I cant wait to sit in your A/C .... shhhh don't tell my car though she'd throw a fit! Good job on getting that all figured out!
A/C Center Vents not working - FIXED! FINALLY! Diagnose A/C Vacuum Problems DIY
Okay, so most of you know that I have had issue with my Air Conditioning Center Vents not working and all of the cold air was going up through the defroster vents. This does no good with a fully charged system, let alone one on the edge as mine is/was.
So the vent flap system in our Mercedes are moved by means of vacuum "Pods" that when vacuum is applied, a diaphram is moved that is connected to a rod which is in turn connected to the flap in question. In this case the "40" Pod moving the Center flap.
So I went to Harbor Freight and bought their $20.00 combination vacuum tester and brake bleeder kit. A very well made device considering it's origin.
So the first test is to see what we are drawing at the vacuum source off the banjo bolt on the rear of the intake manifold. There are on my two 560's, two vacuum sources there. The bottom on goes to the kick-down on the transmission and the upper one comes out straight back and then into a rubber 90 Deg Elbow and then via vacuum tubing goes over to the drivers side secondary firewall. There (on my cars) it is split into a 4-way. 3 in and 1 out. The three sources on my car (The sedan is a little different because there is no vac line to the seat locks) One of them goes straight from the Tee to the instrument cluster for the ECON gauge. The other two go to Check Valves. There are two 2-Ways. 2 In and 1 out. The "Out" side is in the engine compartment and each one goes to one of the two remaining ports (You may only have a 3-way depending on model of car. My sedan has a 3 way, not a 4 cross).
So that give 4 vac ports, 2 of 2, So the vacuum storage bottle and the A/C vac source lines go on one of the two Check Valves. See attached diagram. CV #36 is the one at the firewall, and that does not show the 4 or 3-way there.
The other CV if you have one (Like on a Gen II coupe) is for the Headlight Adjusters and for the seat back vacuum locks, both of which my car has. Neither the SBL's or the HLA's need a reservoir of vacuum, only the A/C pods. One could argue that the HLA's should also go on that circuit so that engine power does not fluctuate the Headlight Height, and I will test that and report back results. I do know that my Headlight height needs adjusting since the AMG suspension went in.
Back to the vacuum problem. So I checked vacuum at the source, good at 17Hg and holding steady. Then I plugged in the CV and rigged up a tee and put the meter to the A/C side. I only got 5Hg at most so there was a definite leak somewhere in the system. So I was faced with taking out the DVD Control Head and the A/C Wood panel. People wonder why it takes me no time do do stuff... Practice my friends.... Practice... So out came the radio for the second time this week and I HATE doing it because it is held in with 4 TINY LITTLE screws and I usually lose a couple in the process. But not the last two times.. Again.. PRACTICE...
So I got the panel off and I took off the main feeder line, the RED/BLUE one that goes from the CV #36 to the #48 "7 Point Distributor" a rubber/plastic assembly that feeds the 6 solenoids. I took it off and put my thumb over that and Viola! The gauge read 14Hg! Went up right away. So the CV/Tank/Feeder line all good to the 7-Point. So! Leak in the system.. Which one???
So What I did was then take out the pass carpeting and then take off the side panel to the center console revealing most of the "Gang of Six" as I have taken to calling it.
What this "Gang of six" solenoids does is open and close based on the pushbutton control mode (PBC) So in Max it opens and closes the "Pods" to move the flaps as necessary.
There are six "Pods"
38 - DEF nozzle flaps - This is a "Double Action" meaning it is spring loaded but needs vac on both side to open and close
39 - Leg Flaps - Single action
40 - Center Nozzle - Single Action
41 - Air Scoop - Single Action
42/43 - Fresh/Recirculate - This is a Dual Connection/Double action type setup, meaning that there are two pods and the pushrods are connected because it needs that much torque to open and close the flap due to the amount of resistance of air entering at 140+ MPH.
So what I did was go one by one and remove the little elbows on the left of the GO6 until I found the leaky one. It turned out to be the #16 valve. Well not the valve because when I covered that port with a cap (You can get a set of vacuum caps at any auto parts store for $3.00) the gauge went up to 14Hg and the center vents came open instantly!
So I looked at the attached chart and it was the last page. The 42 and 43 pods are ganged together so that it is a 2 length stroke. When valve #17 opens, it goes 80% of the way so that 80 of the air going through the exchanger is cabin (ambient) air and 20% is fresh (outside) air. When you select the "OFF" position, the #16 valve opens and draws the 42/43 combo to pull further closed and completely close off the cabin from outside air. In a properly operating system with the vacuum storage bottle attached and holding containment, the 42/43 pods will remain closed even with ignition off.
This is one of those "Fortunately/Un-Fortunately" situations for me. Wile of late I have been fanatical of fixing everything I can back to factory specs, I realize where these two valves are (UNDER the dashboard top cover) and are a complete bitch to get to. I am sure some day I will crack that open, but I had no desire to do it today so I did the only thing I could and that was to leave that line disconnected and leave the vacuum cap in place.
Daddy's Girl is due here in 3 weeks and her only request was working A/C in all my cars, and that's not too much for a girl to ask. So it is....
So the bad part is that the car will never be completely sealed until I get in there and fix it.. No biggie in the grand scheme of things. Even if I lived in the frigid north, I always like a little cold air in and in all A/C modes that circuit is never activated. Only in the "OFF" position and my ACC is NEVER off. In the summer it's always in AC mode and in the Winter Heating. So that circuit is never needed in real world practice. And J'aime will be cool and happy.
In the last pic, the fender vac bottle, the CV labeled #17 is #36 in the top two diagrams. #17 is the item number in EPC where that drawing came from.
Now a couple of other tips. Let's say it's one of the other pods you can't live without. Well then you will maybe have to crack the dash open. The 40 and I think 41 pods are easy to get to and repair.
So I hooked everything up like it is supposed to be and took it out for a ride. The vents never cycled once and the system worked perfectly in all modes.
Now, for the remaining issue and that is air temp coming out of the vents. There ARE bubbles in the sight glass so there is probably a pin hole leak in the lines somewhere. I called around and it took me all of 10 minutes on the phone to find a local shop that was willing and able to charge my A/C with R-12 for $75.00. It is a local shop that does work on MB's and I quizzed the guy and he knew chassis and body codes so that was encouraging. So a top off is all it needs as it had a full charge last October when I put it on the road. So it probably has a tiny leak if at all. But a top off is in order. He said it would take half the day. In by 10AM out by 2PM. Could not ask for better.
I do want to address this final point. Yesterday and this morning, had I not found this mechanic (And if he fall through) was going to go the R-290 (Propane Route). I know there has been heated debate over this of late as I have participated in it myself.
I will say this: If and when the time comes that a rebuild/overhaul is needed, I will do as my good friend Mike Ramay did (and will be using the Viton O-Rings he sent me (Thanks Bro!!) to rebuild) and convert to R-290.
Anyone that says "PROPANE WILL KILL YOU IF IT'S ALLOWED ANYWHERE IN THE CABIN" has never owned a Motor Home. I have owned two: A 33 Horizon and a 40' Providence Diesel pusher with a Cat D7. I had a 75 Gallon Propane tank that ran all major systems. Water heater, cabin heater, refrigerator and stove. In some cases even the A/C units themselves are propane powered and some generators. Anyone that's been in the camping world (Or In Camping World) knows this... All propane and all systems are fueled by propane and are directly IN THE CABIN WITH YOU.....
So stop with all the doom saying... We get it... As someone just posted, it appears if the nay-sayers have never done it and I have spoken at length with the people doing it successfully. I, like Mike Ramay and Abdullah (You Rock Bro!) live in the hot ass desert. I live in the Hot ass desert, I can only Imagine what kind of hell Abdullah you live in man... You use what-the-hell-ever cools your car.
There, enough soapbox...
So there you have it.... I have enclosed pics charts and diagrams to guide you guys (and Girl!) and as always I am here to answer any more specific questions.
Good Luck! I hope this is of help to someone someday!
So the vent flap system in our Mercedes are moved by means of vacuum "Pods" that when vacuum is applied, a diaphram is moved that is connected to a rod which is in turn connected to the flap in question. In this case the "40" Pod moving the Center flap.
So I went to Harbor Freight and bought their $20.00 combination vacuum tester and brake bleeder kit. A very well made device considering it's origin.
So the first test is to see what we are drawing at the vacuum source off the banjo bolt on the rear of the intake manifold. There are on my two 560's, two vacuum sources there. The bottom on goes to the kick-down on the transmission and the upper one comes out straight back and then into a rubber 90 Deg Elbow and then via vacuum tubing goes over to the drivers side secondary firewall. There (on my cars) it is split into a 4-way. 3 in and 1 out. The three sources on my car (The sedan is a little different because there is no vac line to the seat locks) One of them goes straight from the Tee to the instrument cluster for the ECON gauge. The other two go to Check Valves. There are two 2-Ways. 2 In and 1 out. The "Out" side is in the engine compartment and each one goes to one of the two remaining ports (You may only have a 3-way depending on model of car. My sedan has a 3 way, not a 4 cross).
So that give 4 vac ports, 2 of 2, So the vacuum storage bottle and the A/C vac source lines go on one of the two Check Valves. See attached diagram. CV #36 is the one at the firewall, and that does not show the 4 or 3-way there.
The other CV if you have one (Like on a Gen II coupe) is for the Headlight Adjusters and for the seat back vacuum locks, both of which my car has. Neither the SBL's or the HLA's need a reservoir of vacuum, only the A/C pods. One could argue that the HLA's should also go on that circuit so that engine power does not fluctuate the Headlight Height, and I will test that and report back results. I do know that my Headlight height needs adjusting since the AMG suspension went in.
Back to the vacuum problem. So I checked vacuum at the source, good at 17Hg and holding steady. Then I plugged in the CV and rigged up a tee and put the meter to the A/C side. I only got 5Hg at most so there was a definite leak somewhere in the system. So I was faced with taking out the DVD Control Head and the A/C Wood panel. People wonder why it takes me no time do do stuff... Practice my friends.... Practice... So out came the radio for the second time this week and I HATE doing it because it is held in with 4 TINY LITTLE screws and I usually lose a couple in the process. But not the last two times.. Again.. PRACTICE...
So I got the panel off and I took off the main feeder line, the RED/BLUE one that goes from the CV #36 to the #48 "7 Point Distributor" a rubber/plastic assembly that feeds the 6 solenoids. I took it off and put my thumb over that and Viola! The gauge read 14Hg! Went up right away. So the CV/Tank/Feeder line all good to the 7-Point. So! Leak in the system.. Which one???
So What I did was then take out the pass carpeting and then take off the side panel to the center console revealing most of the "Gang of Six" as I have taken to calling it.
What this "Gang of six" solenoids does is open and close based on the pushbutton control mode (PBC) So in Max it opens and closes the "Pods" to move the flaps as necessary.
There are six "Pods"
38 - DEF nozzle flaps - This is a "Double Action" meaning it is spring loaded but needs vac on both side to open and close
39 - Leg Flaps - Single action
40 - Center Nozzle - Single Action
41 - Air Scoop - Single Action
42/43 - Fresh/Recirculate - This is a Dual Connection/Double action type setup, meaning that there are two pods and the pushrods are connected because it needs that much torque to open and close the flap due to the amount of resistance of air entering at 140+ MPH.
So what I did was go one by one and remove the little elbows on the left of the GO6 until I found the leaky one. It turned out to be the #16 valve. Well not the valve because when I covered that port with a cap (You can get a set of vacuum caps at any auto parts store for $3.00) the gauge went up to 14Hg and the center vents came open instantly!
So I looked at the attached chart and it was the last page. The 42 and 43 pods are ganged together so that it is a 2 length stroke. When valve #17 opens, it goes 80% of the way so that 80 of the air going through the exchanger is cabin (ambient) air and 20% is fresh (outside) air. When you select the "OFF" position, the #16 valve opens and draws the 42/43 combo to pull further closed and completely close off the cabin from outside air. In a properly operating system with the vacuum storage bottle attached and holding containment, the 42/43 pods will remain closed even with ignition off.
This is one of those "Fortunately/Un-Fortunately" situations for me. Wile of late I have been fanatical of fixing everything I can back to factory specs, I realize where these two valves are (UNDER the dashboard top cover) and are a complete bitch to get to. I am sure some day I will crack that open, but I had no desire to do it today so I did the only thing I could and that was to leave that line disconnected and leave the vacuum cap in place.
Daddy's Girl is due here in 3 weeks and her only request was working A/C in all my cars, and that's not too much for a girl to ask. So it is....
So the bad part is that the car will never be completely sealed until I get in there and fix it.. No biggie in the grand scheme of things. Even if I lived in the frigid north, I always like a little cold air in and in all A/C modes that circuit is never activated. Only in the "OFF" position and my ACC is NEVER off. In the summer it's always in AC mode and in the Winter Heating. So that circuit is never needed in real world practice. And J'aime will be cool and happy.
In the last pic, the fender vac bottle, the CV labeled #17 is #36 in the top two diagrams. #17 is the item number in EPC where that drawing came from.
Now a couple of other tips. Let's say it's one of the other pods you can't live without. Well then you will maybe have to crack the dash open. The 40 and I think 41 pods are easy to get to and repair.
So I hooked everything up like it is supposed to be and took it out for a ride. The vents never cycled once and the system worked perfectly in all modes.
Now, for the remaining issue and that is air temp coming out of the vents. There ARE bubbles in the sight glass so there is probably a pin hole leak in the lines somewhere. I called around and it took me all of 10 minutes on the phone to find a local shop that was willing and able to charge my A/C with R-12 for $75.00. It is a local shop that does work on MB's and I quizzed the guy and he knew chassis and body codes so that was encouraging. So a top off is all it needs as it had a full charge last October when I put it on the road. So it probably has a tiny leak if at all. But a top off is in order. He said it would take half the day. In by 10AM out by 2PM. Could not ask for better.
I do want to address this final point. Yesterday and this morning, had I not found this mechanic (And if he fall through) was going to go the R-290 (Propane Route). I know there has been heated debate over this of late as I have participated in it myself.
I will say this: If and when the time comes that a rebuild/overhaul is needed, I will do as my good friend Mike Ramay did (and will be using the Viton O-Rings he sent me (Thanks Bro!!) to rebuild) and convert to R-290.
Anyone that says "PROPANE WILL KILL YOU IF IT'S ALLOWED ANYWHERE IN THE CABIN" has never owned a Motor Home. I have owned two: A 33 Horizon and a 40' Providence Diesel pusher with a Cat D7. I had a 75 Gallon Propane tank that ran all major systems. Water heater, cabin heater, refrigerator and stove. In some cases even the A/C units themselves are propane powered and some generators. Anyone that's been in the camping world (Or In Camping World) knows this... All propane and all systems are fueled by propane and are directly IN THE CABIN WITH YOU.....
So stop with all the doom saying... We get it... As someone just posted, it appears if the nay-sayers have never done it and I have spoken at length with the people doing it successfully. I, like Mike Ramay and Abdullah (You Rock Bro!) live in the hot ass desert. I live in the Hot ass desert, I can only Imagine what kind of hell Abdullah you live in man... You use what-the-hell-ever cools your car.
There, enough soapbox...
So there you have it.... I have enclosed pics charts and diagrams to guide you guys (and Girl!) and as always I am here to answer any more specific questions.
Good Luck! I hope this is of help to someone someday!
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Propane fill rig
The yellow hose fittings have rubber inserts in them, the black tip in the bottom of the picture, as does the separate adapter fitting. When I put this on the car, I've found that finger tight is enough that it doesn't leak. Screw valve assembly on the propane bottle, screw the yellow hose onto the torch valve assembly, screw the adapter onto the R12 fitting on the car, screw the yellow hose onto the adapter, open the valve.
Your temperature out of the vent is about 20F too high. Driving at pretty much any speed (15mph +), I've been getting 40F air out of the SEC vents, on propane, with OAT at 100F or a few degrees up. I saw 110F while going through Phoenix and Tucson, AZ on the highway and I was still getting 50-55F out of the vents. The cabin was such a good temperature that I was surprised to look at the OAT gauge and see 108F right there. I reached up to touch the windshield to verify it really was that hot! It was.
The bottom picture is the reason I need to refill my system!
Below is a photo of my new and improved propane fill rig. I would recommend spending the bucks to get this instead of that $12 hose. I purchased two of these Johnsen's Freeze 12 Quick Charge Kits (~$14 ea, part no. 8523 at CarQuest) because I wanted two of the adapters. I was in Sierra Vista, AZ (14m N of Mexico) and they couldn't find anything like the adapter in the hardware stores. I took a BenzOmatic torch valve assembly and unscrewed the torch tip. The end of the tube looked like it was blanked off so I sawed that off and opened the hole in the end with a 1/4" drill. Nobody could find an adapter to change the BenzOmatic tube thread to the R12 adapter thread, so in the motel room, I put some JB Weld Kwik on the tube and adapter threads and used a big wrench to screw them together. The JB Weld made sure that there is no gas leak and big wrench got me several turns so that there is sufficient mechanical strength. Not elegant, but ....
The yellow hose fittings have rubber inserts in them, the black tip in the bottom of the picture, as does the separate adapter fitting. When I put this on the car, I've found that finger tight is enough that it doesn't leak. Screw valve assembly on the propane bottle, screw the yellow hose onto the torch valve assembly, screw the adapter onto the R12 fitting on the car, screw the yellow hose onto the adapter, open the valve.
Your temperature out of the vent is about 20F too high. Driving at pretty much any speed (15mph +), I've been getting 40F air out of the SEC vents, on propane, with OAT at 100F or a few degrees up. I saw 110F while going through Phoenix and Tucson, AZ on the highway and I was still getting 50-55F out of the vents. The cabin was such a good temperature that I was surprised to look at the OAT gauge and see 108F right there. I reached up to touch the windshield to verify it really was that hot! It was.
The bottom picture is the reason I need to refill my system!
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