Mercedes-Benz Forum banner

1 - 3 of 3 Posts

28 Posts
Discussion Starter #1
ok..... ac is not blowing cold air.... i took it for a check up they vacuumed the system and added new freon and still nothing.....the gauges showed: high would go down when reving and low would go up when reving... compressor is turning....this mechanic is not sure whats wrong as he doesnt have too much experience with mercs, he told me to get second opinion.

i did REST diagnostic test , readings are as follows:

1. 96
2. 119
3. 98
4. 98
5. 97
6. 207
7. 13
8. 99
10. 2.0
20. 2.2
21. 600
22. 0
23. 0
24. 14
40. 8
41. 5

please help me out as its hot here...

thank you

2000 CLK430 2010 S550 4matic
532 Posts
I saw your post this weekend and I had to go to my office and check the values for your sensors.

If the gas is correct and its good that you took it to someone to get a proper charge there are a couple of things that I see wrong.

First the sensor 21 is reporting 600 which is clearly wrong - this is your vehicle speed sensor and should report the mph value. So something is wrong there - would it put the AC system into limp mode or shut it off after a few minutes - maybe. I'd replace that or have that checked out -

Second - your blower control voltage seems low - was the fan (inside) when you did the test? Should be more than 2.2V's - but maybe not if the fan was set low.

If the compressor is working and the entry line feels cold - going into the car - also check and feel under the dash just under the glovebox and feel the evaporator box and see if its cold. You may have a duovalve that stuck open so its letting in the hot coolant into the airbox - mixing with the cold and not getting the air exiting out the vents cold. If you can't feel it cold - you may have to remove the cabin air filter and feel in the box. Alternatively if you have decent humidity there should be some condensation dripping out of the car.

If its stuck or broken its a pretty easy fix - there are tons of posts here on how to do that.

Report back.
1 - 3 of 3 Posts