Battery dying

[Snowy90]

Hello All,
MY w124 e220 coupe has been behaving strangely recently. 123,000 miles

First rear back drivers side window has stopped working- im sure not related but thought i would mention it.
Sunroof was stuck open- changed fuse and had a clean of the fuse seats and it started again.

However, i was getting a wobbly idle about 700rpm but the needle is ever so slightly wavering.
I did notice a slight weep of fuel on the disc shaped i assume vacuum actuator on top of the engine- replaced the little rubber hose connections doesnt leak but wobbly idle still there.

Its quote noisy in the engine bay like a fast grinding, not too severe but it doesnt sound sweet.

Anyway last few days its taken a few turns to start and feels slugglish to start. Yesterday very slow to start, even slower 2 hours later, then dead after a 30min drive and an hour in the dentist wouldnt start.

Fortunately i had a jump starter with me got it going. Now on the drive for inspection.

I haven't measured direct voltage at the battery yet or at the alternator but a little gizmo plugged into the 12v socket seemed to show fluctuating voltage between 13.4v upto 14v

So i automatically suspect the Alternator, but read it could be the regulator or even a slipping fan belt. I think the grinding noise is probably the idler pully? so my first port of call was to change those.

Just wondering if any of these issues are related? or whether to just go for a new alternator?

Thanks in advance.

 

[Snowy90]

Anybody?

 

[brandwooddixon]

An alternator is pretty pricey.
I'd start with the inexpensive parts first.
It looks like you've several issues.
First take off the drive belt and check all of the pulleys for odd movement and feel in rotation. Not uncommon for idle pulleys to fail.
Poor engine idle could be number of problems - vacuum leak, MAF, coil, plugs or leads.
Could the battery drain be caused by the rear window or sunroof? You could try removing the fuses for them once they're closed to see if the drain persists.
Charging voltage seems good so I wouldn't immediately suspect the alternator, although a regulator change (if possible) would be a first step, rather than a whole unit.

 

[Snowy90]

Thanks, I will be doing some diagnostics at the weekend so will check it all out.
I have always assumed under 14v indicates a charging issue but you think these are ok at those variables?