Joe Hogan

Hello all,

Need a little help.

2003 CLK500 - AC blows hot when parked, but will cool down (but not frigidly) while driving.

At first, I figured I had low refrigerant, so I purchased a few cans. At idle, the car won't really take any refrigerant. So, I started googling, and found the method for getting the AC codes from the AC control unit. Here is what I got.

After 15 minutes of driving, then about 2 minutes of idle.
0 = 105
1 = 105
2 = 95
3 = 156
4 = 158
5 = 165
6 = 208
7 = 15
8 = 154

( I have the full list if needed)

I also tried a reset (recycle+defrost). The ligths both blinked, alternately, and I could feel air cycling from the defroster, to vents, to floor, and around again. But after a few minutes, the lights continued blinking, and the airflow kept cycling between the different zones.

The reset suggests I might have a bad actuator for a damper, however, would I still get cool air while driving?

Other considerations: I do have a damaged ambient air temo sensor in the bumper, so it currently reads 185 deg, but I'm not sure if that has anything to do with the AC system...

Any thoughts? A buddy (about 2 months ago) did put gauges on the ac system and thought that I was a little low, but not sure why the low side wouldn't take too much r134. It did take a little, but not much, and the pressure was reading in the red, and doesn't really fluctuate.

Thanks in advance,
Joe

Rudeney

Hi Joe, I'm not sure how to decode those readout values, but I think they are temperature readings from the various sensors. You really need to get codes scanned from the ACC to know what's going on.

As for the symptom, this could be a damper problem if it's letting heat into the ducts. Or, it could be a bad expansion valve, or compressor, or a low refrigerant charge. Pulling codes would tell you more.

Note that when using gauges, the pressure is based on ambient temperatures. If it's cold outside, you may not be able to get it to take refrigerant. It's actually best to recharge a system when it's very hot.

Joe Hogan

I figured it out. Looks like buddy had a bad gauge on the low side of his gauge set. Looking at it with another gauge, low side was over pressure, so pretty sure the high/low switch was triggered. Also some air in the system when we did a bleed. Got it back to a normal pressure, and ac cooled down at idle immediately.

I still think I need an AC flush, though, as it does get cold, but not frigid. My suburban will freeze you out on low. Is this typical for a W209?

Thanks,

sailorben

Nope, in both CLKs I have had, they've been excellent. I've not touched the system. I always leave the AC on, just to condition the air constantly. But as soon as the dial is on low I can have it ice-cold. Even with the dual-zone hottest on one side and lowest on the other side, I can get both extremes.
It can take a few seconds for the fan speed to ramp up fully for full blast. Same with the demister. Takes a moment for the air con to kick in full, then the fan speed ramps up.

Rudeney

Yeah, the only MBZ I've had with substandard AC was the MY2001 ML320. The next model year, they increased the size of the compressor.

MarcusF

@Joe
#3 and #4 are the temperature sensor readings for the left and right heater cores. #5 is the temperature at the evap sensor and #6 is the coolant temp. I doubt you'll see ultra cold air with the heater cores that hot. Also, #1 is the in-car sensor and it may be broken or filthy (in a 208 there's a small fan that blows air and dust over it). On my car the external temperature sensor was an important part.

I'd clean the internal temp sensor (it's in the overhead light assembly on a 208), replace the ambient temperature sensor (they're $15), and clean the duo valve. The duo valve controls flow to the heater cores and there are YouTube videos that explain how to clean them. Caveat: everything I've mentioned is correct for a 208 and may the same on a 209.