Replaced AUX Water Pump Fan still doesn't work - PeachParts Mercedes-Benz Forum

Michael_Vila · #1 12-11-2009, 08:45 AM

So, I replaced my Aux Water Pump and Thermostat in my 1987 300D Turbo, alas, no instant fix of the blower fan in the cabin.

What's next on the list? The mono valve? Should have I replaced that at the same time?

Help!

Brian Carlton · #2 12-11-2009, 09:29 AM

Is there some connection between the auxiliary water pump and the blower, or the thermostat and the blower, that we're not aware of?

Graplr · #3 12-11-2009, 09:32 AM

Quote:

Originally Posted by Michael_Vila

So, I replaced my Aux Water Pump and Thermostat in my 1987 300D Turbo, alas, no instant fix of the blower fan in the cabin.

What's next on the list? The mono valve? Should have I replaced that at the same time?

Help!

Not familiar with your model, but as Brian states there is no connection between the pump, thermostat and blower.

If your blower isn't working, the options are-
Bad blower
Bad blower resistor box (forget the actual name for it)
Bad push button unit
Bad wiring/voltage

If it were me I would start by measuring the voltage at the blower and then go from there.

rrgrassi · #4 12-11-2009, 10:38 AM

Did the blower work during the summer?

I know that the om617 has a thermal switch that closes when the engine coolant temp gets warm.

toomany MBZ · #5 12-11-2009, 11:20 AM

I'll agree, those items are not connected, you may have a fuse issue or a failed CCU.

Jeremy5848 · #6 12-11-2009, 11:56 AM

The '87 300D does not have a "resistor box," it has an electronic controller and it rarely fails. If the blower does not work at all (the best test is probably the Defrost button, far left button in the row of five, this forces the blower to full speed) then you first need to make sure fuse #12 or its external replacement is not blown or otherwise damaged.

If the fuses are OK (don't just look at them, actually remove them, clean them, put them back) then the blower itself may be bad. Unfortunately, the blower in your car is buried under the windshield wiper, which must be removed first. The electronic controller is under there, too. It's not difficult, takes no special tools, just some time to remove the trim and water channels, then the wiper, then you can get at the blower. The blower could simply be worn out (brushes, commutator, bushings) after 20+ years. You could also have a broken wire/corroded connector or short circuit somewhere.

If the blower checks out OK, then the pushbutton unit (PBU) is possibly at fault. Rebuilt units are available on-line for $200-300. You can also rebuild it yourself if you are handy with electronics.

Jeremy

hanno · #7 12-11-2009, 01:34 PM

You can test both the blower and the regulator with a voltmeter without taking anything apart. Search this site, its all there waiting for you: ground, +12V, and control voltage. Use same meter to verify the fuses, looks don't count in this application

Michael_Vila · #8 12-11-2009, 02:28 PM

Still working on this. Here's my update; after driving around this morning. I got HEAT! Unlike before. My engine temp is actually registering between 80 and 90, before it barely made it to 80. The blower did not work until after the engine was warmed up and then turn off and back on again. I'll test the Regulator and Blower Voltages tonight after getting home.

Otherwise, it's still a "I hope the fan works today" situation.

Graplr · #9 12-11-2009, 03:25 PM

Quote:

Originally Posted by Michael_Vila

Still working on this. Here's my update; after driving around this morning. I got HEAT! Unlike before. My engine temp is actually registering between 80 and 90, before it barely made it to 80. The blower did not work until after the engine was warmed up and then turn off and back on again. I'll test the Regulator and Blower Voltages tonight after getting home.

Otherwise, it's still a "I hope the fan works today" situation.

You could have had some air bubbles in there from replacing the thermostat and aux pump working themselves out.

Also, how is your driving? By that I mean a lot of stop and go or freeway? My SD has trouble holding 80C if I idle in the cold (by cold I mean maybe 15F and below) for any amount of time. Once I get on the freeway it climbs back up. Also, what is the length of the drives. It takes awhile for the diesels to warm up.

But again, the blower malfunctioning is not related to any of this.

Michael_Vila · #10 12-11-2009, 04:26 PM

15 minutes. That's my morning drive, and it's warm about half way there. I had the same experience, at highway speeds, it constant at or below 80 (prior to Thermostat replacement), I'm going to take the highway home this afternoon to check that. I usually take surface roads to the office, some stop and go, but most around 35 mph. This is my REALTOR-mobile so I need for this thing to be constant!

whunter · #11 12-11-2009, 05:53 PM

Quote:

Originally Posted by hanno

You can test both the blower and the regulator with a voltmeter without taking anything apart. Search this site, its all there waiting for you: ground, +12V, and control voltage. Use same meter to verify the fuses, looks don't count in this application

This blower is known for accumulating dust/dirt in the motor bushings = binding the shaft = locking the motor.

* Remove the blower.
Step #1. Lubricate the bushings with sewing machine oil or ATF.
Step #2. Hold the motor firmly while someone uses jumper wires to spin the motor up to speed.

Repeat steps one and two as needed, until it spins freely..

Links to help you access the blower..

MONO BLADE VERTICAL parked windshield wiper
http://members.lycos.nl/mbenz/windshield_wiper.htm

Hesitating Wiper Repair
http://202tech.mkosonen.com/howto/wiper.html

Can you lube a single wiper mechanism??
http://www.peachparts.com/shopforum/showthread.php?p=150630

Blower Motor Links Page
http://www.peachparts.com/shopforum/showthread.php?t=212324

Have a great day.

psfred · #12 12-11-2009, 10:52 PM

You will need to test the blower motor, the heater core temp sensor, and the PBCU to find out why you have no fan. Intermittent blower operation can be any of the above, but is most likely the PBCU -- I had a bad one on my "new" 300D I had to replace.

Expect to replace the blower motor eventualy, they do wear out. I'm going to do this in the spring, hoepfully, when I replace the evaporator (yuk!) if the blower lasts that long. It's not possible to properly replace the brushes on this motor, and usually the bearings are fried as well.

Peter

Michael_Vila · #13 12-19-2009, 07:17 PM

I've replaced the Regulator. The Motor Works fine. I had it hot wired to a 2 pole switch with an inline 20 amp fuse, but that finally gave up.

I'm not sure how to test the temp sensor, of the PBCU? Any one care to send me information about these?

My email is michaelvila@gmail.com I'd really appreciate it.

The bushing on the motor axle have been saturated with ATF, that seemed to help the fan start right up (When it worked)

Jeremy5848 · #14 12-20-2009, 12:57 AM

Temperature sensor or not, you should be able to get the fan to work on its highest speed by punching the lefthand button (defrost) in the PBU. That is supposed to deliver full heat to the windshield and is the "default" state of the climate control system. If that does not work, there is probably something wrong with the circuitry or one of the relays in the PBU. The temp sensors are usually reliable -- they are just heat-sensitive resistors with no moving parts (nothing to wear out).

There are five temperature sensors! One is in the water jacket of the engine, one is in the air box (heat) and another for a/c, one is in the dome light module, one is outside. Except for the coolant temp sensor, all show in the schematic as variable resistors, meaning they are probably thermistors, heat-sensitive resistors. To test them, you disconnect the plug that attaches them to the wiring, put an ohmmeter on the two pins, and then change the temperature somehow (fingers, heat gun, ice cube, etc.) and watch for the resistance to change. The FSM probably gives the exact resistance but the most important thing is for it to change with temperature changes. Open circuit or short circuit means a bad sensor.

It might be possible for a broken wire or bad connection at one of the temp sensors to be causing your problem. Sixto did some write-ups with pictures on replacing vacuum pods in the 124; he showed the temperature sensors in the pictures, I believe. You should be able to get at them from under the dash. I don't know where the water-jacket sensor and the outside temp sensor are located. (Not the same as the coolant temp gauge sensor or the outside temp digital readout sensor in the instrument cluster.)

whunter · #15 12-21-2009, 11:18 AM

Blower motor issue fixed.

Roy,

Thanks for explaining the fan fuse issue. I found it and think that was the culprit.
AFTER I doused a full bottle of sewing machine oil into the fan motor bushings. So, the fan runs a bit smoother now.

So, As you can see from the attached photos, the copper cable has about the same resistance as the flimsy (Zinc?) .7 OHMs It will just have to do until I can get to the dealer tomorrow.

My High, Low, and Auto fan (Medium Speed) is back.

Now the only question I have is:
What kind of James Bond-ish gadget would Q install in this car?

Any ideas?

Thank you!
Michael_Vila