okay...i start my ml...never shift out of park. i turn on the ac, and there is a slight "click" noise... and the rpm's rise slightly to a little over 500 rpm. it repeats the process every once in a while... "click", "vroom", "click", "vroom"... not really loud, but definitely audible. i dont think it was there before. people are telling me that its normal cause i didnt move the car when the ac was on, and cause its so hot here. any ideas? should i be worried. (and i just got my ac fixed a few days ago).

 

so this is when the car is at rest? I am assuming this is your 2000 ML, I believe it is normal. The clicking is probably the A/C compressor engaging, the vroom could be the AUX fans engaging to cool the A/C condensor infront of your radiator or it could be the engine idle raising slightly to compensate for the load caused by the compressor. I notice my ML will sometimes shudder a little bit (very minor) at idle and it has done this ever since i can remember. Remember, cars are a machine, u can only insulate the noises so much.

BTW, my old Lexus (supposed to be known for ultra quiet and smooth vehicles) had a constant "water flowing" noise behind the dash board and a hissing noise whenever the A/C was on. Also on the highway if you engaged the A/C you could feel the whole engine shake on its engine mounts, none of my mercedes do that nor does the BMW. But that damn A/C was one of the most powerful units I have ever experienced in any car..... that was probably one of its best features .

 

Thanks AlBoston, it is for my 2000. im not worried about noises, im just worried about it being a problem. but you made me feel a little better, thanks/

 

Hey guys, mine does the same. I understand it to be the engine increasing the rpm to compensate for the load. The same thing will happen if you put other loads on the engine when at park, ie turning the steering wheel whilst at a standstill will make the engine pick up slightly.
To help out the a/c unit, allow the engine to warm up first, put the fan on without the a/c, and when you put the a/c on, press the air-recircular, so the unit cools cool air and not hot air from outside the cab.

Hope it helps

nick.

 

thanks Nick.

 

The tips from Al and Nick are correct. One thing that bothers me though: you mention that you've never heard this b4. Usually the person who drives the vehicle most knows when unusual noises creep up. Though this sounds normal, do you recall trying this in idle b4 the system was fixed. One way to find out is to go to your dealer and ask for a test drive of a similar vehicle. If they have your year ML, that's even better. Then you'll know with better certainty what the noise is all about. I know that my 320's condenser fan cycles a lot at idle causing higher than idle RPM. It's normal for the small engine to do that. It should be much less noticeable with the V8 though. As a matter of fact (and I'll have to check this), when the compressor comes on with the bigger engine, the RPM drops a bit ('cause power is being sucked out), then the computer kicks in to get the idle RPM back to normal. In my Z, the idle-up solenoid handles this function, thereby maintaining an almost constant RPM when load is applied at idle - lights, etc.

One thing I noticed on my Z: when the drivebelts are not properly tensioned, the idle solenoid allows a somewhat higher than normal RPM, with more noise. However, we're talking about a 14yr old vehicle, but it could just be a clue. Lots for you to think about.

Are you out of warranty now? Did they get all that pre warranty stuff taken care of?

 

whats up Darkmann...thanks for the post, definitely food for thought. its strange that ive never noticed it before, and im pretty sensitive about my car. i think the most concerning part of everything is the "click" noise i heard... but i have not felt any ill effects since, so i am hoping that everything is okay.

you have a good memory, i just ran out of warranty on Tuesday. oh well, looks like no more freebies. and the dealer took care of everything for me. nav is on point now. no more torsion bar noise. tranny shift is supposedly normal, and radio no longer pops. actually the dealer even found a bunch of additional stuff wrong and took care of it for me. leak in the differential, power steeriung leak, ac partial failure, and a couple of other things.

hey, i didnt know you got the Z?!? last time we talked you were waiting for some extra garage space. lucky bas.... how is it... remember i wanted one too?