No blower...no heat...no idea how to fix.
 

hello everyone.

For the past few weeks, I have been experiencing inconsistent blower motor operation. No matter what button I pushed on the a.c.c., I would get no response for the first 5-10 minutes of driving. Once it kicked in, though, everything worked as it should.

Yesterday and today, however, the blower motor never kicked in. This, of course, is a huge problem because it's freezing cold outside. I have no idea how to diagnose this one. Let me tell you what I'm working with, and hopefully someone can tell me where to start.

1983 tdt wagon:
-new mono valve
-newer blower motor ( replaced within the past two years)
-a/c does not work---the compressor has been removed
-pushbutton unit seems to work, as it always makes a "shhhh"
noise whenever i switch buttons

Is there some sort of relay that controls when the blower motor engages? Would the aux. water pump do this if it quit working? Any help would be great.

Thanks to all for your time.:)

I'd like to know, too. HATE the auto climate control!
 

.

my motor will only work once the engine temp reaches a certain temp except when i use defrost. then it will always come on no matter what the temp of the motor . if this is you problem then you might have a thermostat problem
john m

I forgot to mention that I just replaced my thermostat 3 weeks ago. That defenitely helped with the heat issue, but not the blower problem.

You must have the sister to my old 81 wagon.... I never knew when it was going to decide to activate the system which I had pushed the button on....completly random as far as I could tell....
I had great vacuum .... could open doors a week after shutting down the engine....
Have you done a search ?.... I think a LOT of good info has been posted on this.... try ' climate control' first...

I had an intermittently working ACC system too. I changed ALL my fuses (most of which were original) and that got rid of a lot of electrical gremlins (the ACC among them) that I was having. Whenever you change your fuses, make sure you get good ones. I bought some at a local parts store, and while they looked exactly like the ones from FastLane, they kept blowing. I bought a whole bunch from FastLane, installed them, and haven't had a problem since (it's been a few months).

Alex

Check the pre-resistance group
 

Hello
Check the pre-resistance group; it is mounted on the right upper fenderwell.

Edit:
Egad, the price$.

Vehicle 1983 Mercedes Benz 300TD Turbo Wagon

Blower Control Switch

Temp Control Regulator, Programa Note: Remanufactured

Blower Regulator, Programa Note: Remanufactured


I would retest the blower motor with a fused jumper wire.
The Blower Regulator Switch, climate control switch assembly or Temp Control Regulator may also be bad, with luck, if it is the Blower Regulator Switch, resistor, climate control switch assembly or Temp Control Regulator, you may get one or all from a U-pick junk yard or a forum member parts car.

Have a great day.

The pushbutton unit is highly suspect unless it's a rebuilt unit, installed in the last few years or so. Mine got worse to where I had to play with the buttons to get the blower fan to start up. A rebuilt unit cured that problem.

Another issue is the fuse. The 25A fuse in the W123 (and 126, I think) is right at the limit for that circuit. It tends to get REALLY hot and either blow the fuse after days/weeks of thermal stress, or if you have cheap plastic fuses, it can melt the plastic body while leaving the metal fuse part intact! Remove the fuse, clean both contacts with a wire brush, and re-install a fresh ceramic-body fuse. Mercedes came up with a fix for this, which is a kit that installs an external fuse outside the fusebox... I think it's a flat style 30A fuse like the W124's use, basically a small version of the 80A flat glow plug fuse. My car desperately needs this fix, I need to order that kit, I'm tired of changing a semi-melted fuse every few weeks... ;)

Note: If the fan comes on but you get cool air, that's a different problem - I'm assuming your fan won't turn on and that is the main issue here... :)


HTH,

Intermittent fan operation would most likely mean you've got a dying blower motor. Mine started making squealing noises then would shut off and come on intermittantly, then after a while it quit all together. Opened up the blower housing to see the bearings were clearly shot as there was a rusty powder blown everywhere.

Hello 190D22
Please repost your wonderful rust picture over in my thread:
Who has the most rust and still drives

A perfect example of rust can happen any place.
Thank you.

Do you hear a click or rapid clicking noise coming from the climate control unit as the fan quits? Mine always made those noises you speak of but when the fan was quiting whenever it seemed like it I kept hearing a clicking noise. I resoldered every joint and pin I could get to and the problem was gone for a month. But since my car was running so hot I had to leave the fan on max for that whole month which I believe lead to a solder failing again, I just resoldered it and it is back up and running but I haven't done much anything with the car in the last few weeks. I just changed the thermostat to a Behr today so hopefully that probelm is gone now.

Hi BoostnBenz.

No clicking noises at all. And once the fan kicks in, it's all set---as if it had worked all along. I have good heat, my car is running right above the 80 mark once it is warmed up. It's just that initial 5-10 minutes that I get no response.

I failed to mention that once the fan starts working, if I drive a short distance and turn the vehicle off, the cycle will repeat itself when I restart the car. But... if I've driven a longer distance, achieve normal operating temp., and stop and restart the car, the blower will ussually start as soon as the car is restarted. So, I'm just not sure. I ordered some new fuses as was suggested, and I'm going to follow through on Whunter's suggestions. I'll post my results.

Thanks for all the help guys!!! :D

Fan does not run until the heater core gets to 40C. In very cold weather, this will take a while.

The sensor could be bad, or loose, too, so that it really has to get hot before the blower comes on.

Should run the blower on defrost, whatever the coolant temp.

If not, the pushbutton unit is probably bad.

Peter

I had similar problems about a month ago.
I took out the ACC unit and resoldered the pins and side PC boards. Problems solved.

Attached a photo of the ACC unit PC Board

Steve
________________
1985 300D Turbo

Here is another picture of the ACC unit


Steve

________________
1985 300D Turbo

Please make crystal clear
 

Hello Steve300
Please make crystal clear, what area you soldered, someone may mistake the area and burn a board.

#2. Please make crystal clear
 

Hello Steve300
Please make crystal clear, what area you soldered, someone may mistake the area and burn a board.

Hmm, I'm not sure about Steve but I resoldered EVERYTHING in sight!!! The most common failure is at the pins, but I also did the main board and where the two side boards meet (probably second most common failure) the center boards. People take burning a board up a bit far.

whunter:

Yes, I resoldered the area you circled with red ink (the solder side of the PC board).
I found 2 traces the solder were broken. This ACC unit PC board's design is very bad. It uses solder to connect 2 side PC boards to the main board. After close to 20 years of pushing on/off the buttons, those solder traces bound to break lose.

Well, at least it is repairable. You don't have to spend $200 to buy a rebuilt one.


Steve

I FIXED IT!!!!!!!!!!!!!!
 

:D
I bought all new fuses as suggested, replaced the old ones, and nothing happened. It was a good starting point, though.

Finally today, after re-reading all the threads and misc. info on soldering the guts of the acc, I pulled the unit out to give it a try. Get this---my mother-in- law and I repaired it together, and it was no problem. Popped it back in when we were done, and all the buttons now do everything that they're supposed to.

Thanks to everybody for the advice and help. Another success story! If my mother-in-law and I can do it, anyone can! ;)

Do you loan your mother in law out ?

Good job, DIY. Re: I FIXED IT!!!!!!!!!!!!!!
 

I am impressed.
A triumph for DIY.

I have this same problem, and while I'm good with electronics, I'm a novice at mechanics. The ACC (Automatic Climate Control, I'm guessing), is that the thing behind the glove box? If it's what I think it is, my benz CD manual calls it an "electronic unit for blower speed control". The wiring diagram shows the push buttons being connected to it, and it's in turn connected to blower resistors and the blower motor.

Just to reiterate the problem, the blower comes on randomly. Sometimes (very rarely), it'll work perfectly, from when I start the car to when I stop it. Most of the time, it won't come on at all. Sometimes, it'll come on, then stop after a few minutes. Sometimes I'll leave the switch on, and it'll cut on a little while into the trip. When that happens, sometimes it continues working, sometimes it shuts off. I've been trying to find a common link between all the events, but so far, nothing. It seems to be independent of outside temperature, of engine temperature, of me messing with the buttons, etc. Although, about 50% of the time, if I keep pushing buttons at random, it'll come on after a while.

no heat at all, blower fine
 

I see the replies for blower trouble,
mine is fine.
Just no heat, ever, not even on defrost.
Can anyone help with that?
Thanks

The ACC, CCU, or whichever acronym you use is just a fancy name for the thing you are pushing the buttons on. It is right above the radio. The electric speed controller you're talking about generally doesn't go bad but it is in the engine compartment on the passenger fender (the thing with the coiled wires inside it). I bet your climate control unit just has a few bad solders in it.

Thevegmyster, I don't know how it could "never" have heat but if it has it only at slower speeds then goes away as you drive faster that'd be a bad monovalve. If it is parked in the sun a lot then perhaps the foam tube that brings the air down to the temperature sensor is bad and is pulling in warmer air than that in your car. I suppose it is possible that the temperature turn switch could be bad, but I've never really heard of this type of failure.
^Edit^ Does your auxillary water pump work? If not it may be getting in the way of the coolant trying to make it into the heater core to give you heat. If you have the ignition on but car not running do you hear the little motor running? Adding an inline fuse to its power wire would be a good idea, because a bad aux pump can lead to a bad CCU.

Thanks, BoostnBenz,
There is never, ever any heat at all, even at freezing midnight.
You are right - there is no sound of the aux pump working!
AAAK! Now the bottom of the servo leaks at times.
I wonder if I ruined it...

Servo? the climate control leaks?! What is coming out of it? There is no fluid inside of it! Something must be going through it then. If something keeps leaking on it, it will ruin the unit eventually.

This is a classic case of why you should put your car's year and model in your signature. If thevegmyster's car is a 1980 300SD, then it would have the climate control servo in the engine bay.

This is true....

Sorry folks,
you are so right about posting model of car.
Thanks for your responses.



'80 300CD
non-turbo but GOES!!

So I took out the ACCU and resoldered the parts where the solder keeps the two board together. It worked great for the first three times I started the car after that, then I let it sit for a few hours, and went out again. This time it didn't work. I made 3 stops, and restarted my car 3 times, and it didn't work any of the times. On my way back home I remembered something about someone getting it to work by hitting the wood panel in front of the ACCU, and I did that, and the A/C came on.

Any ideas?

Yea I used to hit it as well. I went through and resoldered everything, it fixed all the problems.

I was gonna resolder everything, but I don't see the point. I mean, I understand why the sides would need to be resoldered, because all the stress from 20 years of the buttons pushing that board would break the solder joints.
What I don't understand is why the regular solder joints would go bad, and more importantly, why hitting the ACCU would make it work. That second one especially boggles my mind.

Because internally one of the solders have broken free but don't always make contact. It sounds like you have the exact same problem I had, perhaps you may think it'd be pointless to resolder all of them but it fixed mine. I was told that over 50% of failed CCUs fail in the pins on the side of the CCU, the rest is normally where the buttons are soldered onto the boards and the others are where the side boards meet.

Just to wrap up the thread... I resoldered almost every pin on the ACCU and the A/C has worked great for 3 days now. I found a few cold solder joints on the boards, and I'm guessing that's what was the problem. Thanks everyone.

I had similar symptoms... was a combo of Monovalve, blower motor. and cold solder joints on climate control unit (I had em' all).

RepairFlix has good videos on monovalve repair, climate control repair, etc. If you buy direct from his website and not through ebay he will combine shipping on multiple videos.

http://www.repairflix.com/cart.php?cat=Misc+Mercedes+Procedures

Scroll down to "Climate Control Computer Repair"

AND...

The blower motors are expensive, but very fixable... brushes need to be replaced. Easy
Mercedes Source has a manual including the brushes which fixed up my 1982 300D blower motor. Mine also was intermittant.

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

Description of the kit (Manual only also available)- (BTW, Fastlane doesn't sell these brushes...)

123/116 Heater Motor Repair Kit
Item # MRG-123HMR

For all 123 chassis cars made from 1977 to 1985 and all 116 chassis sedans built from 1973 to 1980.
This repair guide will take you through the process of how to properly remove your heater blower motor and replace the motors two brushes. This is the most common reason for failure. If your blower motor has been intermittent or some days it won't come on until you drive for a while your motor brushes are most likely at the end of their life. This is something you may just want to replace as a preventative measure. 20 year heater motor brushes are very prone failing at any time. If it has not failed yet it most likely will sometime soon. Along with this detailed instruction guide I will provide you with a set of new brushes (which I have diligently sourced). You will need a soldering iron and a few common hand tools to complete the job. If your car has a over 150,000 miles on it or you know the heater motor has been run a lot, the best time to do this job is now! Don’t wait for it to quit on you on a cold winter morning.

PS... congratulations on tackling the fix yourself. THIS BOARD IS GREAT!

Climate Control Switch
 

I've been reading all these post and my what complications of the heating and a/c units of these MB's. Well in the winter my heater wouldn't work until i drove it about 20 miles. It starts a clicking noise under the dash on the passenger side. Does this for about 5 min. then MAYBE my heater will come on. Now that Spring has arrived and I use my A/C some. The A/C works fine, but when i get out of the drive the clicking starts up again and does it for about 5 min. Is this the climate control that's making this noise? Where is it located exactly? What is the cost in repairing at a local MB shop?

You have a bad pushbutton unit. Shop is gonna charge a couple hours labor and about $300 for a rebuilt PBCU, $500 or so for a new one (they will charge list price).

Peter

Blower Motor
 

Worn brushes in the fan motor can cause mysterious symptoms. After dismantling/checking/resoldering most under-dash components to no remedy, I pulled the blower. It seemed to run fine on the bench, but was still intermittent in the car. Replaced the brushes with some I picked up at the vacuum cleaner repair shop for a buck each (sandpaper to fit) and everything worked geat. - Jacob

am I retarded?
 

I have the CCU out, on my workbench, all of the buttons removed, the bottom cover off, but I do not see how it is possible to get the plastic cover off to access the top without breaking something. Does it just require alot of force, or is there something obvious I am missing.

fyi -
1985 300DT. This whole fiasco started when things went from good to "hot only on defrost". Upon inspection, the hose for the temp sensor had, predictibaly, deterioriated. I put the dash back together, but now the heater fan does not work, even on defrost. High - Low ALWAYS worked before, but the center vents have never worked. I assume that the CCU needs to be resoldered, but how to get at it without shattering it to a thousand pieces?

Have you used the climate control test sequence in the FSM yet? I found it to be extremely helpful.

Maybe this will help.

Blower motor
 

The commutator (copper thing the brushes ride on) on my blower motor was so worn that there was no point replacing the brushes. I was surprised the motor still worked at all. I shopped around and found the best deal to be ******** Arizona, $85 for a new motor and free shipping over $50. The motor is here, it's a new Bosch, just like the old one. All I have to do is press off the fan, put it on the new motor, and be good to go...after I resolder the ACC board of course...having already kitted the mono valve.

The re-solder job, by the way, is the same procedure recommended for the cruise control brain, and works just as well, at least it did for me.

Jeremy

link please
 

I haven't found this - link please

I found my intermittent problems were caused by bad contacts in the ignitions switch. Jiggle the switch and the blower comes on. Might be repairable but I'm going for new replacement.

The problem is the blower motor runs .. but no air comes out of the vent.

I am having the same problem. I just purchased my 84 300SD and it never worked since I purchased it. I can feel the heat or the a/c coming out of the vents but no blowing action. Can anyone help. Next, if you can help, i dont know where any of the parts are to fix. THanks

Now that I took my wife's car apart....
 

I too am having a major AC problem. We have a 1991 350SD with 80K. A few weeks agao, the AC was not blowing. Then, out of the clear blue sky, it started right up. Today, my Mother in Law started the car (I say she did it) and the AC was not blowing. I pulled the car apart, and checked the blower motor. It has power, and I bench tested it real quick, and it clicked over (did not do it long enough to make it turn. I then took apart the rest of the car...thinking it was the fan switches with a loose conenction...NOPE! My brother in law sent 12V to a pink wire that plugs in to the rear of the Temp Dial. The Blower motor clicked each time he touched the power..but never actually turned.

Can this be the Brushes everyone is taking about? I live in So Cal, and it has been really hot..the wife is not happy....Help...:confused:

Re-test
 

the motor on bench.
You must run it up to speed.
Be sure the motor bushings are well lubed, and NOT sticking/binding = spins free by hand.







Have a great day.

Ok...my blower motor spins freely, and the brushed seem to be good and making contact. When I say freely, it does not spin on its own, and needs asssitance, but it spins. I decided to put the blower motr back in and plug in the Blower Motor Regulator "porcupine". I turned on the AC and the blower motor was working fine..the air volume was low, but that is becasue everything was open...When I had the fan speed on Auto, the fan turned fast, on low, turned low (barley moved) and on high it turned fast.

Once the porcupine warmed up, the fan speed got slower and slower. Then finally the fan stopped turning...and the porcupine was super hot..could not even touch. My thought is the Blower Motor Regulator is bad? Help...any ideas, thoughts...anyway to test that or bypass it to test the fan?

There are 3 wires on the regulator-think pink wire, a thicker guage brown and a thicker guage green.

Help..need ideas..thoughts...Thanks...:confused: