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I noticed when my AC is on I get a higher idle and at a standstill the tachometer shows about 4 tics higher then it would without the AC on. Also I feel a bit of a pull-forward sensation. Anyone else experiencing this?
computer adjust idle to handle the extra pull of the air compressor when the AC is on . This is pretty standard. I have a ML350 and have not noticed this but will see if mine is doing this. I know in my other i.e. older cars it worked that way.
4 'tics' being about 400 rpm ? It goes from what ? 600 to 1000 ? Sounds a bit high, would've expected more like 850-900 but yeah, when the AC clutch engages the rpm goes up.
4 'tics' being about 400 rpm ? It goes from what ? 600 to 1000 ? Sounds a bit high, would've expected more like 850-900 but yeah, when the AC clutch engages the rpm goes up.
I believe it is between 800-900 at a standstill, at a light with AC on. When I turn off the AC it comes down to 400-500.
I agree with the ~500 rpm with AC on, but no pull forward sensation when it's kicked in (GLS450).
Here a snap with the AC off at a stoplight.
Your vehicle should be running, at a stop light or position with the AC on. What is your rpm and when you lift your foot off the brake is there a pull forward sensation?
I was away for a few weeks and just before leaving I went for a ride and noticed the experience I had went away. When driving with the AC on and coming to a stopped position my RPM's were now consistently at 500 RPM. After driving around a bit I noticed a climb back to 800-900 at a standstill with the AC on. I will visit the dealer but I'm trying to see if there's some trigger I'm overlooking and also if any of you are experiencing the same thing.
Last edited by jerome8283; Aug 6, 2017 at 09:57 AM.
I have the same problem new gls450 when outside temp is over 90 deg dealer says this is normal after keeping it for a week to evaluate. I don’t believe them.
I have the same problem new gls450 when outside temp is over 90 deg dealer says this is normal after keeping it for a week to evaluate. I don’t believe them.
Finally someone else with the same problem. If this were normal others would have the same experience. So far it's you and I only on this forum. I still have the problem!
Last edited by jerome8283; Jul 6, 2018 at 03:33 PM.
I have contacted a friend of mine who works at MB credit Corp she is going to talk to some people in the complaint department I’m getting no where with the dealership I’ll let you know how I make out I believe it’s a faltiy isle control valve
I have contacted a friend of mine who works at MB credit Corp she is going to talk to some people in the complaint department I’m getting no where with the dealership I’ll let you know how I make out I believe it’s a faltiy isle control valve
Great! I'd love to resolve this. Thanks for sharing!
I noticed when my AC is on I get a higher idle and at a standstill the tachometer shows about 4 tics higher then it would without the AC on. Also I feel a bit of a pull-forward sensation. Anyone else experiencing this?
Has anyone taken this problem to the dealer I have twice after keeping it for a week they said it is normal I don’t believe them.
Seems to me that this is intentional because it only happens when the temperature goes into the 90's. I guess the A/C compressor needs a more little power/higher rpm's to keep up.
And obviously the higher the rpm's, the more the engine pulls, so you have to break harder to keep the car from moving. Good thing we have the hold feature!
Seems to me that this is intentional because it only happens when the temperature goes into the 90's. I guess the A/C compressor needs a more little power/higher rpm's to keep up.
And obviously the higher the rpm's, the more the engine pulls, so you have to break harder to keep the car from moving. Good thing we have the hold feature!
The compressor does need a decent amount of RPM to work properly, at 5-600 rpm the compressor can barely keep up with a big vehicle on a hot day. The AAC has authority to increase idle speed for better cooling power. I'd have to compare it to another vehicle, but it sounds very normal.
Seems to me that this is intentional because it only happens when the temperature goes into the 90's. I guess the A/C compressor needs a more little power/higher rpm's to keep up.
And obviously the higher the rpm's, the more the engine pulls, so you have to break harder to keep the car from moving. Good thing we have the hold feature!
I have never experienced this with any of the many vehicles I've owned. I will take pics and post them as soon as I have an opportunity. My wife doesn't notice it but I do.
Also, it doesn't seem that many here have experienced this.
While I don't have a GLS (yet), my E350 idles around 500rpm most of the time, on hot days with AC on it'll go up to around 800rpm. My wife's BMW X3 with it's little 4 cylinder idles around 800 rpm normally, on hot day with AC it'll sometimes go as high as 1100 to 1200 rpm at idle.
Having to idle a little higher with AC running on a hot day is pretty normal.
Seems perfectly normal for the V6. A vehicle with such a myriad of electronics on a hot day will tax the v6. The fact is the v6 is adequate for the GLS but the turbos that make that possible are not a factor at idle.
Ok here are some pics when the AC is on and off. Both times the car is in drive, at a stopped position, at a stop sign. Also note the temperature is 77 degrees.
AC-ON
AC-OFF
Last edited by jerome8283; Jul 12, 2018 at 11:37 PM.
I'm just wondering based on my pics if others are seeing the same thing? Is this related to the 450 only?
I could have taken the exact same photos today in mine, it was 82 degrees outside. At first the engine idled as usual and at some point the rpm's went up. When I turn the A/C off it goes back to 500 rpm's. Don't forget the A/C doesn't just regulate the temperature, it handles the humidity as well. I think it's normal. I remember when engines always used to idle at 800 - 900 rpm's and I did not have A/C back then.
Just a possibility : It might not be the aircond compressor alone raising the idle speed, it could also be aircond compressor + alternator demand at that point in time that idle get raised to 800-900 RPM.
The electric cooling fan is a big one and heavy on the electrical consumption. Newer cars have data link to alternator voltage regulator called BSS or LIN, and intelligent battery sensor, it could sense insufficient amperage at 500 RPM and trigger idle speed increase.... maybe.
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