W210 AC gets warmer with acceleration?

[treetops]

Hi folks, I've got an ac issue that's new in the last month. The temps at the vents feel like the system/ compressor has shut off when I accelerate or rev over 2K. The ACC digital readout values for 3-5 show a corresponding temp increase of about 20 degree bump at the same time. After acceleration, 30 seconds or so, the vents get cooler and the 3-5 value return to the lower 40s F.

I do have a faulty duo-valve, but that's relatively under control and not a part of this issue. I believe there is enough R134 in the system and other than when I accelerate the ac works great.

I believe there may be a vacuum control/issue that could shut the compressor off in his instance but not sure if that's the cause. Any ideas?

Here are some ACC values

1. 85. , 78
2 94. , 82
3 62. , 40
4 64. , 40
5 57, 39
6 173 177
7 17. , 15
8 138, 137

[jay_bob]

Parameter 8 (high side temperature in deg F) seems high to me.

My temperature runs more to the 90s to 110s.

Pressure looks reasonable, parameter 7, 15 bar = 225 psi, 17 bar = 255 psi

I am not an ac expert but maybe one of the others on here will know what to think of this.

Here is a quick reference on the parameters:
1 - cabin temperature (sensor in the overhead control panel by the dome light)
2 - intake air temperature (sensor in the intake plenum) note that this temperature may or may not equal the ambient temperature that is sensed in the bumper and displayed in the instrument cluster. If the car has been parked overnight and the sun is not shining on the car, both numbers are likely equal. But on the road the two sensors see very different environments - the plenum draws hot underhood air and the bumper sensor gets radiation from the road and exhaust from cars in front.
3 - left heat core temperature
4 - right heat core temperature, these sensors are on the face of the heat core
3 and 4 can be used to rule out a leaking duo valve, if 3 and 4 are equal or less than 2, then the duo valve cannot be leaking since the heat core is no warmer than the incoming air. Best to do this on an extended highway drive in the evening in EC mode so the system is at equilibrium and the sun and the a/c don't skew the results.
5 - evaporator leaving air temperature - sensor in the air stream on the drivers side of the evaporator about an inch off the surface of the evaporator (the air flow comes from the passenger side from the blower, across the back of the air box closest to the firewall, goes through the evaporator, then the heat core, and then out the vents).
6 - engine coolant temperature - sensor in the cylinder head
7 - refrigerant high side pressure - in Bar (1 bar = 14.7 psi) - sensed at the receiver dryer
8 - refrigerant high side temperature - sensed at the receiver dryer
9 - unused
10 - blower regulator reference voltage *10 - this goes to the blower regulator and tells the fan how fast to run - 0 to 6 V is stopped to full speed
11 - emissions sensor - located in the intake plenum - a relative measure of hydrocarbon and CO content in the intake air - engages auto recirculate and carbon filter
12 - sun sensor - top of the dash - 4.2 is totally dark 2.0 full sun
20 - aux fan regulator reference signal
21 - engine rpm *100 - I wonder if this is for gas engines only, never seen this number mean anything on my E300, the diesel and gas rpm sensing is totally different
22 - vehicle speed
23 - instrument illumination voltage - 211 is full scale
24 - Vehicle battery voltage less 0.7 V (13.0 V on display is actually 13.7 V bat)
40 - software version
41 - hardware version

[treetops]

Thanks Jay_Bob. Does the W210 ac system rely on a vacuum signal or lack thereof when operating? I know my question is not clear, but Im thinkingwhat I am experiencing is a something along these lines.

Any hints on this?

[leathermang]

Why don't you or someone put gauges on the AC system and see what it says during the conditions you are having strange behavior at ?

[pimpernell]

Originally Posted by treetops

Hi folks, I've got an ac issue that's new in the last month. The temps at the vents feel like the system/ compressor has shut off when I accelerate or rev over 2K. The ACC digital readout values for 3-5 show a corresponding temp increase of about 20 degree bump at the same time. After acceleration, 30 seconds or so, the vents get cooler and the 3-5 value return to the lower 40s F.

I do have a faulty duo-valve, but that's relatively under control and not a part of this issue. I believe there is enough R134 in the system and other than when I accelerate the ac works great.

I believe there may be a vacuum control/issue that could shut the compressor off in his instance but not sure if that's the cause. Any ideas?

Here are some ACC values

1. 85. , 78
2 94. , 82
3 62. , 40
4 64. , 40
5 57, 39
6 173 177
7 17. , 15
8 138, 137

I am no expert regarding AC, but here is a page that can give you some leads regarding your issues.


http://www.mercedesmedic.com/ac/

[compu_85]

If you keep the car above 2000 rpm does it start cooling again? The computer might shut the compressor off momentarily when you accelerate to give more power to the wheels. I'd venture that if you notice a vent temp difference the charge is low or the compressor is worn.

-J

[treetops]

Originally Posted by compu_85

If you keep the car above 2000 rpm does it start cooling again? The computer might shut the compressor off momentarily when you accelerate to give more power to the wheels. I'd venture that if you notice a vent temp difference the charge is low or the compressor is worn.

-J

It depends on rpm, I did an up hill test in 3rd gear with rpm in the high 2000s with the ACC menu up, ambient 83F, #3-4 increased about 4 degrees, #5 about 8(from the low 40s to 51-52) and #7 dropped to about 9-10 from 15-17. So Id have to say this seems to happen mostly above 3K rpm.

I dont have gauges, but will ask my mech to run some tests when the car is in for inspection in the next week or so.

Thanks for all the input....hoping the compressor is not showing signs of its age-which is unknown to me.

Probably low on freon. Forget about trying to read parameters through the head unit, your over complicating a simple system. I dont care what kind of gizmos and gadgets are attached to the HVAC box in the dash, an A/C system is pretty much a compressor, condenser, orifice tube or expansion valve, and evaporator.... thats it... no gadgets or gizmos.

Get a bread baking thermometer 0F-250F, and stick it in a center vent. Cruising at a steady speed, you should see 35F-40F from the vent in a HEALTHY A/C system. IF not....then either low on Freon, compressor is bad, bad temp actuator, or a bad expansion valve. PERIOD.....

I work on everything from ford escorts to S600 Bi-turbo, and I look PAST anyhting overly complicated...and shoot right for the simple issues. Usually you find the problem.