Got a 2004 E55 which had the battery / alternator stop vehicle red warning. Changed the Bosch regulator on the alternator for a Holger Christiansen one (now owned by Bosch) and the warning was gone. Car was off the road for a few months then when I came to use it again after driving it for 10/15 minutes got the Battery protection: Convenience functions unavailable warning on the dash then a moment later the battery voltage too low comand will switch off warning. After about another 5 minutes all functions switch off including the heater blower motor fans and I just get basic functions to use. I've charged my battery no difference, then tried a difference battery....no difference and fianlly a different one again....no difference!
I've put Star on it and found the following codes on the BCM which came back even after clearing: 9055 - Terminal 61 signal on CAN bus missing or faulty but can be ignored if no issues experienced, 9071 - Component K57/2 Auxiliary battery relay or signal wire faulty and 9092 - auxiliary battery defective ir not installed.
Anyone got any ideas where I start? Have charged the smaller auxiliary batter and never seemed to have issues taking charge and I've had a multi meter to the main battery and that seemed to be a stable 12 to 13 volts on idle but rises once revs increase.
Component K57/2 Auxiliary battery relay or signal wire faulty and 9092 - auxiliary battery defective or not installed. Anyone got any ideas where I start?
Replace relay part # 0025423819, see attachment. If needed, reference auxiliary battery OEM part # 2115410001.
Not been around for a while but have gone back to this and found even when running the voltage recorded on the dash is only 11.7 volts. Does this mean the replacement alternator regulator has an issue? Also I'm surprised that such a low voltage doesn't flag up the red battery light!
Anyone? Tested again today and on normal idle it's at 11.7 volts which lowers to 11.3 if the climate blower is turned on and if revs raised to 2500/3000 then it goes up to 12.5 volts but then lowers back once revs are lowered.
I didn't test the alternator, just changed the regulator which extinguished the red battery warning so thought the issue was sorted but as mentioned it's not charging the battery. Would have thought with such a low voltage being put out it'd keep the red battery light on??
Red battery warning comes with delay, so that might be why you don't see it yet.
Cluster display usually shows voltage at ECU, what is 0.5 V lower than on battery clamps, but still your car has no charging.
Is the low voltage still the same when you rev the engine?
Red battery warning comes with delay, so that might be why you don't see it yet.
Cluster display usually shows voltage at ECU, what is 0.5 V lower than on battery clamps, but still your car has no charging.
Is the low voltage still the same when you rev the engine?
I've drove the car around for miles and no red warning light still, just notice the battery is getting low so convenience features are turning off. Voltage goes up a little (around 12.5 volts) at 2500/3000 revs.
I've drove the car around for miles and no red warning light still, just notice the battery is getting low so convenience features are turning off. Voltage goes up a little (around 12.5 volts) at 2500/3000 revs.
13V is charging. Especially when you read it after 0.5 drop.
14.2V is actually shortening battery life.
It was W210 who was keeping 13.9V (actual) volts and batteries lasted up to 17 years.
New regenerative systems pump up to 14.7V and when they save fuel and enviroment, the batteries die faster than 4 years.
13V is charging. Especially when you read it after 0.5 drop.
14.2V is actually shortening battery life.
It was W210 who was keeping 13.9V (actual) volts and batteries lasted up to 17 years.
New regenerative systems pump up to 14.7V and when they save fuel and enviroment, the batteries die faster than 4 years.
13V is charging. Especially when you read it after 0.5 drop.
14.2V is actually shortening battery life.
It was W210 who was keeping 13.9V (actual) volts and batteries lasted up to 17 years.
New regenerative systems pump up to 14.7V and when they save fuel and enviroment, the batteries die faster than 4 years.
What makes you think 14.2 is shortening battery life?
14-14.5v is normal operation for the alternator.
Across the several Mercedes I have owned 14+ volts is normal operation when charging a battery.
13v 'charging' would take a very long time to charge a low battery.
As for battery life span, it depends on the type.
AGM can take high charging voltages without issues while 'cheaper' battery types will have issues.
OP idling at 11.5 and only seeing 13v with a low battery is a clear indicator of bad alternator.
Battery maintainers keep the voltage at 13.5V for wet batteries and that is what extends their life.
Anything above is sacrificing life for faster recharging.
11.5V at idle is dying battery. But it takes more to test. Is it real 11.5, or measured at ECU?
Idle alone is not much load, but was the blower and lights on?
regardless the details, 11.5V is car running on battery power with dead charging. ,
Battery maintainers keep the voltage at 13.5V for wet batteries and that is what extends their life.
Anything above is sacrificing life for faster recharging.
11.5V at idle is dying battery. But it takes more to test. Is it real 11.5, or measured at ECU?
Idle alone is not much load, but was the blower and lights on?
regardless the details, 11.5V is car running on battery power with dead charging. ,
So are we saying dead battery or alternator? I've tried various different batteries (have a collection of cars) and the problem is the same.
Battery maintainers keep the voltage at 13.5V for wet batteries and that is what extends their life.
Anything above is sacrificing life for faster recharging.
11.5V at idle is dying battery. But it takes more to test. Is it real 11.5, or measured at ECU?
Idle alone is not much load, but was the blower and lights on?
regardless the details, 11.5V is car running on battery power with dead charging. ,
Maintainers use a float charging after the absorption charge phase is over.
Absorption phase is about high 14v for AGM batteries, less depending on others.
High alternator charge voltages aren't harming the batteries.
Once battery is the charged it is only getting a float charge to maintain it.
Original auxiliary battery was an AGM battery, lasted 55K miles, 8 years.
Replaced it with a sealed but not-AGM battery which lasted 50K miles, 5 years when red light came on again.
Voltage of the aux battery was 11.5 volts at that point.
Easy to replace, see your local motorcycle accessories shop. ~$60
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