I've dealt successfully with my 81 300D and its blower motor, but am now working on my son's 77 300D that has a vastly different control system. Taken out of the car, the blower works great. No response when in the car. Is this a model with the 'evil servo'. I've never run into one before, but this system looks way complicated.

Is there anything relatively simple I should be checking to get the blower motor functioning again?

__________________
Erlend
1981 300D 202K daily driver

Yes, it has the evil servo if it is a US model. I posted a link to a copy of the manual for the servo system. Search on my name and servo maual to find it. I also have a thread about the blower motor in my 116SD that you might find helpful. There is a central vacuum cut off switch that won't allow the blower to work if there is inadequate vacuum or the switch fails.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

anyone know where this switch is?

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

On a 79SD it's behind the glove compartment. The manual shows it.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

its behind the dash.

Blower motor is controlled by the servo and the blower vacuum switch.

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

I looked but couldn't find it. I want to by-pass the electrical connection.

__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg

No response even in high defrost? It makes a difference when it comes to troubleshooting. That blower vacuum switch can go bad on your '77, and it will still operate the blower in high defrost, because someone was smart enough to realise that defaulting to defrost was an important safety measure.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

it wont operate if you have a vacuum leak.

__________________
1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Without vacuum to anything to anything in my '77, defrost high works. The service literature I have read indicates that is how it should function without vacuum, but with everything else in place and operable.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

My beloved 78 300D has finally joined the club of those who had relied on High Defrost as their only heat source only to see it fail. The PO had paid big money to have all the guts replaced, and I have receipts, but before I bought it the only thing working was high defrost. Just this week that has stopped working too.

Is this vacuum switch my likely problem? If it had failed and left me with only high defrost, then what else failed to leave me with nothing? I haven't even checked fuses yet, but I figured it's about time I launch into getting this darn thing to work properly, if humanly possible.

Any leads or link references would be appreciated. Thanks.

__________________
Where there's a will there's a way
1978 300D

Check the fuses, first. A quick glance at my notes indicates that fuses 5, 10, 12, and C are all in use when in Defrost mode. I don't know what does what, because I neglected to right down fuse designations, and my notes are pretty useless even to me without staring at the car, because it's been over a year since I touched the climate control system.

Some of those fuses are obviously going to be for the AC side of things. You can safely disregard those particular fuses while working on getting just the defrost function to work again.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

I replaced the servo on my 77 300D with the digital box from unwired tools, fixed all of the problems. Cost is a little much but overall it is best.
Ron

There is a box behind the glove box that assist in the control, it will fry along with problems with vac and the ccu, the digital box bypasses this sturr and just works.

Wiser words have probably never been spoken about the ACCII system. I've never heard an owner of an Unwired Tools conversion speak anything but praise for them. I gave up on dealing with the ACCII system because I value my sanity, and figure that dropping $700 on the trouble-free conversion will be a lot less of a hassle than the hours and hours it would take to repair the original system. It will very likely pay for itself several times over after a few years of ownership, given the unreliable and expensive parts failures of the original system.

The entire ACCII system is a pile of junk that should never have been allowed to disgrace any Mercedes-Benz. What ever jerk was responsible for implementing it is guilty of a crime against humanity, or at least the humans that ended up owning a car equipped with it. Many of us would be grabbing torches and pitchforks if we knew who was responsible.

You say you have receipts for the recently replaced system components. How about selling them on eBay to recover some of the cash outlay it takes to get Unwired Tools conversion? Recent receipts for parts make them worth much more to the typical eBay bidder.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

Unwired tools? Sounds ideal. Never heard of it but then again I am just getting serious about having this system work. Is there a DIY for it somewhere or do they provide directions? I'll check fuses today, just to eliminate the obvious. Then, honestly, if I could do a $700 fix for a solid state solution to my climate control that would give me all my heat functions then I would do it in a heart beat.

I've read countless posts about the evils of the climate control system on my 78 300D and know the current system is a cruel joke on an otherwise bullet proof car.

Here in the PNW it is cold 9 months of the year and I even plan to disconnect all the A/C just to save 1/2 HP. But man, we need heat. Just like another guy said on another post, the wife is almost refusing to drive the Mercedes since she has some silly notion of liking her car to be above 38 degrees.

I truly appreciate the advice and help from this forum. Thanks.

__________________
Where there's a will there's a way
1978 300D

Wow, I just googled unwired tools and that sounds perfect. I love the whole concept. I'd like to hear from anyone who has actually installed one of these guys on their W123 300D to see what the battle stories are.

I have an uncle who is an old electrical engineer who has made a good living fixing and redesigning microwave telecommunications equipment for ATT and the big players. Like this ACCII crap, people do crazy stupid stuff with microwave equipment and there is often a more elegant and effective solution. Anyway, from this I have great appreciation to people and companies who actually prioritize simlicity, reliability and elegance. Like the old story of russians using pencils instead of NASA trying to get a pen that writes in zero G.

So any veterans of the unwired tools conversion willing to encourage or discourage that route?

__________________
Where there's a will there's a way
1978 300D