When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm almost done with restoring my W210 to factory condition and it's been a huge amount of labor, parts and love but it was oh so well worth it.
However, I seem to have a bit of an issue with the A/C, I noticed that it would stop blowing extremely cold air when idling for more than a minute of two and would start blowing ice cold as soon as RPMs move up.
I've pulled codes from the AC unit in the morning in a parking as follows:
01: 25
02: 26
03: 25
04: 25
05: 24
(In Celsius) and these make perfect sense. I monitored 05 (Evap Temp) and noticed that the system would cool all the way down to 00 Celsius then the pressure in sensor 07 drops from 16/17 all the way down to 10. This is accompanied by an increase of 05 all the way to 20 Degrees Celsius before dropping again to 00 when I move from a standstill.
I've read this could be alternator pulley slipping causing the compressor to turn off, control valve on compressor, Evap temp sensor (readings are accurate).
Could it be a faulty unit? I can try another one if there's a possibility that it can be the cause.
I've also read on WIS the following: (as a solution to A/C coming on and off)
If changing the Compressor fixes this I would gladly fo it.
Genuine Mercedes parts installed related to A/C in the past year (to rule out problems) & Mercedes dealer installation.
- New Duo Valve
- A/C Refill
- New dust & charcoal filters
- Cleaned Heater Blower and A/C
- New A/C control unit
It blows ice cold when it's cooling, but if you're idling too long, pressing the EC button on and off cools the evap immensely and stays ice cold until you start moving again.
I hope that's enough information for an educated guess!
Much appreciated
Thanks! Forgot to mention that I had checked error codes and found none on the pushbutton unit, also had a dealer scanner take a look at it with the same outcome.
What do you mean exactly by "precise"? The only thing I haven't done is the flap testing.
You need to do 2 sensor readouts per notes on the site.
Morning readout checks sensor calibration, when "hot" readout checks compressor performance.
Sensors 1-8 are important.
You can replace evaporator sensor per dealer's check, but takes 90 seconds to confirm that DIY.
You need to do 2 sensor readouts per notes on the site.
Morning readout checks sensor calibration, when "hot" readout checks compressor performance.
Sensors 1-8 are important.
You can replace evaporator sensor per dealer's check, but takes 90 seconds to confirm that DIY.
Checked what readouts you wanted based on your previous posts and here goes:
In the last situation, if I click on the EC button, wait around 5 seconds then press it again, the system starts blowing ice cold and all temps drop accordingly with an increase in pressure in #7.
Does your car have the electric cooling fan? Does it speed up at idle when the A/Cis on? If not you will experience the symptoms you mention. There is a controller for that fan.
In the last situation, if I click on the EC button, wait around 5 seconds then press it again, the system starts blowing ice cold and all temps drop accordingly with an increase in pressure in #7.
Did you erase all codes?
Your system is checking calibration OK and in 3rd readout shows decent performance with evaporator coming to 5C, but seems later computer cut the compressor off for unseen reason although your refrigerant shows a tad low.
Make sure all codes are clear and repeat hot test while leaving pressure #7 on display. Observe how the pressure changes few minutes after starting car with hot cabin.
The thermostats should be set at normal level in 20's for C or 70's of F
Does your car have the electric cooling fan? Does it speed up at idle when the A/Cis on? If not you will experience the symptoms you mention. There is a controller for that fan.
This is the setup I have, not the one with two adjacent fans. However, if I hold both Auto buttons on the AC unit for a few seconds I hear a fan spinning but that doesn't affect the cooling at all. The symptoms also appear when using cruise control on the highway. It seems that whenever the engine is not working hard ice-cold air takes a backseat. Oddly enough, when I was waiting in a parking lot I discovered that pressing the EC button twice would re-engage the compressor at max, resulting in ice cold air.
Did you erase all codes?
Your system is checking calibration OK and in 3rd readout shows decent performance with evaporator coming to 5C, but seems later computer cut the compressor off for unseen reason although your refrigerant shows a tad low.
Make sure all codes are clear and repeat hot test while leaving pressure #7 on display. Observe how the pressure changes few minutes after starting car with hot cabin.
The thermostats should be set at normal level in 20's for C or 70's of F
Will do the test, by thermostats you mean the air temp on the AC unit?
No codes yet since this was a brand new unit from Mercedes. Evaporator also comes down to 01/00 Degrees when LO is set on both sides. The system was behaving like this before and after the charging. The compressor can hits 17 bars when temp is set to LO as well.
Those readings were done with temp of 16 Degrees C at AC unit on both sides.
I should mention that the compressor doesn't seem to shutoff completely because I still feel a vibration at idle that goes away when I turn off the compressor with the EC button. However, it is worth noting that the vibration is stronger when the compressor is fully engaged compared than when it is blowing only slightly cool air.
Should I just go ahead and replace the compressor?
You are on a wild goose chase---the fan is programmed to come on when the coolant temp and or refrig temp is to high------you have none of those conditions.
Your issue is number 5 evap temp and number 7 refrig pressure-------5 should be between 15 to 20 to low and you get icing; 7 should be 15 to 17 bar.
I would suggest that you put a set a gauges on the car------does the high side needle fluctuate wildly???
Would need to pass by the dealership to do that then. Wouldn't this have shown when the system was professionally recharged using a machine btw?
I am not trying to argue with forum clown, but 15 to 20C = 60-70F.
Evaporator at this temperatures will never cool down the car.
In hot weather #7 pressure should be in 20's.
At this point I'd say it is safe to add a can of r134
I am not trying to argue with forum clown, but 15 to 20C = 60-70F.
Evaporator at this temperatures will never cool down the car.
In hot weather #7 pressure should be in 20's.
At this point I'd say it is safe to add a can of r134
Got the A/C refilled at the Merc dealership a few weeks ago, it was half full, last refill was years ago. Machine went through vacuum leak checks and filled/refilled the system many times around.
On a hot day I noticed the compressor would hit 18 at sensor #7 at which ICE cold air would blow in conjunction with an evap sensor showing 2-3 Degrees Celsius. It was very clear than when the evap was at 15-20 Degrees Celsuis, the cooling is not nearly as effective as to when the evap is at 5 Degrees.
(In Celsius) and these make perfect sense. I monitored 05 (Evap Temp) and noticed that the system would cool all the way down to 00 Celsius then the pressure in sensor 07 drops from 16/17 all the way down to 10. This is accompanied by an increase of 05 all the way to 20 Degrees Celsius before dropping again to 00 when I move from a standstill.
I've read this could be alternator pulley slipping causing the compressor to turn off, control valve on compressor, Evap temp sensor (readings are accurate).
I recently replaced my entire system front to back, every piece sans the hoses that were in good shape. The variable bar figures your compressor is outputting is normal. It rises at idle and falls during movement as more air runs through the condenser.
At idle, my evap sensors sometimes creeps up in to the high 40s (8C). My belief is that at a prolonged stop, the heat from my radiator sort of heat soaks the condenser but my numbers do not rise as high as yours. My radiator is new as well but I dont have a working fan clutch to draw excess heat away, My car operates within normal temps with blue antifreeze.
Seems like the freon is low or not quite enough to throw codes but affects cooling.
Last edited by Tall Giraffe; Jun 26, 2019 at 02:02 PM.
Well what do you know, I redid the test and manually activated the Fan when idling (held both Auto buttons together) , temps remained ice cold and the compressor was showing 20 on sensor #7!
Outside temperature was 36 C, engine temperature doesn't rise above 85 with the fan and AC on.
Those numbers show good performance, but they show only part of the system.
Are you still having occasional problems?
When the AUX fan is engaged the issue does not present itself at all. Should the aux fan controller be replaced then? Shows 0V on Sensor #20 at all times and never comes on. When I force enable it, it goes to 10V directly and cooling is exceptional!
I think such issue should be troubleshoot with advanced scanner. I would clean all the connections before jumping the gun.
If the part is cheap, swapping it might be good call, but it is always some gamble.
I think such issue should be troubleshoot with advanced scanner. I would clean all the connections before jumping the gun.
If the part is cheap, swapping it might be good call, but it is always some gamble.
More updates:
Took a long (2h trip) with the fan forced on. #7 was on 20 at all times but Evap sensor on #5 still went up and down between 18/19 and 01/02 Degrees Celsius.
I've ordered the Evap sensor to be safe. WIS also mentions that intermittent cooling could be due to a faulty pressure sensor on the compressor that would communicate erroneous data to the AC controller.
A test for this is recommended by WIS and documented.
Dealership appointment taken, will keep you posted.
I think such issue should be troubleshoot with advanced scanner. I would clean all the connections before jumping the gun.
If the part is cheap, swapping it might be good call, but it is always some gamble.
More updates:
Took a long (2h trip) with the fan forced on. #7 was on 20 at all times but Evap sensor on #5 still went up and down between 18/19 and 01/02 Degrees Celsius.
I've ordered the Evap sensor to be safe. WIS also mentions that intermittent cooling could be due to a faulty pressure sensor on the compressor that would communicate erroneous data to the AC controller.
A test for this is recommended by WIS and documented.
Dealership appointment taken, will keep you posted.
If you were here in the US - the evap temp sensor (China knockoff) is cheap USD $10 and EZ DIY install.. MB part about USD$55 - no "workshop appt" needed for evap sensor switch out and no codes to clear.
Yes - evap sensor can go wonkey .. "normally" when evap tempo sensor goes you get "impossible" temp readings on climate control diagnosis..
What you mean by "up and down"?
Was it 1 minute intervals, or 1 second intervals?
When minute changes might indicate the computer changing the demand, 1 second changes would indicate bad electrical.
What you mean by "up and down"?
Was it 1 minute intervals, or 1 second intervals?
When minute changes might indicate the computer changing the demand, 1 second changes would indicate bad electrical.
After first start it will quickly go down to 02 Degrees Celsius, hold it for a minute or two then the temperature rises again to 18 Degrees Celsius within a minute or two. (Evap Temp - #5)
I noticed that my battery voltage was around 13V all the time and lower on idle (12.5V), could that affect the AC in any way?
If you were here in the US - the evap temp sensor (China knockoff) is cheap USD $10 and EZ DIY install.. MB part about USD$55 - no "workshop appt" needed for evap sensor switch out and no codes to clear.
Yes - evap sensor can go wonkey .. "normally" when evap tempo sensor goes you get "impossible" temp readings on climate control diagnosis..
Ordered the MB Genuine Evap part, will install it as soon as it gets here. Part was around 100$, will check list price and argue accordingly.
After first start it will quickly go down to 02 Degrees Celsius, hold it for a minute or two then the temperature rises again to 18 Degrees Celsius within a minute or two. (Evap Temp - #5)
I noticed that my battery voltage was around 13V all the time and lower on idle (12.5V), could that affect the AC in any way?
Thanks!
Not sure, but computer monitors the voltage as well and quite possible that faulty charging system makes it killing AC.
And yes, minute intervals indicate that it is computer fluctuating the system, not a sensor fault. Confirm that by observing pressure #7. If it fluctuates with the same intervals, you know the sensor is good.
So start with fixing confirmed problem, what is your charging system. Voltage should stay at 13.5V read on cliimatronic, or 13.9V on battery clamps. If not- replace voltage regulator.
Not sure, but computer monitors the voltage as well and quite possible that faulty charging system makes it killing AC.
And yes, minute intervals indicate that it is computer fluctuating the system, not a sensor fault. Confirm that by observing pressure #7. If it fluctuates with the same intervals, you know the sensor is good.
So start with fixing confirmed problem, what is your charging system. Voltage should stay at 13.5V read on cliimatronic, or 13.9V on battery clamps. If not- replace voltage regulator.
Ordered a new Alternator from Mercedes, part # A 010 154 46 02 (14V 90A), will update you once replaced. Current charging system never goes above 13V on Climatronic unit, also, I noticed that when the fan was set to run at full speed (10V), voltage would drop to 12.5/12.6V consistently until the fan was forced off.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Slideshow: A one-of-one U.S.-spec Mercedes-Benz SLR McLaren Roadster became even rarer after a factory-backed transformation at McLaren's headquarters.
