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Hi
I have recently acquired an SL 500 , having driven it for approximately 360 miles with no issues ,with no warning the battery light illuminated followed by a loss in power momentarily .
Thereafter ,the SRS Light came on with EML light and ABS light all illuminated .
It was telling me that braking power was reduced and to visit workshop .
I pulled over into the next available services whereby it would not select gears.
I switched the car off and back on ,it then allowed me to select gears .
Since then ,I have had the codes cleared via RAC ,but having taken the car for a 2 mile drive ,it is flashing the warning lights up again.
It is also telling me that I have multiple lights out ,which they actually aren't !
Any help would be appreciated .
2014 E350 also restored: 1969 Camaro convertible SS 1957 Chevy Belair 2dr hardtop
Who ever you bought car from must have taken the charger off before you took posession. after it lost the full charge you a=started having problems. I will bet the person who you bought from new the batteries were bad.
The rear battery is much more likely to fail than the front.
If the car spins over nice and fast when it's cranking then the front battery is probably OK.
Get the right size AGM battery for the back, clear the codes and see how you go. The starting battery can go weak and be failing without throwing any dash messages, but a failing rear battery will throw the red battery message in the dash.
Im not 100% but I had a similar issue. It turned out to be the front passenger sam. Not as bad as your situation. I had light go out and brake warning come up. Also my glove compartment light was not functioning <—- this is a good tell.
So I pulled out the front sam, opened it up,used a toothbrush and 91% alcohol cleaned the sam of corrosion. After that all issues went away.
The rear battery is much more likely to fail than the front.
If the car spins over nice and fast when it's cranking then the front battery is probably OK.
Get the right size AGM battery for the back, clear the codes and see how you go. The starting battery can go weak and be failing without throwing any dash messages, but a failing rear battery will throw the red battery message in the dash.
Thanks again for the info
I will try all these things ,at least batteries are easy to check and replace .
Where would I find the front SAM and how esay is it to remove ?
Tested the batteries with engine running
Front was 14.77 v
Rear 14.46 v
That appears to be the batteries ruled out .
What were they before you started the car? Once it is running, you are seeing charging voltages. That said, your charging voltage probably wouldn't be that high unless they had a decent state of charge. Front passenger SAM is probably a good starting point.
Let it sit overnight and check the rear battery voltage before you start it up, then watch it as it comes up. If it comes up instantly that can indicate a weak battery. It should take about four seconds to come up. Those voltages you measured indicate the charging system is working OK.
Does it crank over strongly?
There was a post recently about blocked windscreen drains causing water build up under the fuse boxes in which case you should be able to pull them and clean them up.
Hi
Yes ,it appears to turn over quickly enough .
I took it out for a drive last night and within 3 miles it said reduced braking power , the headlights went out and the speedo dropped to zero .
Also ,on returning home ,it appeared that the steering was more stiff on turning than usual .
The front passenger SAM is responsible for many of the functions that you are having issues with. It controls the headlights, right marker and fog, SBC status is reported to it, most interior lighting, front brake wear sensor and washer fluid & coolant levels read by it, etc. On Mercedes, the fuse/relay blocks are directly attached to the SAMs. You need to remove the entire thing, separate the fuse block from the SAM, and clean all of those connectors. Also remove the fuses and relays and clean the sockets. If the corrosion is bad or you got water damage inside of the SAM, it may need to be replaced. You could also have power supply issues to the SAM, like an EIS going bad, but corroded front SAMs are fairly common, so it is a good starting place.
You should also consider at least a handheld Benz specific scanner. I have a Launch Creader Elite Benz edition, but there are several covered in this forum that will work. You are kind of flying blind without one. For example, you could read the SBC status line at the passenger SAM and the voltage at the SBC module to determine if you have an actual voltage issue at the SBC or an invalid status at the SAM.
Thanks again for that info .
After an uneventful 350 mile drive ,what would cause this issue to appear out of the blue .
It now throws a wobbler after only a 2 mile drive
I had exactly the same experience. I scanned the car and virtually every system had a fault code. The rear battery was not an AGM although it was checking out fine voltage wise, and it looked quite new. I changed it for a new AGM and cleared the faults. Everything has been fine since (3 years).
That sounds incredible .
The battery on mine is a Yuassa , it is the correct amp age and also appears new , I have tested it and it's putting 12.5 volts and 14.46 with the engine running .
I was reluctant to buy an AGM at £200 if this one checked out OK , however if it is indeed the make of battery I need to get it changed .
10-24-2022, 08:41 AM
