'92 300E....does anyone know how to test the outside temperature sensor? - PeachParts Mercedes-Benz Forum

dablk1 · #1 12-06-2010, 09:13 AM

I am referring to the sensor for climate control...not for digital display.

Cal Learner · #2 12-06-2010, 09:19 AM

Does the climate control monitor outside temperature? I never knew that. Thought it only sampled inside temperature. Where is this outside temp sensor located?

dablk1 · #3 12-06-2010, 09:34 AM

It located on the blower motor housing below the wiped motor.

dablk1 · #4 12-06-2010, 09:43 AM

It's sort of shaped like a "J", 2-3" long and it plugs in behind the glovebox. I am not referring to the aspirator motor. If you tink about it, how can the CCU monitor inside temp without knowing outside temp.

mespe · #5 12-06-2010, 11:15 AM

measure resitance, should change with temperature, not sure which direction,,,

Cal Learner · #6 12-06-2010, 11:17 AM

I'm missing something here. How does a sensor mounted behind the glovebox measure outside temperature?

dablk1 · #7 12-06-2010, 11:19 AM

It's not mounted behind the glovebox. That's where it's plugged in. It's mounted on top of the blower motor housing below the wiper motor.

dablk1 · #8 12-06-2010, 11:19 AM

It's not the sampler motor.

dablk1 · #9 12-06-2010, 11:22 AM

Here it is Cal
http://w124-zone.com/downloads/MB%20CD/W124/w124CD1/Program/Climate/83-547.pdf
I found this after doing some research.

Cal Learner · #10 12-07-2010, 09:00 AM

Sure enough. After 23 years of owning my 124 and studying its systems thoroughly, I learned something new today. Looks like an easy diagnostic test for it too. Still trying to figure out why the CCU needs to monitor outside temp in order to keep inside temp at a set level. Anyway, thanks for the info.

dablk1 · #11 12-07-2010, 09:29 AM

I'm not quite sure how it work either, but mine is faulty. I was having the weirdest thing happening. When I started out in the morning and turned on the heat it would work fine then start blowing cool air from the vents once it reached selected cabin temp. The flap would stay closed and the fan speed wouldn't change. When I rolled the windows down to let some cold air in the vents would start blowing warm air again. It seemed as though the CC wasn't reading the outside temperature. I unplugged B10/5 and it started working perfectly.

JohnS · #12 12-07-2010, 10:08 AM

Those are typically negative temperature coefficient devices, so resistance should decrease with increasing temperature. You should be able to get it to change resistance by holding it with your fingers. Typical resistance would be around 5 K ohms and it will move down as you heat it up.

dablk1 · #13 12-07-2010, 10:22 AM

Well according to the testing chart....you would be right. Temp up/resistance down

ps2cho · #14 12-07-2010, 02:18 PM

The outside temp sensor works with the fresh air front flap. When the outside temperature exceeds inside temperatures, it closes and vise versa depending on how you have the temperature dial set.

A good check if the pod is broken is to drive on the freeway and feel if there is air coming through the vents with the CCU set of OFF. When OFF, there should be no air coming through. I know this because I replaced my pods on my 260E and it does not blow any air through....my 300TE OTOH does and it is quite irritating on a cold day because then you have to close the vents completely. Also it does not help when it is hot outside since it is not closing.

dablk1 · #15 12-07-2010, 03:16 PM

Well I have the visa/versa issue. It was open and should have been closed. I was watching the flap when I disconnected/reconnected while I had the glovebox out....by the way I don't think that I get any air through the vents when climate control is off.