Power windows and blower fan stopped working
 

Oh no, electrical!!

Last night when I headed out, the Defrost would not come on. I 'rebooted' (shut off and restarted car) and it worked for 3 seconds, then stopped. Since then, nothing.

Now when the ACC is on heater, it was sometimes intermittent, but the defrost ALWAYS worked. I also noticed today that my power windows do not work, none of them.

I have checked and replaced the fuses and no luck there. Do this sound familiar to anyone?

Thanks for the help, and happy holidays

Bootsy

which model?

Sorry, 1983 300 D

I assume that when you say "won't work," you mean that the fan won't come on. This could be a bad ground somewhere -- that's about all the climate control system has in common with the power windows. The windows, especially since they are on two separate fuses, usually don't go bad all four at once. A semi-bad ground will keep high-current loads (blower fan, window motors, etc.) from working but allow low-current loads (instruments, small lights) to still work. That makes the problem harder to diagnose. Anything else not working?

Mercedes has a number of ground points built into the car. One is behind the gauge cluster, there are a couple under the hood, etc. I think the electrical part of the FSM shows where they all are.

Bootsy, if you will go to the User CP and set up a signature line for yourself, you can add your car and model number so you don't have to repeat it on every post. You can also put in your location, if you wish.

Jeremy

Jeremy,

Yes, the fan does not come on, but when I hit the buttons for the other functions like heater or defrost, I don't hear anything moving (flaps, whatever), so I don't know if it is JUST the blower.

I just checked the grounds behind the cluster,; there sure are a lot of 'em, but it looks good, no corrosion, nice and tight, no (obviously) broken wires.

And yes, ALL the power windows don't work...

Any other grounds I should check? Is there something I should do besides pulling on the wires to make sure they are not broken?

Thanks

And it seems like everything else electrical does work. (wipers, flashers, lights, etc.)

Further diagnosis....
 

This might be two separate problems that occurred at the same time by coincidence (windows and ACC). Coincidences happen all the time, although we must always be suspicious of them, in case they do turn out to be related somehow.

If the fan and flaps both do not work, the problem is likely electrical. I don't remember whether the '83 has the latest version of Climate Control or one of the older versions -- perhaps someone else can help here. The flaps are controlled by vacuum actuators and the actuators by the ACC controller, which is electric, so both must work.

If nothing works, then the ACC controller is not getting electricity. You checked the fuses but there could also be a broken wire or (more likely) a failure of the Climate Control electronics (the thing with the pushbuttons). The ACC controller also needs vacuum, which comes from the engine-mounted vacuum pump. If the power brakes work, then the vacuum pump is OK but there could be a broken or leaking vacuum line somewhere, especially given the age of the car.

Defrost is the "default" for the Climate Control system -- the rationale being that getting hot air to clear a fogged or iced window contributes most to safety. Even if all of the vacuum flap actuators fail you should get hot air onto the windshield if the ACC controller is getting electricity.

The Climate Control system includes an auxiliary water pump, which assists in getting sufficient hot coolant into the heater when the engine is turning slowly (as in city traffic). Unfortunately, Mercedes failed to fuse this little (electric) water pump; if it freezes, it draws too much current and damages the printed-circuit wiring in the ACC (pushbutton) module. Rebuilt modules are available (I was able to repair my own) and everyone is encouraged to add a fuse to the aux pump circuit to prevent a recurrence of this failure. The later (W124) cars have a current-limiting circuit built in to prevent this problem.

You can test the ACC blower separately. Remove the passenger kick panel and you will find the blower up underneath, with a two-wire black plastic plug and cable. Remove the plug and put 12 Volts directly on the motor terminals to see if the blower will work. The blower is held in with three screws and is fairly easy to remove.

As for the windows, there may be a ground in the area of the console where the window switches are located. You can lift up the panel with the switches to check on the ground. If you have a voltmeter, you can also see if the switches are getting 12 Volts.

To remove the window switch panel, you must remove a screw or screws located at the front or back of the panel (I don't remember which year-model has which fastening). To get at a screw at the back of the panel, you lift up and remove the little piece of carpeting that lives at the bottom of the tray. To access the screws in front, you remove the ashtray. With the screws out, you can pull the panel back and up gently.

Jeremy

Check fuse #12- REMOVE THE FUSE to check it and then change it even if you think it's good. I'll bet your turn signal don't work either, but they will when you change that fuse.:rolleyes:

Jeremy,
re: the ACC. Actually, I do have a vacuum leak in the door lock system, If i leave the door unlocked there is not enough vacuum to shut the engine off. Once I lock the door, the engine will shut off. So I will re-check whether the vacuum flaps are working when I get it up to full vacuum and report back.

MTUpower: I do have turn signals, but I will change #12 (If I haven't already)

fuse #12 powers the window relay among other things.

Replace ALL the fuses
 

Not just #12, but all of them. Get the new copper kind. The regular aluminum ones pit and cause electrical resistance, which builds up heat. They might look fine, but can cause problems. Get rid of all of them, replace all of them. Cost you $8 or so.

jeff 1991 300d

Well, I changed all the fuses and no change in power windows or ACC.

With full vacuum (enough to shut the car off, don't know if leak would effect this) I cannot hear any movement in the ACC when i switch to different modes.

I guess the next step re: the power windows and ACC is to open up the console and take a look and see if they are getting power....

On the plus side, while looking at the grounds behind the instument cluster I changed the dash light rheostat thing and have dash lights for the first time in a few years! (very easy if you haven't tried it, been putting it off for a long time..)

small steps....

Merry Xmas

Ho Ho Ho
 

And Merry Christmas to all from snowy but bright and sunny Salt Lake City.

The ACC pushbutton thingy is easy to remove. The wood cover is simply held on by four plastic snaps. Pry carefully and it will pop off. Next, remove the two Phillips flat-head screws in the upper corners of the pushbutton module. That releases the top of the module.

The bottom is held in by fingers molded into the plastic. You must lift the module up while carefully pulling the top towards you (for clearance) until the fingers pop out at the bottom. I found that I could use a flat-bladed screwdriver in one of the slots in the plastic panel of the ACC.

Once the ACC pops free, you can pull it out of the dash enough to see the cables on each side and the string of lamp wiring. Unfortunately, I don't know which pin on which of the two cables delivers power to the ACC. It may in fact be getting power but simply not working. It's strange that the defrost mode (at least) does not work. Mercedes designed it to be the last to fail since almost nothing needs to work for defrost to operate.

Have you tested the blower yet?

Jeremy

Now with pictures
 

I have not tested the blower, but it is not getting power, so I took out the ACC. The ACC was getting power on a few different pins, so I opened up the back and it looks burned in a few places. See Photo. Is that what it looks like when its fried?

That doesn't look good, but don't know if that's your problem. An expensive swap out. The solders appear to be OK, I was going to mention to check those. That unit has a high failure rate.