Need help - AC dragging Engine performance hugely
 

The car is 2014 Mercedes E550 Sedan
I have been hunting the source of this issue for couple months already.
It started last year.

Whenever AC is on (Or hot air is on), engine performs poorly.
At least 25-30% power gone.
Car sounds loud and heavy.
IAT also up 10c
It still makes cold air.

At first, i thought its AC compressor or AC clutch issue.
So, went to a Shop, replaced AC compressor.
Shop also check on freon leak, no leak neither.


hoping to get some recommendations where to go

Any help is appreciated

What car?

The car is 2014 Mercedes E550 Sedan

Have you scanned for codes with a device capable of viewing manufacturer specific dtc's?

I have got Mercedes Benz Dealer Star Diagnostic system. (Xentry)
It didn't show any code or error.

Very strange.

The next thing i am going to check is Alternator.

When I have AC on, feels like my car loses 100hp (1/2 my car HP) LOL =P

Which means you might have same problem too. lol

I don't know how the really new stuff works but my guess would be the idle air system isn't adjusting for the A/C being on? What happens at idle if you switch it on?

rev up your engines!



sorry i'm of no help, hope it gets fixed

engine running hot? radiator not working properly?

Switch AC on at idle, engine sound changes. The sound goes deeper. And it sounds more like room room room...
I will check on idle air system that you mentioned tomorrow.

LOL....I did go through some of his videos looking for clues!!

Engine temp is around 97-104c most the time.
It doesn't get change after AC turned on.

You mentioned Radiator!! IAT goes up around 10c !!! (ambient temp 30c, with AC on, IAT goes up to 53c)

What happens to the rpm? up/down/the same?

Try having an EG Civic and turning the AC on lol

You have to slip the clutch, off the line, or it'll stall :lol

Did you say hot air also does this somehow?

Makes me think it may have to do the electronics in climate control.

What happens when you try to change the temperature?

Have you looked for any possible service bulletins/ TSBs?
It might be a silly reprogram or something. It's possible with these late model cars....

In my Integra, i have to shut off the A/C when i'm going uphill lmao. The other time when 2nd Narrows was shut down and i detoured thru Downtown for 2 hours in the blazing heat w/ A/C on, i lost at least a quarter tank of fuel... normal for old cars

Heat from A/C condensor is effecting your IAT temps. higher IAT temps means less dense air; less dense air means less oxygen to fuel combustion.
That combined which energy loss from running a/c compressor you get quite of bit of energy loss. Seems normal to me.

RPM doesn't change much at idle. Its always at 610-620 at idle.
But car does rev higher to shift to next gear.

As soon as i turn on AC (Or Heater), the whole issue starts.
Just tried today, changing temperature doesn't affect anything.

I have checked with Mercedes, nothing new or update for AC since 2015.
I might change different tune. See if anything changes.

Thats exactly car shop tech told me.
I totally understand it. and agree to it.

But, I didn't feel this much of power lost or engine running rough 18 months ago.

But isn't it kinda weird how the heater is also impacting his performance? If you have A/C off but you are blowing hot air, it shouldn't slow the car down. In fact, cabin heater works as a small radiator for the engine, which helps with engine cooling.

^depends on the brand, some manufactures will run the compressor when the defrost is on to dry out the air in the cabin

^this. Vehicles with automatic climate controls will use a/c without you actually turning it on.
For a quick test, manually put a/c in "off" mode with HVAC still running and see if your car still has loss of power then.

Just having HVAC on (AC off).
Car runs normal.

That's the reason I thought ac compressor or AC clutch is not running smoothly.
So, I replaced ac compressor with clutch.

But issue still there.


so....
- Just having HVAC running (AC off), car runs fine.
- AC (or Heater) on, at idle Engine load goes from 11% to 16%
- AC Compressor / Clutch also just got replaced. Which means, problem is not on the Compressor.

Problem is not on Compressor, or Compressor Clutch.
What else would cause this issue when AC on ??

^mode selector isn't set to defrost when you tested right?

defrost is always off when i did the test.

can you check how much amperage increase when the AC comes online?

its one of the settings when u access the maintenance reset menu in your odometer

This thread reminds me of turning the AC off in my old EL to get up Royal Oak a bit easier LUL :okay: