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.

__________________
1984 300TD Wagon--Astral Silver--Retired
1983 300TD Wagon--Dark Blue--Retired

.

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.

__________________
1984 300TD Wagon--Astral Silver--Retired
1983 300TD Wagon--Dark Blue--Retired

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

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

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.

__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

https://www.boldegoist.com/

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,

__________________
Dave
Boise, ID
Check out my website photos, documents, and movies!

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.

Attached Thumbnails

 

__________________
1984 190D 2.2 Auto 220k
2001 Jeep Cherokee Sport 70K
2004 Lexus RX-330 ??K
2005 Chrylser Crossfire LTD 6K

Play guitar? Go to www.cyberfret.com for free online lessons!

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.

__________________
Jeff M.
Mercedes W123 DIY pages are now located here.
1983 / 1984 300D Sold
2000 CLK430 Cabriolet ~58k Sold
2005 Avalanche 4x4 ~66k

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!!!

__________________
1984 300TD Wagon--Astral Silver--Retired
1983 300TD Wagon--Dark Blue--Retired

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

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

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

Attached Thumbnails

 

Here is another picture of the ACC unit


Steve

________________
1985 300D Turbo

Attached Thumbnails