Something wrong with the climate control in my SLD- same temp outside as inside - PeachParts Mercedes-Benz Forum

ROLLGUY · #1 07-16-2023, 08:32 PM

Enough said

Mark123 · #2 07-16-2023, 10:39 PM

Yeah, It took me a minute.

Benzadream · #3 07-18-2023, 11:42 AM

38° F. is an amazing discharge temperature! Very impressive! Kudos.
Just out of curiosity, what was the relative humidity that day?
Also wondered when you last calibrated your analog thermometer, if ever?

ROLLGUY · #4 07-18-2023, 06:59 PM

Quote:

Originally Posted by Benzadream

38° F. is an amazing discharge temperature! Very impressive! Kudos.
Just out of curiosity, what was the relative humidity that day?
Also wondered when you last calibrated your analog thermometer, if ever?

It was actually pretty dry driving through the desert. Although I believe both thermometers are accurate, neither has been calibrated.

Shern · #5 07-18-2023, 05:22 PM

I’d like to know at what speed this was taken.

ROLLGUY · #6 07-18-2023, 07:02 PM

Quote:

Originally Posted by Shern

I’d like to know at what speed this was taken.

Both thermometers registered those temps for about 40 minutes while driving hwy 138. Much of it was 55mph, with some slow down and stopping at lights. The fan was on high with the soft top and windows up....Rich

Benzadream · #7 07-18-2023, 08:10 PM

I have no idea how you'd check calibration of the dash mounted thermometer. However, the other one, inserted into the vent, is very easy to check and calibrate.
Take a small glass or cup, deep enough to submerge the thermometer probe, pack it with crushed ice to the top and add cold water. Submerge your dial thermo probe almost up to the gauge and let it sit for a minute or two. The slurry will be 32 degrees F. so, after a short while, that's what the dial should read. If it's not reading 32, look at the back of the dial and there should be a nut, with flats, between the dial and the probe. While holding the nut stationary, and the probe still submerged, simply turn the dial, in whatever direction is needed, to make it read 32 degrees F. on the nose. All done! Your thermometer is now calibrated and reading accurately as verified by the 32 degree water/slush. If nothing else, I always like to see how close mine are to being accurate at 32 degrees. They have a tendency to creep over time or with accidental shock and rough handling.

ROLLGUY · #8 07-18-2023, 08:57 PM

Quote:

Originally Posted by Benzadream

I have no idea how you'd check calibration of the dash mounted thermometer. However, the other one, inserted into the vent, is very easy to check and calibrate.
Take a small glass or cup, deep enough to submerge the thermometer probe, pack it with crushed ice to the top and add cold water. Submerge your dial thermo probe almost up to the gauge and let it sit for a minute or two. The slurry will be 32 degrees F. so, after a short while, that's what the dial should read. If it's not reading 32, look at the back of the dial and there should be a nut, with flats, between the dial and the probe. While holding the nut stationary, and the probe still submerged, simply turn the dial, in whatever direction is needed, to make it read 32 degrees F. on the nose. All done! Your thermometer is now calibrated and reading accurately as verified by the 32 degree water/slush. If nothing else, I always like to see how close mine are to being accurate at 32 degrees. They have a tendency to creep over time or with accidental shock and rough handling.

I have no doubt that the factory thermometer is accurate considering the "German Engineering"

. As far as the dash vent thermometer, I believe that is accurate as well. I am running R12, Sanden 7 cyl compressor, a parallel flow condenser, and side by side MB condenser fans. I was very comfortable in the cab, and sometimes even a little cold. However, it might be fun to check the thermometer just to be sure. The process sounds easy enough, thanks.

Benzadream · #9 07-19-2023, 09:00 AM

No problem. R12 is still the best, hands down! Your utilization of it explains a lot! After posting I figured you probably had " all your ducks in a row". Hopefully other users will benefit from the calibration info as many of us have those small dial thermometers.
You're correct, it is fun to check the calibration and determine the accuracy. Even a small error of 3 or 4 degrees can mean a lot. Edit: The "cheapie" dial thermometers wont have the calibration feature/capability....

Shern · #10 07-20-2023, 04:10 AM

Rich, which expansion valve are you running?

ROLLGUY · #11 07-20-2023, 09:23 AM

Quote:

Originally Posted by Shern

Rich, which expansion valve are you running?

Factory original. I would have pretty much had to remove the dash in order to replace it. Even getting the adapter fitting I made installed was a bear.

Shern · #12 07-20-2023, 10:04 AM

Something I’ve wondered about for a while…

Mine was swapped out for the 134 valve by the PO and I’ve been thinking about the impact it’s been having on my system ever since.

Benzadream · #13 07-20-2023, 08:32 PM

Here's my '83 240D discharge temp a few days ago. Ambient was 85 degrees with humidity approx. 90%. I was driving on secondary roads (traffic, stop lights, 40-45 mph). The system was converted to R134a by the PO. Don't know if the expansion valve was changed or when the filter/dryer might have been replaced (if ever). The compressor is the original R4.
Not quite "ROLLGUY's" 38 degrees, but pretty good for a 40 year old R4 system. It keeps me comfortable in those temps.... The car has 220K on the odometer.

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