Battery Light when AC was on.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 56
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From: San Diego
C240
Battery Light when AC was on.
Hey guys! Wanted to get some input on what could be the possible problem with whats been going on. Last friday my 02' C240's Battery warning came on. I just had left the store and the car baked in the sun so it was pretty hot inside. I don't usually use the AC at all and just drive with the front windows down unless I have passengers because I usually just deal with the heat.. But maaan, it has been pretty hot in Socal lately so I had to turn it on. I used the AUTO AC so I could flush out all the hot air until bearable enough for my to turn off and just roll with the windows down. I noticed after coming from a full stop the car was feeling kind of sluggish.. I looked at the cluster and noticed the battery light was on, also at the time I had the radio on too. So I decided to turn both the AC/Radio off and the battery warning went away. Car drove fine the rest of the way home. The same day I was driving with passengers so I decided to turn on the AC, but used manual mode. I noticed when the AC speed is above 3 the car feels kind of sluggish after coming from a full stop, but no battery warning.
The battery has been changed within this last year so it's a few months old. Also the alternator has been replaced just about two years ago, but I'm still leaning towards it being an alternator issue.. I'll have my cousin check out the battery voltage and see if maybe it's the voltage regulator that needs to be replaced. So let me know if you guys know if there could be any other possible reason to why I'm having this issue. I'll update you guys when I get the battery voltage checked out possibly tomorrow or Tuesday since I'm off that day and see if it's the regulator.
Thanks in advance!
The battery has been changed within this last year so it's a few months old. Also the alternator has been replaced just about two years ago, but I'm still leaning towards it being an alternator issue.. I'll have my cousin check out the battery voltage and see if maybe it's the voltage regulator that needs to be replaced. So let me know if you guys know if there could be any other possible reason to why I'm having this issue. I'll update you guys when I get the battery voltage checked out possibly tomorrow or Tuesday since I'm off that day and see if it's the regulator.
Thanks in advance!
Last edited by FreshVibes; Sep 8, 2013 at 11:20 PM.
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From: 1 hours drive north of Sydney Australia
2007 W204 220CDI Classic Sedan
I wonder whether the A/C load is higher than it should be (eg bearings /vanes seizing) so when the engine is at idle & the RPM is reduced causing low output from the alternator.
Would be interesting to see what occurs when turning the A/C on & off when the engine is at operating temp & at idle. Do it over a minute or two as it takes a while for the vanes to open & close.
Would be interesting to see what occurs when turning the A/C on & off when the engine is at operating temp & at idle. Do it over a minute or two as it takes a while for the vanes to open & close.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 56
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From: San Diego
C240
I wonder whether the A/C load is higher than it should be (eg bearings /vanes seizing) so when the engine is at idle & the RPM is reduced causing low output from the alternator.
Would be interesting to see what occurs when turning the A/C on & off when the engine is at operating temp & at idle. Do it over a minute or two as it takes a while for the vanes to open & close.
Would be interesting to see what occurs when turning the A/C on & off when the engine is at operating temp & at idle. Do it over a minute or two as it takes a while for the vanes to open & close.
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From: 1 hours drive north of Sydney Australia
2007 W204 220CDI Classic Sedan
I would have thought we would be looking for the symptoms your describe. ie battery light coming on & abnormally low engine idle speed.
Thread Starter
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From: San Diego
C240
Oooh, alrighty. Well, I did test it today right before I got to work. Before exiting the freeway, turned on auto AC, NO battery warning, but car was sluggish after coming from a full stop.
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From: 1 hours drive north of Sydney Australia
2007 W204 220CDI Classic Sedan
Fresh Vibes,
Could you explain in more detail what you mean by 'the car was sluggish after coming from a full stop' ?
Do you mean that it is idling roughly when stopped or sluggish when taking off from stopping ?
Interested to hear what your cousin comes up with on Tuesday.
Could you explain in more detail what you mean by 'the car was sluggish after coming from a full stop' ?
Do you mean that it is idling roughly when stopped or sluggish when taking off from stopping ?
Interested to hear what your cousin comes up with on Tuesday.
Thread Starter
Junior Member
Joined: Feb 2012
Posts: 56
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From: San Diego
C240
Fresh Vibes,
Could you explain in more detail what you mean by 'the car was sluggish after coming from a full stop' ?
Do you mean that it is idling roughly when stopped or sluggish when taking off from stopping ?
Interested to hear what your cousin comes up with on Tuesday.
Could you explain in more detail what you mean by 'the car was sluggish after coming from a full stop' ?
Do you mean that it is idling roughly when stopped or sluggish when taking off from stopping ?
Interested to hear what your cousin comes up with on Tuesday.
Last edited by FreshVibes; Sep 10, 2013 at 12:53 AM.
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Thread Starter
Junior Member
Joined: Feb 2012
Posts: 56
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From: San Diego
C240
Car is totally fine with AC off. Car is sluggish when using AUTO A/C. If I use the manual A/C and the speed is above 3, the car is sluggish. 
And will be going over to my cousins to check out the output tomorrow and anything else that could be causing the problem.
And will be going over to my cousins to check out the output tomorrow and anything else that could be causing the problem.
MBWorld Fanatic!
Joined: Mar 2008
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From: 1 hours drive north of Sydney Australia
2007 W204 220CDI Classic Sedan
1. A/C compressor is seizing when in service causing heavy load on auxiliary belt & causing car to be sluggish. .
2.Air conditioning system when is service has a abnormally high electrical load causing the cars system voltage to fall below normal levels ie high belt load on A/C & also on alternator..Any belt squeal /slippage?.See if your cousin can have a system voltage reading when the problem is occurring
3. The A/C /engine management system may be faulty . Ie the one that adjusts the engine speed when the A/C is on. Do you have any fault codes showing up.
Interested to know how you go.
John
Thread Starter
Junior Member
Joined: Feb 2012
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From: San Diego
C240
To my way of thinking it can be one of three things :-
1. A/C compressor is seizing when in service causing heavy load on auxiliary belt & causing car to be sluggish. .
2.Air conditioning system when is service has a abnormally high electrical load causing the cars system voltage to fall below normal levels ie high belt load on A/C & also on alternator..Any belt squeal /slippage?.See if your cousin can have a system voltage reading when the problem is occurring
3. The A/C /engine management system may be faulty . Ie the one that adjusts the engine speed when the A/C is on. Do you have any fault codes showing up.
Interested to know how you go.
John
1. A/C compressor is seizing when in service causing heavy load on auxiliary belt & causing car to be sluggish. .
2.Air conditioning system when is service has a abnormally high electrical load causing the cars system voltage to fall below normal levels ie high belt load on A/C & also on alternator..Any belt squeal /slippage?.See if your cousin can have a system voltage reading when the problem is occurring
3. The A/C /engine management system may be faulty . Ie the one that adjusts the engine speed when the A/C is on. Do you have any fault codes showing up.
Interested to know how you go.
John
The AC compressor seizing was one of the things my cousin pointed out first other than the alternator. We'll be looking at the car today once he gets home. I'll let you know what we look at and find out!
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Joined: Sep 2006
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From: FLORIDA
2003 C240
In the past, I get undevoltage error everytime I use the 'AUTO' mode. I checked the battery as well but it was not the source of the problem. I replaced the HVAC module and never had a problem since.
Good luck.
Good luck.
