Ticking sound

[sdpartz]

I have a 98 ML320 with 190K miles she's been a great truck but has now a ticking sound coming from somewhere at dash behind the radio, it starts when I turn on the ignition. it seems to be a relay and continues on, I hope it's not a ticking time bomb

[mercman163]

HAHA no not a time bomb, but that was the first thought in my mind, (did I not pay some one? lol) Anyways. My ML has been doing that for almost a year now, and I think I know what it is. I also have a 98 ML with 204K. What I think is the problem is the climate temp control is going bad. through the summer it was fine, except the ticking sound. During the winter it seems to be stuck on a certain temp on the warm side. when I move it to the cooler side it wont change temp just tick. But I have found where the clicking stops is on a certain setting on the thermostat in the red where I had it one day now will not come out of it. I'm still trying to research on how to remove the center dash part to examine it.

[dieselken]

My 99 ML is doing the same thing. I was told that that air blend motor is going bad. Apparently it's a big job to replace this part as the entire front upper dash needs to be removed to get to it.

[mbdoc]

Blend air flap motor can make that type of noise.

Takes about 6-7 hrs to replace unless you have small hands & can replace motor w/o removing the dash thru the glove box area.