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  #1  
Old 06-12-2012, 11:36 PM
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Join Date: Jun 2012
Posts: 3
2000 C230 Climate control issue, always cold air

Hi, all,

I have a 2000 C230, 11K miles. Several days ago I found out my car can only blow cold air no matter the temp setting is,except I put the climate control dial on defrost. Both drive and passenger side act the same. Which is not a big problem yet since it's summer now.

Since I can still get heat on defrost, the heater cores are probably fine. I did some search and think it could be the duo-valve. I unplug the duo-valve, full heat will come since it will be open by default. I test the voltage on the three pins which operates the valve. On defrost mode, the voltage is 9.24 constant; 13.86V constant on all other temp setting, which I think it should be intermittent depend on the temp setting.

So my questions are:

What is the correct voltage reading on these three pins? Shouldn't I get 0V while setting on defrost and 12V intermittently on other setting?

If the voltage reading is wrong, does it mean whatever controls the valve went wrong?
----------------------------------------------------------------------
Update on June 13:

opened duovalve and cleaned it, everything looks fine and clean.

what do I do next?
--------------------------------------------
Will a bad coolant temperature sensor cause no heat?
Any help would be appreciate.

Last edited by benzcheng; 06-14-2012 at 05:01 PM.
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  #2  
Old 06-13-2012, 08:26 AM
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If you unplug the heater valve, you should get HEAT.

If not, either the heater valve is STUCK or the heater core is plugged.
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  #3  
Old 06-13-2012, 10:25 AM
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Sounds like the opposite problem I had with my son's 2000 C230K. Hot air all the time, no cold air yet the compressor line was ice cold.

New heater valve did the trick. I had a new one put in but apparently they can be cleaned and put back into service.
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Old 06-13-2012, 12:02 PM
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Quote:
Originally Posted by mbdoc View Post
If you unplug the heater valve, you should get HEAT.

If not, either the heater valve is STUCK or the heater core is plugged.
I did unplug it, and the heat came back as it should.
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