Battery issues? Hopefully not Alternator or Voltage regulator.

Chirag

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Hi Helpful Merc people.



Just a question!



My Merc = 05 Plate CLK 270 cdi in Black. Currently 225k (largely trouble free motoring too!).



I currently have a Halfords battery with 3 year guarantee that has been in the car for 4.5 years (put in by the previous and 2nd owner). This morning after 1 days inactivity, the car has had trouble starting and I got it going on 4th crank with my foot on the accelerator.



It usually starts first time as I have a 25 mile (each way) commute for work and gets a good charge.



A quick reading I got from the dash whilst I attempted one of the starts was 12.1v



As I got the car out the garage the steering was very stiff (was fine once I got moving). A red light then came up in the middle of the dash saying “Visit Workshop” with the battery symbol.



After a 25 mile drive the warning light has now gone and readings are as follows:



Battery prior to start 12.6v

On Start (idle) 13.9-14.1v



Any advice on whether this is as it seems just a new battery issue, or anything more sinister such as the alternator (good grief!). I don’t want to put stress on the alternator of an old-ish car so happy to get a decent battery.



Any advice on the battery to go for on these cars? – Halfords worked fine, so I’m guessing Bosch would be a good shout?

Thanks!
 

M80

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Charge voltage of 14.1v is a little low but your alternator is charging.

Battery at 12.6 prior to start is good enough. But that doesn't guarantee battery capacity and therefor capability. But I wouldn't be thinking that is showing a bad battery.

12.1v during a start is good, I would say that shows a healthy battery.

The battery symbol is likely showing the battery voltage had fallen during a long start, but it recovered.

I would monitor for a few days before assuming the battery is the problem. It is possible you have some air that's ingressed into the fuel line/s. Not uncommon on your earlier engine at this time of year.
 
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AMGeed

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^ In addition to above, get the battery load tested to see if reaches its CCA.
Halfords offer this service but you don't have to buy another battery there.
Main dealer and ECP with one of thier non stop sales can beat Halfords price.
 
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Chirag

Chirag

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Charge voltage of 14.1v is a little low but your alternator is charging.

Battery at 12.6 prior to start is good enough. But that doesn't guarantee battery capacity and therefor capability. But I wouldn't be thinking that is showing a bad battery.

12.1v during a start is good, I would say that shows a healthy battery.

The battery symbol is likely showing the battery voltage had fallen during a long start, but it recovered.

I would monitor for a few days before assuming the battery is the problem. It is possible you have some air that's ingressed into the fuel line/s. Not uncommon on your earlier engine at this time of year.

Thanks Martin – much appreciated. I think you may be correct and I’ll keep monitoring.



Went out for ~7 miles at lunch. Started right away - dash showed 12.4v on start-up and 14.8-14.7v on driving and finally settling to 14.4v



Interested to know the workings of how air would get into the fuel line.

The car is used daily and left in the garage most weekends. It wasn’t used yesterday on quite a cold day.
 
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Chirag

Chirag

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^ In addition to above, get the battery load tested to see if reaches its CCA.
Halfords offer this service but you don't have to buy another battery there.
Main dealer and ECP with one of thier non stop sales can beat Halfords price.

Thanks. ECP was first on my list.

Any thoughts on when to replace a battery? Its always seemed a bit Russian roulette to me, I’ve ussually had trouble starting before the slippery slope of needing a jump etc on previous cars. The battery is now 4.5 years old and was guaranteed for 3 years.

I'm surely on borrowed time. I'm also worried about compromising the alternator just for a few weeks of extra use of an old battery.
 

M80

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I'm assuming being the 2.7 that you have the opaque fuel lines, these have 'o' rings where they push in to the connectors.
The 'o' rings harden and flatten over time, and allow air to pass.

Often after the engine has just started you can see air bubbles within.

There are 6 or 7 'o' rings, at about 20p each.
The trickey bit is getting to them w/o breaking the older brittle plastic.
Pre warming the engine bay can help there.
 
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Chirag

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I'm assuming being the 2.7 that you have the opaque fuel lines, these have 'o' rings where they push in to the connectors.
The 'o' rings harden and flatten over time, and allow air to pass.

Often after the engine has just started you can see air bubbles within.

There are 6 or 7 'o' rings, at about 20p each.
The trickey bit is getting to them w/o breaking the older brittle plastic.
Pre warming the engine bay can help there.

Thanks Martin, yes, opaque fuel lines indeed. Thanks for the info!
 

M80

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Jeep Grand Cherokee 2.7CRD Mercedes ML270 Fuel Line O Ring Seals x 8 GREEN VITON | eBay

a bit more pricey than I remember, it should still be an economically viable repair though.

Wrapping some self amalgamating tape around the connectors can be a fix, but maybe not as reliable to get a sure seal w/o using a fair amount of wrapping, and not as pretty. It can save breaking the connectors though.
But being self amalg' it needs to be warmed some. I'm never happy with insulating tape and the cr*ppy look and yuk left when removed.
 

kid-jensen

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The "heavy steering" is a clue as to what's going on...

I reckon you have a slipping belt.. There may be nothing else wrong as all (If you're lucky)
 

alexanderfoti

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The "heavy steering" is a clue as to what's going on...

I reckon you have a slipping belt.. There may be nothing else wrong as all (If you're lucky)

Yes, quite possibly from leaking diesel around the LP pump due to seals.
 

M80

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If the belt has been slipping enough to discharge the battery while driving wouldn't there be an alternator warning on the dash?

There may even be heavier steering experienced at other times.

I was ignoring that as being a seperate issue, thinking a steering fluid change might be good in future.

Of course it's worth looking for the leaking diesel, the smell under the bonnet might give that away.
 

alexanderfoti

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If the belt has been slipping enough to discharge the battery while driving wouldn't there be an alternator warning on the dash?

There may even be heavier steering experienced at other times.

I was ignoring that as being a seperate issue, thinking a steering fluid change might be good in future.

Of course it's worth looking for the leaking diesel, the smell under the bonnet might give that away.

Yes but the battery warning in red is the alternator warning.
 
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Chirag

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Thanks for the updates all.

As per my reply to Martin, kept it monitored the last few days.

-I have disconnected my dashcam

-been driving without the Command on

-Lights used on way home but i always use these manually as opposed to having them on via sensor.

Car has started without any issue or any warning light (this is at lunchtime and on my way home).

Overnight - its coughed a couple of times before starting each morning but not as bad as on Wednesday morning (when this all kicked off).

Steering has been ok. Output on the dash tells me the voltage is ~12.3v on overnight start prior to turning over. Once started the alternator kicks in and its at 14.1-14.5v for the journey.

I am wandering whether (after watching a Kent video) its my battery not having the CCA it once did?

I'm due an A service in 1k miles and the car is in at my Merc Indie in late February, I will get the alternator belt checked out - or is this something more urgent?

Edit - I forgot to mention that there is a brief buzzing noise when i finish my journey and take the keys out of the ignition, I've always thought that this was the alternator finishing 'doing its thing'. Not sure if its a concern.

Thanks all for your updates.
 

alexanderfoti

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Thanks for the updates all.

As per my reply to Martin, kept it monitored the last few days.

-I have disconnected my dashcam

-been driving without the Command on

-Lights used on way home but i always use these manually as opposed to having them on via sensor.

Car has started without any issue or any warning light (this is at lunchtime and on my way home).

Overnight - its coughed a couple of times before starting each morning but not as bad as on Wednesday morning (when this all kicked off).

Steering has been ok. Output on the dash tells me the voltage is ~12.3v on overnight start prior to turning over. Once started the alternator kicks in and its at 14.1-14.5v for the journey.

I am wandering whether (after watching a Kent video) its my battery not having the CCA it once did?

I'm due an A service in 1k miles and the car is in at my Merc Indie in late February, I will get the alternator belt checked out - or is this something more urgent?

Edit - I forgot to mention that there is a brief buzzing noise when i finish my journey and take the keys out of the ignition, I've always thought that this was the alternator finishing 'doing its thing'. Not sure if its a concern.

Thanks all for your updates.

No worries about the buzzing. It's the vac transducer and normal.
 

M80

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Your buzzing is possibly the SAM / ECU cooling fan. It's not essentiloa, especially in winter. But may be worth a look over / clean.
There is a small fan behind the dash also. You should see the vent above your left knee.

You should be able to check your aux belt reasonably easily. The suggestion is that it is diesel saturated and slipping. You should be able to see / smell evidence.
More important to me is looking at the inside of the belt, the multi ribs, for evidence of cracking and therefor possible failure. A good look with a torch at the inside as it passes over a pulley would do for that.
 

LostKiwi

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12.3v is too low and suggests a poorly battery.
The rule of thumb is 12.6v is a good battery, 12.4v is near end of life after 12 hours of no use.
 
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Chirag

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Hi All,



Thanks for everyone’s help and advice. I ended up taking the plunge and getting a new battery. As explained before, the alternator goes from 14.1 – 14.8 when driving but the battery was at 12.3v max in the mornings. I’ve had the same 3yr Halfords battery since buying the car from the last owner 5 years and 60k miles ago.



I ended up getting a S4 Bosch 4 year with 95ah and 800cca. It was from the ECP online ebay subsidiary which ended up costing £97 with a discount code. I received the battery yesterday and also fitted it with the help of a work colleague as he drives around with a rather handy spanner set!



Fitting



I’ve seen so many posts about this – so I thought I’d give my experience and hope it helps someone. I had heard about donor batteries etc and chargers etc, however, I went for the straight swap approach. Tools needed – new battery + #10 socket and wrench.



  • Car was locked and windows up as advised.
  • Bonnet into maintenance mode with the red button.
  • Cabin air filter unlatched
  • Battery wouldn’t move and then saw the bracket holding it in place on the LHS – this is where the #10 socket came in.
  • Finger loosened the nuts the rest of the way – being careful not to drop them.
  • Battery cables negative and then positive undone
  • Alarm goes off! I am not sure if I should have turned this off right at the start, however on unlocking the car and turning alarm off, and trying it again, the alarm sounded again.
  • Unlocked car and pulled out old Halfords battery – this had a little straw pipe attached to it (not sure what this does and if I need the equivalent on my new set-up). No Alarm sounding off.
  • Put the Bosch battery in – very flush fitting and need to be wary of cables, this is where a 2nd person pushing them away was handy.
  • Connected positive and negative cables.
  • Started car - first time start
  • Tucked cables down
  • Forgot about the bracket that was initially undone, so battery back out and bracket back in and finally re-attached battery.
  • Clipped the cabin air filter back on.


I saw that the battery had “min 12.4v” on the side, assumed this meant it came charged. I left the car at work from around 13:30 till 18:00 and it wouldn’t start on my way home. I got it going on 3rd attempt after a bit of accelerator down. Could it be that the battery has sat for a bit and needs a charge?

I noted that the drivers side windows didnt come up as i sat in the car, and so did the reset of 'down and then up, holding up for 5 secs' this worked.


On the drive home, I had the “secret menu” going, as I have been monitoring it the last few days. The battery prior to start showed 12.4v and all the way home the alternator was 14.5 (reaching 14.8 for a moment), barring the stops at the traffic lights where it goes down to the low 12’s and last 4-5 miles of my journey where it was at 14.1-14.2.



My question would be, is this normal behaviour for an alternator? I guess the clue is in the name…I’m guessing it doesn’t charge the battery when it doesn’t need to? So I shouldn’t be expecting it to be putting out 14.5 all the way through a 25 mile drive? Could I genuinely have issues with the VR, or the alternator?



On exiting the car last night I saw the battery drop down from 14.2 to 12.5v whilst I sat in the car



This morning, after that 25 mile drive with the heating, command and lights on last night, the car showed 12.5v prior to start and car started, but took a couple secs before firing – this was with no intervention from me. Alternator at 14.5v most of the journey and then down to 14.2 towards the end of my journey.



Thanks for everyone’s help. Hope this is of some use to someone in time to come – I will keep monitoring as ideally after a 40min/25 mile journey the battery should be able to fire the car on the button (Merc factory original glow pugs were replaced last year like-for-like Behr)
 

AMGeed

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How is this CCA reaching test done ?


This explains it far better than I can:D

"There are essentially two ways to test a battery. The "old fashioned way" is to use a Load Tester. For accurate results with a load tester, the battery must first be recharged before it is tested. The tester applies a calibrated load to the battery (typically half the battery cold cranking amp [CCA] capacity or three times its amp/hour rating). While the load is applied, the tester monitors battery voltage. If the battery voltage drops below 9.6 volts during the test, the battery is BAD and needs to be replaced. If the voltage remains about 9.6 volts, the battery is GOOD and can be returned to service."

Taken from this link which explains a lot about batteries.
https://www.aa1car.com/library/2003/us20310.htm
 

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