W212 HIGH IDLE WHEN HEATER IS ON

Quaver

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hi guys
So I have been having an issue with the car idling high when the heater is on but as soon as I turn the heaters off it goes straight back to normal idling. Once fully warmed up then it's fine again but EML is lit. I did a diagnostic and The fault showing says "the power supply is too low. The signal amplitude is less than the minimum amplitude"
 
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Battery? Idling up would be auto response to a major current draw if the battery is low. Fault code also seems to indicate that.

Ian.
I did think it was the battery or regulator but just wanted to make sure. Thanks
 
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does anyone know which battery spec i need to get and which brand is best recommended please?
 

John Laidlaw

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You’ll get a great deal on an MB Battery and get the right one from MB Grangemouth- they just need your Reg or vin 01324 682002 quote MBO for discount...and you’ll get a nice free MB fleece blanket too at the moment !
See the ad in members area
Edit : I’ve always used telephone number 01324 686002 - I see their ad has 682002 might be a typo or alternate number
 
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umblecumbuz

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Faster idling is also a side effect of turning on air conditioning, so there could be a possible glitch in the relationship here.
 
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Faster idling is also a side effect of turning on air conditioning, so there could be a possible glitch in the relationship here.
So what could be the possible cause of this?
 

John Laidlaw

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Bad idle control valve or controller possibly. Battery change was likely necessary anyway so a good start. Don’t run ahead just yet!
 

malcolm210

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It wouldn’t surprise me if the high idle is a result of low battery voltage I would certainly change the battery first without digging any further, that is if the battery is low voltage and has a problem
 
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It looks like it's the original battery and the car has done 82000 miles so I think it is most likely the culprit. Will get it changed and see what happens
 
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Hi guys so I just need some advice on the battery I need. I have attached the one I currently have fitted and need to know if it's AGM or standard?? And is it ok to use a AGM 1? Thanks
 

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malcolm210

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Varta are excellent just talk to your local batter supplier or MB may offer you a good deal
 

John Laidlaw

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That’s an AGM battery, Grangemouth will give you a good deal, honest! Or go to Tayna. Halfords and ECP are expensive - haven’t tried kwik fit recently
 

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I don't know why NO ONE is listening....


under the sticker of your AGM battery is 6 screw top lids.... unscrew and put 50ml of distilled water in each of the battery cells, put on charge for 24 hrs it will work good as new for another 5 years !!!!
 
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That’s an AGM battery, Grangemouth will give you a good deal, honest! Or go to Tayna. Halfords and ECP are expensive - haven’t tried kwik fit recently
Grangemouth is a bit way out for me and need it asap as going on a road trip soon so just got a Bosch 1 from ECP for 198£
 

John Laidlaw

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I don't know why NO ONE is listening....


under the sticker of your AGM battery is 6 screw top lids.... unscrew and put 50ml of distilled water in each of the battery cells, put on charge for 24 hrs it will work good as new for another 5 years !!!!
Is that the sticker and caps which are vented and say ‘do not remove ‘ on them? AGM’s I understand don’t lose water so....
If you don’t get an additional quantity just right might you not have the joy of nicely watered down corrosive sulphuric acid flowing onto your battery tray? Interested as I love to save money like anyone else....
 

John Laidlaw

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Wow. Thought batteries were dear here in Oz. That is waaay out there. We pay about AU$160 for a similar battery here, which equates to about 100 pounds UK.

Ian.
Yip Ian a real rip off
Probably the cheapest if he shopped around maybe £120 for the same spec
 

John Laidlaw

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Grangemouth is a bit way out for me and need it asap as going on a road trip soon so just got a Bosch 1 from ECP for 198£
They ship to you next day for £5 but glad you got it sorted
 

Botus

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Is that the sticker and caps which are vented and say ‘do not remove ‘ on them? AGM’s I understand don’t lose water so....
If you don’t get an additional quantity just right might you not have the joy of nicely watered down corrosive sulphuric acid flowing onto your battery tray? Interested as I love to save money like anyone else....


there is NO indication on the battery to tell you not to do this on my genuine merc AGM battery, you are worrying over NOTHING. they ONLY want you to buy a battery, there will be no acid going anywhere. It will be dry as a bone 50ml will just vanish, tip it upside down NOTHING will come out
 

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