W210Wagon

All of the displays on my car are set to fahrenheit. I was trying to trouble shoot my A/C system. When I press and hold the "Rest" button on the climate control, I get a 1 and another number which is supposed to be the temperature of the interior of the car. Is that temp display in C or F? Thanks.

raymond g-

i dont think we're able to give you a response with certainty with the minimal
info you've provided about your car. but if you post the remaining diagnostic
data, we could probably make an educated guess. seat of pants would suggest ºF

RichardM98

Instrument cluster is programmable and independent of the CCU. CCU is metric -- Celcius (temp) and bar (pressure).

W210Wagon

Thanks Richard.

Plutoe

Just to remove a potential cloud, if your AC control unit is coded to C the self test applicable results will be in C/metric and conversley if coded to F the self test results will be in F/English or US English------dosent that seem logical to you??

Plutoe

Just to remove a potential cloud, if your AC control unit is coded to C the self test applicable results will be in C/metric and conversely if coded to F the self test results will be in F/English or US English------dosent that still seem logical to you??

A very simple test is to set a temp for R or L side----what numbers appear 10 and 20's or 70 and 80's---the bigger numbers are F.

Exception: actual value test for 7 will be in metric(bar)

W210Wagon

Plutoe, as I said in the original post everything on the dash displays in F. The dash read out for the exterior temperature is F. The climate control is in F. So are you saying that the interior temperature ("Rest" for >5sec) is also in F?

Plutoe

Ahhhhhhhhhhhhhhhhhhhhhhhhhhhh yes!

Don't forget to do the fault test first----then clear the faults---then do the test again and write down the faults if any-----then do the actual value test(the test we have used way more bandwidth that we should have)---then post the data.

PS Make sure the car is running and up to temp before the actual value test is applied!!

raymond g-

my USA marketed E320 definitely reads ºF maybe I have a collectable vehicle

RichardM98

Mine is a 98 like the OP's. Maybe it was changed in 99 or maybe it can be switched via SDS like the cluster which would explain everyone's comments.

raymond g-

prolly. that's kind of why i asked for the OP to post the rest of the figures from the
diagnostic test...afterwhich the answer would be obvious as it depends on the setting

Plutoe

I believe the changes occured in 1995/96----if you have code 581a, thats the new one(AAC-Automatic Air Conditioning) the older one is (Tempromat---dial type)

W210Wagon

I finally had a chance to run all the diagnostics on the climate control unit.

First I checked for trouble codes. It listed 3 codes. 231 (ECT sensor), 234 (Sun sensor) and 235 (Emissions sensor). I cleared the codes and drove it for a day. Then I checked climate control displays. The dash displayed 93F external temp, the engine coolant temp gauge showed about 85-90C and the climate control was set to 72F on the right and left sides and they were on "Auto". I got the following readouts:
1 36
2 40
3 36
4 33
5 64
6 91
7 09
8 47
9 04
10 2.0
11 4.0
13 3.6
20 0.0
21 06
22 00
23 00
24 13.3
40 71
41 34
42 72
43 152

After that I checked to see if any DTC's had showed up and there were no trouble codes displayed.

I also checked to make sure the interior temp sensor fan was working and I put a small piece of paper over the intake side of the sensor vent and it stayed in place. So that seems to be working.

So this is what my car is doing. If it is cool outside (mid-high 70's) the A/C works almost normally. Cold air out of both sides but there is considerably more volume and obviously much cooler air out of the right side. I made a short trip the other day. When I started the trip it was in the high 70's outside. When I arrived at my destination, the outside temps were in the mid-high 80's. The A/C worked the whole time. Under normal conditions when I start the car and it is that warm (mid-high 80's) outside, I get barely cool air out of the LH vents and a relatively low air volume. I get nice cold air out of the RH vents with normal air volume. Within a few seconds, the air on the LH side gets warm. The air stays cool on the RH vents for about 4 minutes and then gets warm. Help. Please.

Plutoe

Very nice job!

The guidance actual values for your data are 5(evap temp sensor),7refrigerant pressure sensor) and 8(refrigerant temp sensor)

5 way to high should be in the low 40's
7 way to low should be at least 14 at idle
8 way to low--should be in proportion to number 7

If you EC lamp is off, the lack of cooling is then typically low refrigerant level

If you EC lamp is off and the system is full then your compressor can't make pressure.

The big question is then ---how do I know the quantity of refrigerant in my system---you go to and AC shop and they have a set of gages that will tell them instantly!!

W210Wagon

Thanks Plutoe. I'll check that. I have a friend who specializes in Porsche repair and he has the complete recovery system. Would low freon explain the large difference of air volume and temperature between the right and left sides? Or is that another issue that I need to address?

Plutoe

No, I believe that because the low pressure causes 5 to be so high that there is much reduced cooling at the evaporator yet large volumes of much warmer air wanting to get cold that not all air is the same temp.

I bet that if you reduced the fan speed considerably, that phenomenon with less air would equalize and one would see colder air from all vents(reduced evap temp is cooling much less volumes and velocities that all vents would be simular in temp. Thats a guess I was not a physics major!!

renault12ts

If, on my car, I change the display in the instrument cluster from C to F...the temp in the CCU also changes from C to F. So, all displays should be the same scale.

Plutoe

That is interesting and assuming you really do live in England, a non metric country, but yet you have indicated they(MB) coded your IC and AAC to metric. Is that what you are trying to convey

Remember the IC is coded seperatly to the ACC.

I guess if you wanted you could have metric on one and non metric or English on the other. That would be interesting especially regarding your spedo

renault12ts

The UK is metric (except for speed and distance ), I don't live in England though...but another of the UK countries.

Anyway, there is no choice. I can change the display on the instrument cluster to F or C. The CCU follows what is set on the instrument cluster and cannot be set independently.

Also, when the IC is set to F or C, the diagnostic values will also be in the same value as set on the IC.

Remember...my car is a facelift.

My speedo is in MPH (with a second scale inside showing kph). I have a digital display in the IC which can display MPH or KPH as I see fit.

W210Wagon

Well Plutoe, you were right on the money. I took my MB to my friends shop where we recovered 1.10 pounds of R134 from the system. We vacuumed the system for about a half-hour and installed a hair over 2 pounds (950 grams) of R134. When we started the car initially, I still noticed obviously colder air out of the RH vents. Checking with a laser temp gauge showed about a 7 to 8 degree difference. However, when the system finally got cool it reached the same temperature on both sides. Actually it is cooling better now than when it was serviced after an evaporator replacement, 2 years ago. It might not have had a full charge at that time. But I am still concerned about possibly loosing freon. I used a sniffer to try to find a leak but didn't detect anything.

Thanks for the help. Having a working A/C was really nice today since the temps were in the high 90's. Whew....

RichM

If you would, run the actual value test again and post the numbers. I am trying to understand the ratios of 5,7 and 8 from a non functioning system to a functioning one. I know what the numbers should be once the system is functioning, but not from a non functional to a functional system. Thanks.