A/C intermittent problem with the air flow
 

Hi all,

I have a SL320 from 1998.

The problem is related with the A/C. Sometimes, the air flow decrease (the power), but I don't touch any button of the console (and it's not on AUTO mode). After a few minutes or seconds, the air flow increases automatically, to the correct flow power... I don't know why is the reason... probably the filter is dirty... I don't know!!!!!

It happens when the car stops or when the car starts to run. It must be due to the movement of the car, when taking a curve or something thus.

The problem is not related with the AUTO button. I put the power of the air flow to the MAX position, but sometimes the flow changes (decrease) for 5 or 10 seconds, between low speed and high speed. It is like something is covering the tube... may be a leaf???????

Could help me somebody?

Thank you very much in advance.
Regards,
Jorge Ruano

Hi,

I think the motor is OK. Probably are the valves.

Today I've observed that when I press the air re-cycling button, sometimes nothing happens and sometimes the airflow is greater. Do you think that the valves are involved in the air re-cycle circuit? Or, may be the air filter?

I think that the air filter is only for the external air, and when the air re-cyling button is pressed, the air doesn't pass for the air filter... isn't it?

Where are the valves and where are the air filter? Can I clean the valves and/or the air filter? Is it easy to do?

Thank you in advance and regards,
Jorge Ruano

I have more information about the problem:

When I ignite the engine and I turn on the A/C I put the maximum power of the flow (I touch the button for the flow speed to the maximum). The A/C works fine, with the maximum speed of the flow... but after 5 or 10 minutes, the speed of the air flow decreases, I don't touch any button, I don't touch nothing:confused: :confused: :confused: :confused: :confused: .

The A/C decreases the speed automatically after a few minutes but I don't know the reason. After it, I can't increase the speed of the flow to the maximum power. The display of the flow power marks the maximum power, but It isn't true, because it decreases, but the display marks the maximum power... why????

Thank you in advance.
Regards

same problem here????

The 129, 140 chasis have this problem. It is the evaporator freezing up in high humidity. When the layer of ice formers it blocks air flow. That's at least the most common problem

I have changed the evaporator temperature sensor (Part number: A 210 830 07 72 Temperature sensor).

In the A/C display, I put the low tempoerature ("LO") for the most cold, and I put the maximun air flow, for the most power, and the A/C works better with the new sensor, but it continues failing because it continues cutting the air flow, more time in cutting it takes but it finishes it cutting. Before, it fails in 4 or 5 minutes, and now, it fails in 15 o 20 min. Works better, but...

I observe that now, when I press the re-cycling air button, the air flow works with the maximum power, and it works fine, but only if I pressed the re-cyling air button.

I don't know what can I do and what will be failing now... or if it is the normal operation of the A/C in R129.

Some idea?

Check to make sure your evap drains are clear, and try blending the air a little. Put the temp on say 65-68, or 18-20 rather than low. It isn't uncommon in the high humididty to freeze over the evap. The 129/140 hold enough zone to cool two cars. Beautiful car by the way, Those 140 chasiss are my choice of car, 30+ MPG and all the power in the 320. Just remember, DONT SLAM THE DOORS. I hate adjusting the micro switches.

OK, but where are de evap drains??????????

Just above the transmission bell housing, You will see two rubber hose looking things on each side that are molded to close like a "mouth." Does that make sense? The hoses are pretty big, maybe 36 mm in size or so, give or take. You may need to put it on a rack

I don't know exactly... Are they underneath the steering wheel?

Please, I need help to find the drains...