it the one behind the A/C panel or the one behind the glove box and to the left?

I think I will give the repair kit a try....I wonder if the $10 opener is necessary.....

__________________
'86 420SE Euro
904 Midnight Blue, Gray Velour
Dad bought it new, now I own it.

"A Mercedes-Benz is like a fine wine, it only gets better with age."

The tool might be nice because it's all too easy to break a tab on these brittle actuators.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

in my situation it was NOT the one(s) that are seen when the AC wooden console is removed, this was just to the left of the removed glovebox.

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)

Well,

now everything is assembled and appears to be working smoothly except for one problem

THe climate control temerature dial doesn't seem to allow for proper temperature control...that is, the car will cool to 22C (if set there), but when it slows down, it switches to heat momentarily sometimes and then back to cool etc?

Luckily I have two identical cars, so the first thing I did is swap the two other climate control relays - temp & blower control...

Still didn't solve the problem? My next guess is that the interior temp sensor may be bad.

BTW: The monovalve has ALREADY been replaced last year. And the pushbutton relay was just changed last month (part of the center vent problem as above).

__________________
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)