mcanix

I have searched many different forums to no avail. About 2 weeks ago, after starting the car and hitting the road, the compressor would cut off after 2-3 minutes and it would start blowing ambient air. The control panel was set to auto and temps to 68 degrees. Freon pressures are good. If I make a quick stop at a store for say 5 minutes, I come out, start it up and the same thing happens. Cold air for 2-3 minutes then ambient. I checked last night and verified that when the compressor disengages, the aux fans also shut down. One last issue is either the blend doors are playing games or the blower is fluctuating since sometimes the airflow changes.

I ran the AIRCO test using CarSoft and the control module checked okay.

There are no codes stored in the control head.

I performed the control head test to look at the various readings and they are as follows-

Test
1. In car temp. sensor 28
2. Outside temp. sensor 29
3. Lt. side heat exchanger temp. sensor 16
4. Rt. side heat exchanger temp. sensor 15
5. Evap temp. sensor 60
6. Coolant temp sensor 86
7. Refrigerant pressure 8-12
8. Refrigerant temp. sensor 34
9. Not assigned 22
10. Blower control voltage 4.5
11. Emission sensor 2.9
12. Sun sensor 4.3
20 Auxiliary fan control current 6.6
21.Engine speed 06
23.Circuit 58d(% of batt. voltage) 00%
24.Battery voltage 13.5
40.Software status 71
41.Software status 34
42. ??? 72
43. ??? 152

Can anyone make heads or tales of this. Thank you for reading this long post and I would greatly appreciate any feedback
Regards,
John

kajtek1

For proper troubleshooting I need 3 readouts of sensors 1-8
1. on cold morning before engine start
2. on hot afternoon entering park car engine off
3>>> 2-3 minutes after #2 with engine on.
From single readout your evaporator temp sensor is shot, but full troubleshooting will tell for sure.

mcanix

Hi Kajtek1,
Your previous posts on these forums have helped me with a number of cars and I thank you!
So just to clarify, you want me to provide the results of the readings of #5, Evap temp. sensor using the conditions stated above?
Regards,
John

kajtek1

Do all 8 sensors.
Even #5 is main suspect at this time, some other things might show up.

mcanix

Hello again,

I ran the tests today as you specified. The results are-
Scenario 1-
Sensor. Result
1. 23
2. 23
3. 21
4. 21
5. 62
6. 23
7. 05
8. 22
Scenario 2-
1. 28
2. 30
3. 30
4. 30
5. 64
6. 89
7. 14
8. 39
Scenario 3-
1. 28
2. 30
3. 26
4. 27
5. 60
6. 85
7. 17
8. 45

Thanks much!

kajtek1

Yeah. Your evaporator sensor is definitely bad, showing 62C on cold morning.
The sensor is easy accessible when you dive head down under the pedals, but lately one member posted that you can gain easy access by pulling the cluster.
Looks like you did #2 short time after engine shut down, not after long parking, but does not affect the #5 judgement.
If you are handy with soldering - a Turkish member found that you can replace faulty resistor for couple of bucks and you don't need DAS for it

fabbrisd1

The China knockoff part is like $13:

mcanix

Kajtek1,

Your awesome! I have no problem replacing it with the OEM part but is DAS necessary to fix it?

kajtek1

read carefully
your refrigerant shows on low side, so redo #2 and 3 readings after you fix the sensor.

mcanix

Gotcha! Sorry about that. Whenever I read something, I am always looking for the prize. Gets me in trouble at work sometimes. I am going out of town this week and will be changing it next Saturday. I'll keep you posted. Thanks again! Do you know much about the w202 HVAC system? My daughter has a 96 that has poor airflow with the blower on high. I've read the sensor values and they all seem normal and no codes were stored in the control unit. I'm thinking blend door problems but I haven't dug into it too much. Lastly, what other non-OEM software/interface do you recommend? I currently have CarSoft.

kajtek1

Can you post a picture of W202 climate controls?
I know lot of MB models share the same systems even if the buttons look different, but 1995/96 was era of going digital, so lot of things changed.
Than on system turning 20 years, the elements that control the flappers are expected to start breaking down.
How is W202 blowing in defrost mode?
I tried to buy advanced computer, but found out too many gimmick.
I have couple of computer-based scanners who can read life data, but even they were cheap at start, to read MB I would have to buy 2 additional discs at about $150 each and manufacturer can't tell if I in fact will read the data I want.
That is why I am seeking methods how to repair those cars without DAS and worse come to worse, I know a technician who owns one, is good with it and comes to me for a case of Polish beer.

fabbrisd1

Evap sensor does not require Star/DAS - it's just a streaming sensor.

mcanix

Please see attached. The defrost airflow is pretty lame. Thanks again for all of your time.

kajtek1

This is single zone climatronic, that should allow troubleshooting just like dual zone on W210.
The picture shows the blower on high with defrost mode, what I assume is working?
If it doesn't change to vent mode, that would indicate vacuum leak in the system.

mcanix

Yes, it was set to defrost with the blower on high but the actual airflow was pretty weak from what I am used to. I'm guessing one or more of the vacuum elements? I did the sensor test and the results are as follows-

01 = In-car temp sensor 91
02 = outside temp sensor 84
03 = left heat exchanger (heater core) temp sensor 82
04 = right heat exchanger sensor (it skipped this step)
05 = evaporator sensor 73
06 = coolant temp 104
07 = refrig. pressure in bar 7.1
08 = refrig temp sensor (23*9 = 23.9deg C) 86 F
09 = nothing
10 = Blower control voltage (great for evaluating blower controller problems) 410
11 = emissions sensor (B31) e.g. 3.1 = 31.v (it skipped this step)
12 = sun sensor 4.2 = 4.2v (it skipped this step)
20 = aux fan control 6.1 = 6.1ma (max 10ma) 0
21 = engine speed 0
22 = vehicle speed 0

fabbrisd1

To be helpful - if "total airflow" is the problem - putting vent/diversion defrost/cabin-air to the side - then the suspect will be the blower regulator.

I am just trying to clarify the circumstance to be of help.

The "amount" of air is a function of the blower - and it is not uncommon for the regulator to give up the ghost.

Is this the C32 ?

Depending on yr/model - the reason I ask - is the DIY replacement for some blowers is different - and on those some best done with aftermarket/parts - on thos models Mercedes later updated both regulator+ blower to different style combo.

Keep the beat !

kajtek1

The sensors readout in defrost mode is not usable, sorry.
Defrost is default mode, so if the flow is weak, than the problem is elsewhere.
I partly agree with fabbrisd that blower regulator is next suspect, but than I would believe HI mode should bypass the regulator. Play with adjustment and see what it does?
We had regulator DIY on one of this forum, so do a search. I am one of those lucky guys that never had that problem

mcanix

fabbrisd1,
I wish it was a C32! I had one for a few years and it was the funnest car I ever had until the transmission started beating me to death. This one is a 96 W202 C280 Sport.

Kajtel1,
Ok. Which "adjustment" are you referring to? With the blower on low, I selected all of the modes, i.e. auto, footwell, windshield, center, recirc and defrost and was able to listen to all of the actuators.

On a 97 W210 I had, it had a short that I narrowed down to the blower regulator. After discovering that I would have to replace the blower and cover due to the "upgraded" regulator I did the mod in which I soldered a regulator from an S class into the existing harness. Saved about $750.00. Thanks to you both!

kajtek1

I think def mode puts it automatically on Hi, but if you set it manually to the windshield, than you can use +- to change the blower speed.
That should tell if the regulator is doing its job.
Again, I never had to deal with this issue myself, so check for blower topics.

mcanix

Gotcha. Thanks!

mcanix

Back to the W210, I got back into town and replaced the evap. temp. sensor and SUCCESS! I initially tried to replace it by pulling the cluster but had no luck. I rechecked the sensor values this morning and they are as follows-
1. In car temp. sensor 25
2. Outside temp. sensor 28
3. Lt. side heat exchanger temp. sensor 10
4. Rt. side heat exchanger temp. sensor 11
5. Evap temp. sensor 10
6. Coolant temp sensor 34
7. Refrigerant pressure 15
8. Refrigerant temp. sensor 31

Thanks again to Kajtek1 and fabbrisd1 for all your help with this.

kajtek1

To check sensors calibration you should do it in the morning before sun warms the car and engine off.
Sensors do have loose tolerance, but when 1 shows 10' different than others - that should be kept eye on.
Glad to hear you have cool car again

mcanix

I've been tied up with a bunch of other things but believe it or not, the C280 had a completely plugged cabin filter and now it blows like it should.

New problem with the E320. After a few minutes of driving, when accelerating, the center vent airflow is diverted to the defrost ducts. As always I've searched the forums and opinions are all over the place. I've done the flap test and all seemed to operate properly. I "T'd" in a vacuum gauge between the vacuum distributor in the passenger footwell and the vacuum valve that controls all of the flaps. At idle the vacuum stays around 15 inHg. At speed with light throttle pressure it is 17. Under moderate acceleration it drops to below 10 and when it gets to 5 the flap diverts to defrost. When letting up on the throttle it returns to normal. Off the top of my head I was thinking maybe the dashpot?

kajtek1

At WOT the intake has no vacuum and that is why car system has vacuum reservoir to supply some power to flappers for those moments.
Looks like your car develop a leak big enough to drain the reservoir on short note.
The truth is that access to AC elements is a nightmare and for example my father's 1987 car has flappers disabled for years.
It blows the air via defrost and side vents, while we seldom use heating.
But before you jump big guns, check vacuum hoses around the intake manifold and at the firewall.

mcanix

I was thinking that it was a leak but it appears that this car doesn't have a reservoir but has something called a dashpot.