[55Benz]

Hi Everyone. Last week while driving A/c air suddenly got hot. I purchase refrigerant and followed the instructions on resetting after the ec illuminated.
I hastily reset before writing down the code. Compressor come on but has occasionally for periods of less than a minute. I've tried to quickly add refrigerant while it's on with no success. Also according to my gauge the pressure on the low side quickly climbs when I try to add 134. This could be due to reading a value after the compressor has stopped running. Maybe? The pressure on low side according to my gauge was around 50psi. I let some gas out of the valve to lower it. I reduced it to about 10 psi. tried again to add when comp. briefly came on but no luck. Compressor only seems to come on when the car has not been running for 2 or more hours and I could get it or the aux fans to come on at all today. Fans turn freely by hand with no noted roughness. Fuses are all good in the engine compartment. I've run the diagnostics and will list their values below. Also I've been driving the car hoping the original fault will reappear but it has not and the ec light has not returned. Sorry I posted extra values. Thanks in advance for any help. It's hot here in Wilmington NC!
1 - 82
2 -78
3 -87
4 -87
5 -134
6 -94
7 -03
8 -82
9 -27
10-2.3
11-1.5
12-4.3
20-3.2
21-32
22-00
23-32
24-11.6
40-164
41-85
42-08
43-136

 

[mrboca]

Hello

Obviously you took the readings with the engine off (from the battery reading). You need to take readings with the engine running and a/c working.

Coming to your real problem, your evaporator sensor is bad, and that is why you get warm air after a while. The evap core is freezing restricting coolness transfer to the airstream..

Do not play with the refrigerant. Fix the evap temperature sensor issue first, and then you can add refrigerant as needed.

And it is good that you posted the extra values. Otherwise how would we know what your battery voltage was and determine whether the car was running or not #24 = 11.6V

 

[55Benz]

Thanks for your reply. Actually a/c worked perfectly since I've had the car; about 2 years. It just suddenly got warm last week, and hasn't been cold since.
Will evap sensor keep compressor and fans from turning on? I guess I can't get some important readings without the compressor operating.
Thanks again.

 

[mrboca]

Check the fault codes from the hidden menu on your a/c control unit.

Follow the link to retrieve the codes, record post them here, and then reset the codes per instructions. You need to clear the codes related to refrigerant fill for the compressor to run, so you can put more refrigerant.

STAR TekInfo

When the system is stable, engine cooled down overnight and the coolant / refrigerant temperature is close to outside air temperature, the refrigerant pressures in psi on high / low side should be about the same as your outside temperature. If you have 80 degrees refrigerant temp (#8 in the list) the pressure should be about 80 psi or between 5 and 6 bars. You have low refrigerant level it seems.

Once you clear the codes the compressor should run for you to put some refrigerant (make sure you purge the air out of the manifold / charge hose prior to fill to prevent letting air into the system.

Your fans should start running when the high side pressure is about 15 bars (#7 in your list).

You do not need the compressor running to get the fault codes.

The evap sensor will not affect the compressor running up to a certain point. Your compressor should start running with a bad sensor but soon the evap core will freeze over and you will get warm air.

 

[55Benz]

Hi again.
Yeah as I mentioned earlier I screwed up in the beginning and didn't write down the fault codes when I reset the codes to get rid of my ec light and hopefully get my compressor to run again. I currently have no stored codes after running for a week. My ec light has not come back on, and my compressor sputtered on a couple of times for less than a minute and wont come on at all now. I guess I'll try turning the compressor pulley and see how it feels. Is there a test mode for the aux fan in the climate control unit? I used to have a Porsche that I could test fans with my scan tool.

 

[mrboca]

Sure, you can press BOTH AUTO buttons for 15 to 20 seconds simultaneously and hold, the fans should come on at full speed.

If you have a scan tool that can access the 38 pin connector, and can access the a/c module, you can turn on the fan(s) at different speed stages.

Your compressor is not turning on because you have too little refrigerant. You can try the version coding for the controller to ignore the refrigerant pressure, so the compressor should turn on after you set the P2 to read 152 in the attached.

STAR TekInfo

By looking at your #43 (another benefit of providing the whole list ), the value is 136 which indicates that the controller check the refrigerant level and switches off the compressor if the refrigerant is low. This is really a redundant feature as your compressor has built-in mechanisms to protect itself from low refrigerant levels.

Follow the instructions to add 16 to 136 which makes it 152. So after this procedure, when you list your sensor values #43 should read 152.

Then you can charge the refrigerant once the compressor is running. If the compressor still does not want to run, let us know .

A good scanner should be able to tell you the status of the compressor running or not.

 

[55Benz]

Hello Again,
Ok, I set P-2 to read 152 and restarted, compressor came on and I added most of a 12 can of 134. I though can was empty but had approx an oz left. Still no cold air and compressor shut off occasionally but will come on with some regularity when I start the engine. I've tried to add more 134 when compressor is running but it will not take more. The ec light has not come on again, so I can't get any fault codes. When I check no codes are showing. I tested the high fans and they came on full blast. I did get values with motor and compressor running throughout the range. Any ideas? Thanks a ton.
1 -103
2 -94
3 -141
4 -103
5 -143
6 -172
7 -06
8 -105
9 -27
10-5.2
11-1.4
12-4.1
20-3.2
21-42
22-00
23-32
24-12.0
40-164
41-85
42-10
43-152

 

[illstplaya]

If those are the numbers when the engine is running and climate control set to the lowest temp then I see a few things wrong. Battery voltage is too low. Left heater core temp is too high. Evaporator temp sensor is showing the temp to be very high.

 

[mrboca]

1) replace your evap core temperature sensor.

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=automotive&field-keywords=2108300772

You do not need to buy the OEM. Just buy the one that has good reviews and price.

2) You may have a sticking duovalve. You can address it after you get the evap temp sensor replaced.

3) Was the car and a/c running when you took the readings ?

4) Do not add more refrigerant until you address the evap temp sensor issue. One step at a time.

 

[55Benz]

Yes the car was running and the compressor was on for the last readings. Re: voltage: I replaced the alternator about 6 months ago and the voltage regulator is a little funny at idle but is ok over 700 rpm's. I've been meaning to replace with the one from the last alternator and use the new brush assembly only. Also the car made a loud vibration/roar on acceleration today a couple times, only when Ac was on. I pulled over and could not get the same sound when not in motion.

 

[mrboca]

Forget the a/c, and fix your charging circuits first.. While idling, you should see a minimum of 13.1-13.2V at #24 and you have 12V. Your car was running on the battery, not on the alternator. And I would not expect the things work properly, especially when you turn the a/c on with high current consumers like the blower and the electrical fan. Low voltage and charging problems can affect many modules of your car.

 

[55Benz]

Hello again,
Is it at all possible the evap core temp is actually that high? I heard a very low squeal when compressor started this evening. Not loud like a power steering squeal and only for a second but not normal. While driving today with ac on I heard a bad vibration/roar under acceleration. Stopped when ac turned off. Oddly I could not reproduce the same sound when I pulled over by revving the engine slightly. Even after the noise the ec light has not returned. My code reader is basic and I don't think it will allow me to pull compressor data.

 

[SkippyJasper]

The vibration/roar MIGHT be the cooling fans coming on at full blast or the compressor failing. In my '98 E320 when the compressor locked up there was a brief squeal followed by a short tug on the motor.
Check to see if the compressor is still turning.
Skippy

 

[mrboca]

The evap core temperature in your case should be around the same as #8 which is a bit more than 100 degrees F. It is the temp sensor that gives the false readings.

Check your serpentine belt , tensioner and the idler pulley. If your compressor is not able to turn with the clutch engaged, the belt will slip and generates heat on the pulley, and there is a thermal fuse inside the clutch mechanism which will open to cut the power to the clutch coil, and it will disengage the clutch. This will protect the belt from snapping off.

You should be able to turn the compressor off by pressing the EC button. When the red light comes up the compressor is turned off, and pressing the EC again will turn the red EC light off and the compressor should turn on.

 

[55Benz]

Hi Guys,
I went ahead and ordered an evap sensor today. That sounds like the best starting point. The compressor is still turning ok. I think I replaced the idler pulley last year when I replaced the alternator belt and vibration damper. I didn't check it today. No garage at the moment and it rained all day. I'll update soon.
Thanks for your input.

 

[55Benz]

Hi Everyone,
I replaced my evap sensor today. My compressor is still running since I bumped P-2 up to 152 the other day. I've been putting it on ec when I'm driving so I don't damage anything further. I did not attempt to add more 134 today because according to my gauge pressure on the low side is at 100psi. Here are today's values.
1-93
2-85
3-134
4-93
5-89
6-166
7-05
8-94
9-27
10-4.3
11-1.4
12-3.9
20-3.2
21-49
22-00
23-32
24-13.1
40-164
41-85
42-10
43-152
Any ideas?
Thanks

 

[mrboca]

Is low side 100 psi with the engine running ? It would make almost 7 bars which is higher than the high side (5 bars) ? Are you sure the compressor is running ?

If the systems runs properly the low pressure side should be about 2 bars.

Follow the tests in the attached. Especially test condition 3 (with the temp setting set to HI.......rpm 1500. Does your low pressure gauge pulsate ????

STAR TekInfo

 

[55Benz]

Hi,
Yes I'm getting 100 Psi with car and compressor running. My gauge works similarly to a dial type tire gauge. It holds the peak pressure until released. What would account for the difference in my low pressure reading of 100 psi. vs. value #7- 05 bars. Is value #7 low side, high side or a different pressure? I tried tapping gently on the duo-valve with my screwdriver handle with no change. I don't have a Fluke meter with a thermocoupler. Assuming my gauge is correct; my low side would simply not take 134 if I attempted to add right? I could attempt to add, compressor, recirc, on temp low and see to rule out possible gauge error. If the can doesn't get cold I'll know it's not receiving the 134....

 

[SkippyJasper]

55Benz,
I have found that exercising the duo-valve will often fix it. By exercise I mean to raise both sides to max heat, let it get there, and then lower to max cold.
Of course you can take the valve apart and find some grunge to clean, but I'd try the exercise path to see if you can stabilize the left side (#3 on the readout).
Skippy

 

[55Benz]

Thanks,
I'll give it a workout!