a/c blows nothing but hot air, 1980 300sd - Page 3 - PeachParts Mercedes-Benz Forum

97E300D · #31 07-17-2006, 01:12 PM

I've overhauled these servo before and I would not recomend messing with it right now, with the 90-100 degree heat and all. I would simply clamp off the heater hose. You will most likely have cool air coming in.. since the vacume contol servo is already in position to allow the Compresor switch to close and turn on the compressor. If in fact you don't seem to get any cold air coming in then ensure the compressor line is getting cold, this will tell you the the eveporator is cold. You then just need to enusre air is blowing through it...If not... then you can access the vacume lines fromthe 8-10 lines connected to the servo. You may need to cut a hose, block off one end with a golf tee, and apply vacume by sucking or using a mity vac until the right one is discovered. If you find it pul enough vacume on the line then clamp it with pliers and stick a golf tee in it to hold vacume.

Other wise getting under the dash my be the only other option, yet I think you should be able to get cold air by just clamping the "Heater Hose".

When you push the buttons on the dash do you hear the flaps opening and closing, and does the air flow switch from Defrost to vents and to floor?

topanga · #32 07-17-2006, 01:39 PM

the best thing about this car really is the community of people who make it possible to fully enjoy it. I'm really grateful for all your suggestions, and I thank you for putting up with my gibberish.

We're GETTIN' there! I have been able to locate my compressor and the hose coming out of it (in case anyone is searching archives, on my 116 this hose runs right along the top of the guts straight into an opening just ahead of the steering wheel) is nice and cool. So I'm partway there... will shop for my homemade monovalve this evening.

topanga · #33 07-17-2006, 01:47 PM

Quote:

Originally Posted by 97E300D

When you push the buttons on the dash do you hear the flaps opening and closing, and does the air flow switch from Defrost to vents and to floor?

the vent pattern changes ONLY when Defrost is engaged, otherwise it's always floor vents and the -- don't know what to call it -- handle-like vent attached to the frame at knee level next to the door. The vents at the sides of the dash register no air flow, nor do the ones atop the instrument cluster. With Defrost engaged, the vent below the glass roars; without defrost, this vent trickles air.

There does seem to be some cool air flowing from the knee-level vents, I THINK. It might just be that any air moving inside a 120 degree passenger cabin feels cool. I could be wrong; it could just be hot air. I am hopeful there's some cool there that will really announce itself once the hot is stoppered.

When I engage the buttons, I do hear the chunking sound of some vents, but only between defrost on and defrost off. Not with temp adjusted, not lo to hi, not in any other case. I experience quite a power hit when I engage a/c and cool tubes, so I am confident that's all operational.

riethoven · #34 07-17-2006, 01:51 PM

Quote:

Originally Posted by topanga

I am driving the car my husband left me when he died slowly of lung cancer at age 48, bankrupting us as a catastrophic illness will, and trying to keep up with the bills it incurs intelligently, rather than have mechanics rip me off, because this car is one of the few things that makes me feel his presence and makes me feel like I am still honoring something of his memory now that he is dust.

So, you know, excuse me for giving it all a shot. Wanna be in my shoes?

My condolensces on your husband. 48 is way too young.

I think the guy who recommended the shops in southern CA thought you were in Topanga Canyon because of your user name. Go to your signature and list your location so others will know.

Regarding your car and other old MBs, others who have written in are correct. These are great cars and are fairly cheap to maintain if you do your own work. Repairs can be another story, but still not too bad if you do your own work. The problem comes in when you start taking them to a garage with unqualified people who use your car as on the job training while they are billing you. That is the main reason that I do my own work, and most of the time I do the repair better and more quickly if you consider the time spent waiting at the repair shop.

I must say that I was impressed that you were able to get the door panel off to check out the window regulator. I know that this is sexist but I see so few females doing their own work. The same thing happened to mine and I fixed it myself with a couple of dollars worth of fasteners, and it is working great.

Look and see if the service manual is available online. (the W123 is) This is a tremendous resource as is the shop forum.
I wish you the best of luck.

rs899 · #35 07-17-2006, 01:56 PM

topanga-

For the record, the service manual is at www.w116.org ( as well as a lot of other neat stuff about history etc). Its a group out of Australia- mostly gassers but good folk there. They won't be able to help much on evil servo issues as they only had the simple manual controls (lucky them).

Rick

topanga · #36 07-17-2006, 02:48 PM

that 116 link is great. I visit 300sd.com quite a bit.

The door panel removal was as easy as pie, just a bunch of screws and then lift, and I saw the problem of the gear mis-fit right away. I really was bummed that I couldn't get the regulator out. Even if I had removed it, I don't suppose I could have realigned the gears. If I could find a cool garage, I'd give it some more time. I'm still going to replace the switch as long as I have the dash open. I had to replace the driver one last year and have had the extra all this time. Maybe it will unstick the rear passenger window, who knows. It's a bummer because some of the repair and maintenance have been a snap (antenna mast motor, oil changes, switches), and some are too advanced for me.

48 was, yes, WAY, WAY too young. I have to think there was a reason, and it has made me savor life a lot more knowing that it can be brief. If there's one thing I can share with people, it's the importance of early diagnosis and APPROPRIATE diagnoses with cancer. My one piece of key info for anyone facing a cancer diagnosis is: ASK FOR A PET TEST. PET test. PET test. PET test. Accurate staging is EVERYthing. I sincerely hope that this is useless information for everyone and none of you ever have to use it.

I forgot about adding my location to the profile, sorry. We called the car "Topanga" because that's where we used to live.

topanga · #37 07-17-2006, 03:02 PM

am having trouble figuring out which hose I'm mono-valving. Such a tangle coming into and out of the servo and none of it quite resembles the pic.

There's a hose that goes to the servo and enters the dash about four ins. from the known cool hose. Is that the one I'm stoppering? Can I stopper it THERE, between dash and servo? That seems the most accessible place. I feel like I ought to post a webcam shot of it to make sure. Yes?

97E300D · #38 07-17-2006, 03:14 PM

The one runs into the fire wall (Dash) should be fine. Clamp it closed before you cut it to install the valve. You can get away with just clamping it for now. In the winter you can install a cable operated contol valve that can be controlled from inside the car. That is what I did on my 77.

Come on now Clamp that hose closed and tell us if the Air is cold..........

rs899 · #39 07-17-2006, 03:16 PM

I would have to look at it, but I think the one that runs through the aux water pump ( the little electric motor just outside of the servo) would be the one you want. I , personally, would shut it off BEFORE the servo, just incase the servo decided to crack and leak. I would disconnect the plug on that motor , too, for now.

Rick

you go girl!

rs899 · #40 07-17-2006, 03:22 PM

This guy

http://www.**************.com/

sells a kit (with a cable) that basically does the same thing. I can't see from the small picture where it is placed in theline- maybe you can see it if you have a giant monitor?

Pete Burton · #41 07-17-2006, 03:31 PM

Please make sure the hose is a heater hose and not the supply line to the eveporator before you cut anything. It should be soft enough that you can pinch it closed with your bare hand, if that helps.

topanga · #42 07-17-2006, 03:53 PM

WOW WOW WOW WOW WOW

speechless. It's just a trickle, and it's only just barely cool, but I ran the car for all of sixty seconds, so that's what you get. I vise-stoppered that hot line up by the firewall, and I get a wash of not-hot air from the defrost vents and just a tiny amount from the (formerly not-operating) side vents.

(I noticed that the knee vent I was talking about does not vent into the cabin when the door is closed, it disappears into the door. Anyone know why?)

This is AMAZING! AMAZING! AMAZING!

Now I need to figure out how to bypass the servo for now. I agree, I'd like the splice to be between heater core and servo, not servo and cabin, but I don't know how to find it. Can I assume the tube that exits the servo (or, wait, enters the servo) on the OTHER side of the servo is the same line? There are just sooo many hoses into and out of the servo.

I don't suppose it would be a bad idea to get an a/c charge at this point as well.

But as I said: WOW. You guys are amazing. I wish you knew how grateful I am. I'm not out of the HOT woods yet, but... I'm getting there.

I am definitely having a whiskey tonight in honor of guess who, but I'd like to buy you all one.

Pete Burton · #43 07-17-2006, 04:15 PM

Quote:

Originally Posted by topanga

I don't suppose it would be a bad idea to get an a/c charge at this point as well.

Make sure you really need it first. With the A/C operating, there is a "sight glass" - it's literally a little (about half an inch) round glass window where you can look inside your system. If there is a lot of frothing white bubbles churning along, you MIGHT benefit from a charge, but be careful. If anyone you bring it to tells you that you need to "convert" your A/C because freon is hard to get or expensive, RUN, don't walk, away.

The system can be undercharged and run quite well for years. WAY too many old cars have been harmed by A/C conversions, don't let it happen to you.

riethoven · #44 07-17-2006, 04:48 PM

Quote:

Originally Posted by topanga

48 was, yes, WAY, WAY too young. I have to think there was a reason, and it has made me savor life a lot more knowing that it can be brief. If there's one thing I can share with people, it's the importance of early diagnosis and APPROPRIATE diagnoses with cancer. My one piece of key info for anyone facing a cancer diagnosis is: ASK FOR A PET TEST. PET test. PET test. PET test. Accurate staging is EVERYthing. I sincerely hope that this is useless information for everyone and none of you ever have to use it.

Congratulations on cool air! I had BMW 2002's and putting a valve in line to the heater core was a standard modification because the heater valves always let hot water into the heater core even when turned off.

We lost a son to a serious heart defect and I learned everything I never wanted to know about pedriatric cardiology. The worst part besides losing our son was seeing the smiling doctor every day telling us that everything was OK. My mother passed from cancer last year and I my wife and I get screenings once a year.

I will post photos of my regulator repair. Maybe it will help. I drive a W123 which came in a little later than the W116.

rs899 · #45 07-17-2006, 05:22 PM

topanga-

I am home now and took a look at my car. Correcting my earlier statement, I see a couple of places where a valve could be inserted. If you look at the front of the engine- locate the water pump. To the left, there is the heater bypass line just aft of the water pump housing. There is a short length of hose, then a long 18" pipe, then another short hose that leads into the base of the servo ( the aux pump is hung off the side of the servo - forget it). I would place a valve in either of these two short sections of hose leading back from the water pump to the bottom of the servo.

Pete- Don't worry- all the pressure hoses enter the cabin just above the brake booster (making its replacement another challenge).

keep us posted

Rick

Oh - and the heater core is buried in the dash- your valve - if you put it where I suggest - will be between the water pump and the servo.

And- the sight glass Pete is talking about is on top of the receiver dryer which is hung- conveniently in front of the condenser- its that metal cylinder about the size of a beer can that stares at you when you open the hood (behind the grille)