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  #1  
Old 09-05-2003, 02:28 AM
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w124 - Cabin heat goes on and off?

The summer is just about over and it's a bit cold in the morning now. So i use the cabin heating system.

It heats up nicely and temp. adjusts accordingly to the temp. control wheels.
But after about hour the heat shuts completely off..!? It's not just adjusting the temp. -It shuts off!

So i turn the temp. controls to "max" and nothing happens for 10-15 minutes. -And all of a sudden i see the inside of my windscreen gets a little fogged for a few seconds and the heat blasts out in the cabin again..?

This has been going on for 3 days in a row now. What is happening?

Freestyler
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'86 300E optically converted to '95 E300 (Sold)
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  #2  
Old 09-05-2003, 06:40 AM
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Location: York UK
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I'm not familiar with your model but it might be helpful to eliminate the solenoids that control the water flow. On my W124 230CE the heater is full on when the fuse blows since the solenoids must be energised to close off the flow. Someone once said this is designed to prevent passengers freezing to death due to a blown fuse.

Good luck

John
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  #3  
Old 09-05-2003, 11:54 AM
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When you say the heat 'shuts off', do you mean the blower fan cuts out, or that the air gets cold?
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  #4  
Old 09-05-2003, 04:21 PM
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csnow Blower fans are working fine. But the air is cold.

JohnUK Solenoids controlling waterflow!? Is that how it's working?
I thought there was a heater core and it was the airflow through or past this, that controlled the cabin temp.. (all my other cars has had that)

So if i cut the power to the solenoids, the heat should be on full all the time, right?
Were would i find these?

Freestyler
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Never criticize someone until you've walked a mile in his shoes. That way, when you do, you're a mile away -and you have his shoes!


'86 300E optically converted to '95 E300 (Sold)
-Blauschwarz on silver
-Black leather
-17" AMG & 15" AMG for winter
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  #5  
Old 09-05-2003, 04:36 PM
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Not sure about your model but I suspect the solenoids (if they exist) are near the heater matrix under the dash. Someone else will kindly confirm it. I would just find the fuse in the fusebox and remove it to see what happens. If the heat is full on (when the dials are set to cold) then that just confirms they are de-energised and this is normal.

BTW, I assume you do not have air-conditioning.
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  #6  
Old 09-05-2003, 04:46 PM
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This model (at least in the USA version) has an electric control valve. Many cars with simpler 'climate control systems' have a manual cable actuated valve for this.
It is located on the right (passenger side- at least in the US! What side do you drive on?), under the hood, near the firewall. Just follow the heater hoses.

If you cut the power (pull the plug attached to valve pictured below) to the electric valve (sometimes called a "mono-valve"), the default position is wide open, meaning Hot.
I have tested this.
It will still let a lot of hot air through the drefrost vents, even if the system is completely off in this mode.

I suppose it is possible that the valve is 'mechanically' stuck closed, in which case disconnecting the power will not help.
I saw a repair kit marketed somewhere.
Someone here will know.
A new one is like $80 or so.

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Last edited by csnow; 09-05-2003 at 05:04 PM.
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  #7  
Old 09-05-2003, 04:56 PM
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Other items to also check are-

-Inlet for your temperature sensor inlet, located on your car I believe by the interior light/ sunroof controls. Use a vacuum and suck out the dust.

-The above pulls air down the right-side A pillar via a little fan motor located to the right, I believe of your glove box. Check to make sure it is running, not clogged and the tubing going to it is intact.

Keep us posted,

Haasman
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  #8  
Old 12-19-2003, 07:28 AM
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I woke up this semi-old thread because the problem is still ocurring and now it's freezing outside -and inside too. And when it's not freezing, my Benz is trying to cook me alive, blasting full heat..

I would like to check the little fan motor located behind/beside the clove box. but how the heck do i get the glove box out!?

I have removed the screws holding the box, but it still won't come loose.
What am i missing?

Freestyler
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Never criticize someone until you've walked a mile in his shoes. That way, when you do, you're a mile away -and you have his shoes!


'86 300E optically converted to '95 E300 (Sold)
-Blauschwarz on silver
-Black leather
-17" AMG & 15" AMG for winter
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  #9  
Old 12-19-2003, 04:31 PM
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I vote monovalve.
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  #10  
Old 12-19-2003, 04:58 PM
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There are little plastic pegs in the box you pop out with a screwdriver or something (i think, i got a 300CE) unless thats what you got out already. Just wedge it out.
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  #11  
Old 12-29-2003, 02:05 AM
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Problem found.

It was indeed the little fan motor that had given up.
Took it apart and it is definately worn out.
I'll go shopping for a new one.

Freestyler
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Never criticize someone until you've walked a mile in his shoes. That way, when you do, you're a mile away -and you have his shoes!


'86 300E optically converted to '95 E300 (Sold)
-Blauschwarz on silver
-Black leather
-17" AMG & 15" AMG for winter
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  #12  
Old 12-29-2003, 02:08 AM
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My 1998 Ford Taurus LX did this and it was just low on engine coolant. My aunts 2001 Nissan Altima SE sedan did the same thing and it was also low on coolant. I thought that was quite strange for a 2001 car, with 28K miles.
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  #13  
Old 12-29-2003, 12:46 PM
greggyc
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Lightbulb heater cuts off

My 190E 2.6 is doing the exact same thing!!!!! I'll get out there this week and check out the little fan behind the vent/glove box. I can hear something click in that vicinity...but my EVERYTHING cuts off...fan, heat, all of it, and cold air just flows through the vents at 75mph.
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