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1959 220S cabriolet, 1983 240D original owner, 1999 E300 turbo diesel, 1988 560SL, 2003 SLK320
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Discussion Starter #1
The recent thread on climate control codes got me to check mine. I don't ever recall doing it in the winter. #1 and #2, inside and outside temps are correct. #3 and #4 come in at about 100° and #5 comes in at about 40°. I think I need a little refrigerant because my AC is a little weak. My heater seems to be working reasonably well. So my question is, are the readings I'm getting appropriate for winter driving, i.e. outside temps in the mid-30's and the automatic climate control set to 70°?
 

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2007 E320 Bluetec, 2008 320ML CDI
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2,495 Posts
Going from memory as I didn't drive the car today:
1 - 73°
2 - 30°
3 - 104°
4 - 104°
5 - 45°
6 - 182°
7 - 1

This with the temp set at auto 69° (both sides) and the car warmed up from a 20 mile drive.

My HVAC seems to report a higher value for #1 than what the temperature is set at. Might be that OLD thing at play.

Skippy
 

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1999 E300 TD
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2,045 Posts
The good news is that the in-car temp sensor is reporting 73.

The other good news is that you have set your control to 69.

The question is which is correct-----do you have a small thermometer that you can suspend from the over head control to get a third reading.

Alternatively, see if the variance moves, move the control to 73, let it go through a cycle and retest the in car temp.
 

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E320/E250 Bluetec Ford F350 6.7l
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36,732 Posts
You have to consider some tolerances. First temperature sensors are not very accurate per the design. I have 3 thermometers inside my living room and each will show different temperature. Than it is common that some moisture on the sensor will fool it pretty bad. I have it with outside sensor all the time while leaving the car wash. Than the cabin thermometer is located at the ceiling, while clima controllers are under the dash. Can you imagine different readings?
The sensors in my car can be way off for some reason. I have to set them to 75F to avoid frozen elbows. The same with heating. Than other time they come back to normal. I am not splitting hair over it. Just push the button to adjust.
Now refrigerant pressure at 1 is low. You might want to fix it for winter defrosting.
 

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1999 E300 TD
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You have to consider some tolerances. First temperature sensors are not very accurate per the design. I have 3 thermometers inside my living room and each will show different temperature. Than it is common that some moisture on the sensor will fool it pretty bad. I have it with outside sensor all the time while leaving the car wash. Than the cabin thermometer is located at the ceiling, while clima controllers are under the dash. Can you imagine different readings?
The sensors in my car can be way off for some reason. I have to set them to 75F to avoid frozen elbows. The same with heating. Than other time they come back to normal. I am not splitting hair over it. Just push the button to adjust.
Now refrigerant pressure at 1 is low. You might want to fix it for winter defrosting.
It's Christmas, I am going to pass on this most outrageous statement
 

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2007 E320 Bluetec, 2008 320ML CDI
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Plutoe,

I was offering my temps to the OP.

Today I drove and paid slightly better attention:
Interior set at 70°, Auto - both sides. Car warmed up from a 20 mile ride.
1 - 71°
2 - 33°
3 - 104°
4 - 105°
5 - 44°
6 - 182°
7 - 2

Kajtek1,

The A/C has a leak in the evaporator and I'm planning on replacing that before summer, so I'm not planning on adding more R134a until then.
Around here heat is usually sufficient to clear the windows. It would be nice to have the dehumidifying effect the A/C brings, but............

Skippy
 

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1959 220S cabriolet, 1983 240D original owner, 1999 E300 turbo diesel, 1988 560SL, 2003 SLK320
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Discussion Starter #7
Thanks Skippy. Either both of our cars are functioning properly or they are both bad. :) Our numbers are very similar. What I didn't report was my #7 which was also 1 and my #6 which was 160°. That coolant temp is another thing I wanted to ask others about. In the summer mine goes up to about 170°, but in the winter it is only 160° or so. I think that's a little low. I've been carrying around a new thermostat in my trunk for a couple of years. I'm due for a coolant flush this spring, so maybe it's time to change the thermostat too. Anyone else got some winter temp numbers for me to compare?
 

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E320/E250 Bluetec Ford F350 6.7l
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The engines temperatures should be in the range of 80C or 180F. It changes only +- 3C between different models. Usually thermostat start opening at 75C and fully opens above 80C.
Don't replace the thermostat unless you confirm it bad with infra red thermometer.
 

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1959 220S cabriolet, 1983 240D original owner, 1999 E300 turbo diesel, 1988 560SL, 2003 SLK320
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Discussion Starter #9
I tried to check the EPC to see if the sensor for the climate control and the cluster gauge were the same - couldn't find the answer. Assuming there are two different sensors for them and both the gauge and the climate control diagnostic are reading 160°, isn't that proof enough that it might be thermostat time? Anyone know if there are two different sensors?
 

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2007 E320 Bluetec, 2008 320ML CDI
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Sokoloff,
An old school method of temperature checking I use is to lightly grasp the upper radiator hose (engine running at normal operating temperature). If it's 180 degrees it will be too hot to hold for more than a second or so. 160 degrees more easily touched.
Unscientific as all heck, but if you don't have a temp probe it might provide a clue. If you have access to a car you know to be operating correctly then you'll have a comparison.
My guess is that your thermostat has seen better days and fortunately I think they fail in the open position.
Given your geographic location 160 degrees probably gets things warm enough except for the mid-30's stuff.
I suspect there are different sensors for the HVAC and the dash. My dash gauge shows 1 wand width above 80 which relates to to my 182 degree reading from the HVAC.
YMMV
Happy Holidays
Skippy
 

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E320/E250 Bluetec Ford F350 6.7l
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I tried to check the EPC to see if the sensor for the climate control and the cluster gauge were the same - couldn't find the answer. Assuming there are two different sensors for them and both the gauge and the climate control diagnostic are reading 160°, isn't that proof enough that it might be thermostat time? Anyone know if there are two different sensors?
Not really. Besides the tolerances I was mentioning before you do have external temperature factor.
The 180F rated thermostat start opening at around 160F. When with 70F outside it will take full opening to keep the engine at 180F, at 15F outside the small opening at 160F might be enough to keep the engine at this temperature.
 

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1959 220S cabriolet, 1983 240D original owner, 1999 E300 turbo diesel, 1988 560SL, 2003 SLK320
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Discussion Starter #12
Well, we've got Skippy in Michigan and my son in Boston both showing about 182°. Yours in SF might not be quite the same as ours, but I'd be curious to know what it reads. BTW my mpg is down a couple of notches too. I'm thinking that could be related.
 

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1959 220S cabriolet, 1983 240D original owner, 1999 E300 turbo diesel, 1988 560SL, 2003 SLK320
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3,513 Posts
Discussion Starter #13
Just to wrap this up at least as far as my question goes, I decided to change the coolant a couple of months before I planned to and also do the thermostat. With the new thermostat it now runs about 10° higher than it did before, right around 172°. So I feel a little better about the running temp now.
 
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