Charging issue

[chris clk320]

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 doesn't leak but wobbly idle still there.

Its quite 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 wouldn't 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.

 

[Montreal300]

Your alternator voltage is fine. Check battery voltage for 12.6 nominal and then load test the battery to see if it meets the stated CCA written on the battery.
Although the running idle issue and battery shouldn't be related , these cars are very sensitive to voltage problems. The ECU will go a bit nuts if cranking voltage drops below 10V.

 

[chris clk320]

Your alternator voltage is fine. Check battery voltage for 12.6 nominal and then load test the battery to see if it meets the stated CCA written on the battery.
Although the running idle issue and battery shouldn't be related , these cars are very sensitive to voltage problems. The ECU will go a bit nuts if cranking voltage drops below 10V.

Thanks, i am surprised that the voltage is fine, i usually say anything below 14v is saying somethings wrong. The battery is fairly new but i will be having a good look over it this weekend so will report findings.

I have heard that voltage issues do affect other modules and ecu's

 

[DSM10000]

Thanks, i am surprised that the voltage is fine, i usually say anything below 14v is saying somethings wrong. The battery is fairly new but i will be having a good look over it this weekend so will report findings.

I have heard that voltage issues do affect other modules and ecu's

I would expect over 14V from the alternator at idle with no load.

What is the condition of the engine earth strap?

 

[chris clk320]

I would expect over 14V from the alternator at idle with no load.

What is the condition of the engine earth strap?

Thats what i would have expected, hence thinking voltage regulator, slipping belt or fubar alternator. Ill check the earth strap and all connections before i swap out parts

 

[Montreal300]

Alternator output varies according to the demand from the battery condition monitor. It does not have a fixed rate output.

 

[chris clk320]

So managed to have a good look this weekend, and tbh i am none the wiser.
Charged the battery overnight, charged fine, started fine.
with a multi meter the battery didn't drop below 12 when cranking had 14.1v going in so i can only assume that the charging side is fine.
Checked it for a parasitic drain 0.4milliamps so not much
Left it overnight still 12.5v in the morning Sunday started fine.
Started fine Monday morning.
Will run it this week to see if it gradually drains itself.

 

[Montreal300]

So managed to have a good look this weekend, and tbh i am none the wiser.
Charged the battery overnight, charged fine, started fine.
with a multi meter the battery didn't drop below 12 when cranking had 14.1v going in so i can only assume that the charging side is fine.
Checked it for a parasitic drain 0.4milliamps so not much
Left it overnight still 12.5v in the morning Sunday started fine.
Started fine Monday morning.
Will run it this week to see if it gradually drains itself.

I think you should be OK. I've found that sometimes, if my key is too close to the car, the ECU wont go to sleep which drains the battery.