BATTERY TYPE Mercedes CLK 200 2009my today's date 13/05/20

[Rich69]

Hi, can anyone advise please?

I have a 2009 CLK convertible. Petrol. It has it's original battery.

The battery on my car is 12v 100AH 760 A.

Apparently the recommended replacement is 12v 77AH 780 cca. I ordered a new one to that spec which I am waiting to be delivered, due to the pandemic.

The car runs but the hood stopped working and diagnostics picked up nothing except a reduced ampage on the battery - no wonder if it's 11 years old!

I wanted to know if anyone can advise on why my car would have a 100ah battery?

Also any idea if that will solve my hood operation?

I already checked fuses, had diagnostics (some codes were in there but nothing on the database for them apparently). No lights on the dash when the car is running.

Hood switch works as the windows drop, mech whirrs at the back but tonneau doesn't move. Then when taking switch to 'close' the whirr at the back again, but windows do not go up. I then raise windows with window switches which work ok. (bit slow).

The oil level is good for the hood, it has never moved from almost at the midway line. The system seems to be working good as I put my phone in the boot and filmed as I operated the switch. (as you need the boot lid closed!).

Frustrating. I hope the new battery solves this.

Any expertise gratefully received.

Thanks for taking time to read this through.

 

[pmcgsmurf]

If your car has a 100Ah battery then changing this to 77Ah is just a smaller reduced capacity battery.

Very unlikely the battery would be the cause unless it was flat and did not have enough power to operate your roof.

Where did you get the info. for the recommended replacement, direct from Mercedes?

 

[Jockcl500]

If the battery fitted is a 100AH and it is original, then it is very unlikely to be the wrong one.
It is more likely the 77AH is the wrong info, depending who you want to belive
If I were you, checking the spec with Mercedes is the sensible option.

 

[ToeKnee]

Surely if the roof doesn't work with the engine running it can't be the battery? Wouldn't the alternator take over?

 

[Jockcl500]

Surely if the roof doesn't work with the engine running it can't be the battery? Wouldn't the alternator take over?

The battery powers everything.
The alternator charges the battery.
The alternator doesn't power anything, so NO it won't take over from the battery.

 

[ToeKnee]

If you say so, sorry I answered.

 

[Jockcl500]

If you say so, sorry I answered.

Sorry if I was a bit blunt, but I was just stating facts.

 

[wongl]

Surely if the roof doesn't work with the engine running it can't be the battery? Wouldn't the alternator take over?

I am with ToeKnee on this one, if the roof doesn't work with the engine running, I would be looking elsewhere for the problem.

 

[GP801]

There was an option for a high capacity battery fitted from the factory. I think its code 673 on the data card. It was fitted depending on what other options were fitted. Our SLK has it fitted because it has remote roof operation that does not need the engine running. Don't know what capacity it would be on a CLK but that may explain the discrepancy.

 

[pmcgsmurf]

The battery powers everything.
The alternator charges the battery.
The alternator doesn't power anything, so NO it won't take over from the battery.

You can actually start the car with the battery, then when started remove the battery and the engine will still run.

 

[55AMGCLK]

Try manually opening and closing the roof. If any of the limit switches are stuck, this should free them up.

The odd thing is that you are not getting the Visit workshop message.

What diagnostic tool are you using? Their are not many that will read out the fault codes from the roof.

 

[Jockcl500]

You can actually start the car with the battery, then when started remove the battery and the engine will still run.

Yes that is true but not recommended.
I'm not sure why you quoted me, as you probably know what I said is true.