1980 W123 Defogger fan motor - PeachParts Mercedes-Benz Forum

turbozeke418 · #1 03-15-2013, 02:29 AM

I have a 1980 300 TD and the A/C system has never worked. The electric fan works though blowing out heat for the defogger system. I have read because that is wired independent of the regular HVAC system. Just recently it stopped working. I can feel heat trickling out of the defogger vents but it won't blow. Where should I look first to troubleshoot this?

Diesel911 · #2 03-15-2013, 11:07 AM

Quote:

Originally Posted by turbozeke418

I have a 1980 300 TD and the A/C system has never worked. The electric fan works though blowing out heat for the defogger system. I have read because that is wired independent of the regular HVAC system. Just recently it stopped working. I can feel heat trickling out of the defogger vents but it won't blow. Where should I look first to troubleshoot this?

Check The Fues first; remove it and inspect the tips and contact area and the Bracket.

If the Fues is burned when these Motors get old the lubricatin drys up and they also get full of crud. That extra load causes it to pull more Amps and blows the Fuse.
The Motor Brushes can also wear out. If you havea Bosch Motor there is a Do-it-yourself on that but I believe it is a Motor from a W116.

Remove the Right side Kick Panel and you will see the Motor. Trace the Wire and dosconnect it from the Blower.
At that point you can use Jumper Wires to the Battery to test the Motor itself or you can probe the Wire side connector with a Meter or 12 Volt Test Light to see if you are getting Voltage through the Wires to the Blower.

Not all of the Motor Housing setups are the same.
Also the Bosch Motor has the Brushes in the rear and on Mine I have a Seimans Motor with the brushes in the front.

the pic is what my 84 300D one looks like when the Kick Panel is removed.

cooljjay · #3 03-15-2013, 01:28 PM

First you have the evil servo unit...

Second your motor is froze and it blew the fuse. The fuse for this system is in the drivers side fender well, pop off the block box plastic housing...you will see 2 relays...next to the relays you will see a fuse holder...twist that open and there is a fuse....when you replace the fuse, clean the contacts.

The fan motor is located as stated above. You can remove it and disassemble it...I couldn't disassemble my motor, instead I cleaned it with carburetor cleaner and then oiled the motor....to confirm it is the motor...you can tap the bottom and it should start up again.

Now to get your evil servo working again, you need to unfreeze the auxiliary water pump next to the servo under the hood....remove the glove box liner and replace the computer and sensor tube...this is he minimum that needs to be done.

turbozeke418 · #4 03-16-2013, 12:57 AM

No fuses are blown...The blower is barely working. It used to blow out fast and now barely blows. I'm assuming its just old and needs to be replaced. As for the servo...I gave up on that years ago and use the defog/defrost electric motor to heat the car in the winter. I'll pull the motor and troubleshoot soon. Thanks for the input.

starrywhite · #5 03-23-2013, 02:49 PM

Mercedes W123 Blower Motor Solution

I have tried to repair two Bosch motors, one a 79 and the other an 83. Replacing the brushes is easy, even though the 79 motor had to be broken open and re-crimped.

Both worked for a while, until I realized that those commutators were just too far gone, even though they had the appearance of being ok. I tried shifting the position of the brushes to bite on unworn areas, but again it was only a matter of time before the motors stopped working.

There are a couple of alternatives.
One is a full-blown commutator repair, as found on a quick web search for “repair commutator”, and it looks doable, by soldering a copper sleeve onto the old one once it has been worked down evenly on a lathe. One would have to use high heat and non-lead-based solder.
Then one has to cut grooves and do some polishing on the lathe.
One day I might still try this method.

Another is to find a reasonable 12-segment commutator on an 8mm shaft and swap commutators. Most Japanese blower motors have 8mm shafts so this is also doable. Or one could try and do an armature swap once a suitable match is found. This may be time-consuming. Rumour has it that some Volvos also have similar Bosch motors, but I do not have the time to go searching.

The method I have settled on for both my wagons, is to make an adapter plate and fit newer blowers found on whatever you can find at your local wrecker. I have two successful transplant options. One is from an Isuzu Rodeo and the other from a Nissan Pathfinder, both from the mid-90’s. Both have squirrel cages more or less the same size as the original Mercedes. The Isuzu squirrel cage is slightly smaller but there is no perceived difference in how well my windshield defrosts. The motors will protrude a bit further than the originals but this is not a big deal. The kickplate will still screw down adequately. The Pathfiner’s is the one I’d recommend.
The benefit here is that it takes a short time to find such a motor, and the work needed to fit it is not too difficult or time-consuming. We don’t necessarily do this to save money, but I paid $30 each for the motors.
The trick is to make a cardboard template of the Mercedes housing that reflects the position of the squirrel cage relative to the outer circumference of the housing that bolts to the dashboard. It is offset and your adapter plate has to compensate for it.
You will figure out how to make your template. That is the hardest job. I cut a rough inner circle in a carboard disk. Then I cut the ring open at one end so it could fit over the squirrel cage. On the one side of the cardboard, draw the Mercedes housing circle. On the other, the squirrel cage outline. Tape over the cut to close the circle and have fun cutting out with scissors. The final product doesn’t have to be of Swiss precision.
Next is to transfer the outline of the template onto some 1/8” plywood of good quality, or some aluminum plate if you have the patience to do drilling and filing. Perspex might also be a really good alternative. I have a scrollsaw so cutting the plywood took 10 minutes. At one point the plywood is going to be very thin, so work carefully.

Now you must decide how and where to bolt the plywood to the fan housing and to perhaps glue the plywood to the plastic, but I am ignorant of the kinds of glue that would do that. Epoxy is not the greatest for plastic. I have anchored the new housing to the plywood by drilling small holes and using half a dozen small self-tappers.
I was only able to bolt the new housing to the wood in two places out of the three found on the Pathfinder’s housing, but that has not posed a problem, and after years of driving without a kickplate, the fan hasn’t dropped out yet!
Use the pin adapter of the old Merc fan to connect the wires that plug into the new motor. Giggle when your face gets blown full of dust on the first blast.

Diesel911 · #6 03-23-2013, 04:08 PM

Mine had a Siemens Motor instead of a Bosch. The Brushes were up front under the Squirrel cage and they were Bronze Brushes instead of Carbon.

In My case I found a corroded connection and a blob of Solder cured that. I also cleaned out the crap inside the Motor and Lubed the bearings by letting 3 and 1 type Oil soak into them for several days.

charmalu · #7 03-24-2013, 12:00 AM

Rumour is correct, the Volvo motor will work. Info in this thread.
http://www.peachparts.com/shopforum/diesel-discussion/305936-everybody-better-take-care-their-123-blowers.html

This post is a DIY article on installing a new Volvo motor.

http://www.peachparts.com/shopforum/2940243-post87.html

Charlie

starrywhite · #8 03-25-2013, 04:21 PM

That's good to know. Endless possibilities.

One more thing worth noting is that the Pathfinder's motor with its plastic sleeve fits nice and snugly into the 83 Mercedes motor housing, so if one trimmed off the flange, that would be a further option. That motor also is anchored with a bolt at the back which is useful.

The 79 Merc housing took a fatter motor. I have the dimensions if anyone is interested.