I have a 1998 ML320 with a little more above 100,000 miles. Lately I am experiencing a strangs thing that is not consistent regarding the A/C. It turns from cold to EXTREEMLY hot, just by it self, while driving on a speed above 50 mps. If I turn it off for few minutes and then turn it on it will go back to cold but after a while it heats up again. Does anyone experience the same thing? Any idea what could be the reason for that?
Ther R143 refridgerant over time breaks down into water itself - so over time the existing R134 refridgerant gets less effective, and ultimately you will experience these types of symptoms.
The most often successful fix to for a proper refridgerant re-charge - and the machine sucks out the old refridgerant - holds a vacuum for 2-5 min to check for any leaks - and if no leaks detected on holding the vacuum, pumps in a full recharge with fresh refridgerant.
The ML aircon is not any mystery at all, and operates like all other R143 systems, so any indie offering a good deal on the process will work out for you, normally from $50-$80 for the service.
A DIY top-off with a auto parts store can of R134 might help for a little while, but a full evac-refill is the solid fix.
Fluctuating cold and extremely hot air seems like malfunctioning air mixture flap (air mix damper door). It sits on top of the A/C system (behind the radio) and regulates the temperature of the airflow. Do a search and you will find the instructions.
Thank you fabbrisd1 for your explanation. Actually, I live in Southern California, and sometimes I use the A/C during the day in winter. I thought it is an ML problem, like all the other issues in the MLs. I am just surprised because I can feel the A/C switch moving to extreem heat. Even if I switch off the A/C it still keeps getting exteemly hot air that will be even too hot in very cold states. I have a feeling it is something related to a sensor or something. Please advice.
Thank you fabbrisd1 for your explanation. Actually, I live in Southern California, and sometimes I use the A/C during the day in winter. I thought it is an ML problem, like all the other issues in the MLs. I am just surprised because I can feel the A/C switch moving to extreem heat. Even if I switch off the A/C it still keeps getting exteemly hot air that will be even too hot in very cold states. I have a feeling it is something related to a sensor or something. Please advice.
Like Merzatt has previously said, whenever you have uncontrolled temperature swings in the A/C/Heater system it is almost always due to a problem with BLEND DOOR Actuator Motor. You can visually check its' operation, at least to some extent, by removing the radio/MCS unit and then center section of the dash (wood trim panel which holds the climate control unit)............see pdf #1. Note: BEFORE REMOVING THE RADIO/MCS UNIT, BE SURE YOU HAVE THE PROPER RADIO CODE FOR REINSTALLATION.
After removing the above, you will see a flat object, (Actuator Motor) similar to the size of a pack of cigarettes, ..........see pdf #2.........With the plugs attached to the Climate Control, place your settings for A/C, and start up the truck. Then place your hand on top of the actuator motor, and with one of your fingers feel for a small indentation, off to the left of the actuator motor, see arrow on pdf #3. Then place your settings for heat. After about 5 seconds if you do not feel the indentation revolving, then the actuator motor is faulty and needs to be replaced. Replacing the actuator motor is a difficult task but it can be done without removing the instrument panel. Post back with your results or if you need any further help.
good luck with that one, I had the same exact problem on my '98. It was the flapper box and it cost me like $1200 to have it repaired. The part is pretty expensive and they have to take the whole dash out to get to it.
ML320 1998 A/C Problem
Linear Mode
