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1995 E300 Diesel, 1994 S350 TurboDiesel, 1992 Ford F250 7.3L IDI Diesel, 1996 MotoGuzzi Sport 1100
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Discussion Starter #1
My daily driver 1995 E300 Diesel recently stopped blowing air cold/hot. Here are the symptoms and what I've done so far to diagnose/isolate the problem:

  • 1995 W124 with OM606.910 diesel engine - 132,000 1 owner miles. Dealer maintained (for what that matters) by previous owner.
  • Car starts, idles and runs fine - A/C/Heater blower and recirc blower don't blow. The rest of the climate control seems to work. Dash lights are fine, Climate control lights don't work.
  • It did this a few times (stopped blowing) and then worked again, but has finally stopped working at all times. Nothing happens when either of the fan switches are pushed nor when temp dial is changed... cold, hot, etc.. nothing.
  • SRS Light comes on shortly after starting engine and driving with A/C Climate control on - I noticed this the first couple of times the blower stopped working. Next time car started the blower worked until recently. SRS warning light does not come on when climate controls are off.
  • ABS light also sometimes comes on after a few minutes if Climate controls are turned on (blower switch - auto and both A/C and temp must be in position and compressor going). ABS warning does not come on when climate controls are off. SRS and ABS are related (symptom) to blower motor issue it seems.
  • Checked ignition switch and steering wheel airbag to see if they had any effect on SRS light - none.
  • Compressor comes on and A/C lines get cold fast - when switched to external air and driving on hwy, cold air comes in for a while.
  • I can hear the flaps opening and closing when switching between A/C modes. Fresh air does come in when proper switch is pushed.
  • I'm assuming blower is still good because each time it resumed working it ran just fine and the 30 A fusible link (or is it 15A?) to the blower is still OK.
  • Hissing comes out of A/C vents when A/C is on for a couple of minutes after start (I turn it off quickly so as not to damage climate control)
  • Auxilliary fans in front of radiator do not come on at all
  • I have removed and tested the OVP relay - it shows 0.51v when tested in diode mode - no rattles. I'm assuming it is good, though I may replace it as a precaution. I have not opened it up and checked solders yet.
  • Red light on recirculation fan switch comes on but recirculation fan does not blow either. I'm guessing that a whole circuit with both fans is turned off because of a over or under-voltage or current condition but if it isn't OVP then what is it?
  • When I drive on the Highway without the climate control engaged the SRS and ABS lights do not come on at all and when tested in a parking lot the ABS works quite well (no, I haven't tested the airbags for SRS and don't intend to do so).
  • Checked 8A white fuse #3 for CCU in fusebox - it is good
  • Tested the 30A blower fuse - disassembed - it is fine (in one peice no cracks)
  • Checked battery voltage - 12.6v steady with ignition off
  • Checked alternator voltage - ~13.88v with car idling or light throttle up to 14.2v - doesn't look like it needs alt. voltage regulator yet.
  • Serpentine belt is in good shape and adjuested to proper tightenss
  • Dash lights are working when turned on and rheostat works fine.
  • Next Step: I'm going to likely check/test the fan independently (and replace the motor if need be - replacement fan is about $90 - or $6 for brushes) to eliminate that possibility.
  • Thought 1: it could be one of the temp sensors going out, but there seem to be about six temp sensors and I'm not sure where to start or how to test them properly.
  • Thought 2: It seems likely to be the CCU, but I'd like to eliminate all the other more common and less expensive options so any feedback is welcome.
  • I'll probably test some more variations of having the Climate control on - does SRS and ABS only come on when cold/compressor are engaged or does it happen with heat and blower turned on? Noticed SRS comes on when compressor engages, but goes off when climate control turned off
  • I have acquired the workshop manual and schematics and am beginning to trace the issue down, but that is a big task.
These are my next tests:
  • Climate relays - test. I think they are behind the fuse box, but I have to find out which ones for sure.
  • CCU - A/C/Heater controller in center console (trace voltages)
  • blower motor test
  • blower motor regulator replacement (I believe it is under the blower?)
  • Possible temp switch on the drier? or maybe other temp sensors?
  • I'm thinking of spending the $100 to replace the OVP and voltage regulator anyway - last and just in case, but it seems precautionary. Any thoughts?
I hope this is enough good info for those of you inclined or experienced enough to help with the diagnosis. If there is something else you want to ask, just let me know.

It sure seems like a voltage condition because of the intermittent nature at first and also the fact that SRS and ABS lights only come on when the climate control is turned on. Any hints, ideals or experiences that might bear on this would be greatly appreciated. I've already taken a bunch of pics to document the process of finding the OVP relay and testing it and will fully document the whole troubleshooting and testing process of getting the A/C blower working again (I'm currently an unemployed technical trainer and computer consultant so documentation for knowledge bases is what I do).

Thanks in advance for whatever informed feedback or info you can give me.
 

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Any luck solving this?

John,
I have a 95 E300 Diesel that has started doing the exact same thing. I am also in Austin, so you know how miserable it would be to not have A/C going into the summer. Any luck solving this?
Thanks,
John
 

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1995 E300 Diesel, 1994 S350 TurboDiesel, 1992 Ford F250 7.3L IDI Diesel, 1996 MotoGuzzi Sport 1100
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Discussion Starter #3
Yes, it was the blower. I replaced it and the whole system works great now. I did find replacement brushes online for the fan motor, but I was too lazy to replace them and see if I could make the original fan motor work again. I just bought a new one and put it in and had A/C again and it was worth it. Good luck I hope yours is as simple as that.

JR
 

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W124
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The first time you change the blower it might take you a couple of hours. Its mounted on the cowl under the windshield wiper motor. Its a pretty straightforward job but it takes time and patience to remove some of the trim parts that are involved.
 

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86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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Thanks for the reply. I have heard the fan is a bear to replace. Does the dash have to come out?
No, the dash isn't part of the R/R for the blower motor. If you have resonable DIY skills, this will take you about 3 hrs to do. If you ever have to do the job a second time, it will take you about 45 min.

http://www.peachparts.com/Wikka/W124BlowerMotor

Good Luck,

Jayare
 

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1995 E300D, 1998 E300TD
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122 Posts
I also have a 95' E300d. 168K ( intermittent cabin blower )
The blower fan wound work intermittently. Bumps and general driving would turn it on and off. I also figured it was the Blower motor going bad so I decided to gain access to it. ( and also replace the cabin filters)
found the blower not working, I moved the wire harness around and the fan came on all of the sudden. I traced the problem to an unsoldered pin at the three prong connector to the frame. I disassembled the connector. ( easy clam shell design) and re soldered the (yellow ) wire to the pin connector. Reassembled and the fan works great now! Just in time for summer.
 

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1999 ML 320; 1995 E300 Diesel
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This thread has been very helpful in removing the blower motor in my 1995 e300 diesel -- twice. This time I want to replace the blower motor resistor and am having trouble getting it out. Any helpful diagrams on this?
 

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Current, 90 300CE,95 E320, 92 400E, Sold 70 250C, 91 190 2.6, 91 420 SEL, 95 300D, 87 TD
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1,529 Posts
sorry off-topic

I also have a 95' E300d. 168K ( intermittent cabin blower )
The blower fan wound work intermittently. Bumps and general driving would turn it on and off. I also figured it was the Blower motor going bad so I decided to gain access to it. ( and also replace the cabin filters)
found the blower not working, I moved the wire harness around and the fan came on all of the sudden. I traced the problem to an unsoldered pin at the three prong connector to the frame. I disassembled the connector. ( easy clam shell design) and re soldered the (yellow ) wire to the pin connector. Reassembled and the fan works great now! Just in time for summer.
I like your picture near your name ME109 Daimler engine. That was a cool upside down v12 better for oil starvation during turns.:cool:
 

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1995 E320 Sedan
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I know this thread is really old, but I just casually started my car like I always do and took it for a spin. The blower motor suddenly stopped working and the abs and srs lights came on. Checked the 30 amp fuse I recently replaced because it went out, it was fine. Everything works fine with A/C off. Compressor works, just no fan blowing. I think the ccu is fine. It's most likely the blower, is it possible to suddenly go out or does it slowly wear out. Thanks.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Are you sure your alternator is putting out like it is supposed to? Take voltage measurements with engine at temp & idling, both with everything turned off as well as on. Then report back.

Could be a simple case of worn out voltage regulator, since the blower takes a lot of juice. As was said in the movie Apollo13, "it's all about the Amps"
 

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^^^Good advice from SBaert. The Mercedes engineers seemed to be playing a cruel joke on us owners because the "not charging" warning light usually will not go on when the regulator fails. A lot of the other warning lights do however as the battery slowly looses potency and the systems start running on insufficient voltage.

Once you rule out the regulator/operating voltage as the cause, check to see that your ignition switch is working properly. When its in the "run" position, jiggle the key back and forth to see if the symptoms change.
 

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1995 E320 Sedan
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Are you sure your alternator is putting out like it is supposed to? Take voltage measurements with engine at temp & idling, both with everything turned off as well as on. Then report back.

Could be a simple case of worn out voltage regulator, since the blower takes a lot of juice. As was said in the movie Apollo13, "it's all about the Amps"
My alternator is a refurbished 143 amp upgrade and I tested it multiple times and get
Idle with no load: 14.38 volts
Idle with the ac, headlights, lights, sub woofer, radio, doors open:14.16 volts
No air coming out of vents and abs and srs light turn on.
Everything works except my blower motor
I think my ignition is fine a/c doesn't work when key is turned to on, or when engine is on.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Refurbished, by who? By Bosch themselves?

ABS and SRS lights coming on is dead giveaway that there is a charging problem. Replace that voltage regulator with a new Bosch unit if in doubt.

The alternator and starter refurb business is many times nothing more than a spit polish job.
 

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1995 E320 Sedan
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Refurbished, by who? By Bosch themselves?

ABS and SRS lights coming on is dead giveaway that there is a charging problem. Replace that voltage regulator with a new Bosch unit if in doubt.

The alternator and starter refurbish business is many times nothing more than a spit polish job.
Yesterday the abs and srs lights came ONLY when the A/C is on. If I have my two amplifiers, headlights on, two electric fans on engine spinning when the car was at 100C, the abs and srs light didn't come on.
Update
Today when I try to turn the A/C on the srs and abs lights aren't turning on and still no blowing through the vents no matter what I click on the A/C, I have a voltage of 13.9~14 at idle with full load.
 

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Also when it worked like a day ago, it worked perfectly, blowed such cold air, and randomly just goes out.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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Replace that strip fuse first and foremost. Many times that is all that is needed. Easy $1 DIY project.
 

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1995 E320 Sedan
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Replace that strip fuse first and foremost. Many times that is all that is needed. Easy $1 DIY project.
The 30 amp fuse was cracked like exactly a month ago, had almost Identical symptoms except no srs and abs light at all, replaced that with brand new 30 amp flosser fuse and worked perfectly until now.
 

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There is a pretty high chance it is the blower motor right, I am looking for some what are the best replacement companies for blower motors, I have found behr-hella and uro, I know uro is an awful company.
 

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'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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It could just be the blower's regulator. There's many threads on testing the blower itself with the three prong plug that feeds it.

Replacing that blower fan with anything other than Bosch is a fool's errand. They're around a $100 if you can get your old squirrel cage off and refit onto the new motor. I wrote a thread on that, but no pics.

Given the fact that your motor has possibly failed, now is the opportune time to replace the motor AND regulator. I serviced my motor, only to have my reg fail like six months later. That's a very frequent scenario too with these cars.

Kevin
 
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