cadbob

I'm Curious what our cars Normal Amperage Discharge should be about. I just checked mine and I'm getting 26.2 mA and DC10A 2.62 depends on Multimeter Setting. Is that an Issue?

Vulcaneer

26.2 ma is not a problem. But 2.62 amp is a definite problem.

If you battery goes dead in a week or less, you have a problem some where. Connect your DMM and start pulling fuses to locate the faulty circuit.

cadbob

Attached is Meter I used all I did was turn dial and got the two readings. So that why I'm curious if I'm ok?

next2pool

2.6 amps is 2600 milli amps so I suspect that when you have the meter set at milliamps it gives you a reading that is in a factor of a hundred. Regardless, I suspect your drain is 2.6 amps which is a good sized drain if it is there all the time. Typically headlights are around 10, radio 10 to 20, so it could be a phone charger, courtesy lights, fog lights, and so on.

cadbob

I was afraid it was as you explained, was hoping it was other way around.
My Trunk Light is out, could a blown trunk Light Cause Drain? I can't figure out how to disconnect to replace the Trunk Light I have one ordered.

next2pool

I think an individual bulb like a trunk or glovebox only draws 1 amp if that. That will run down a battery in a day or two. If your trunk light is out, it won't draw anything at all. How are you measuring the draw since you need to insert the meter leads between the battery and the cable with the cable disconnected, unless you have an inductive meter.

cadbob

I ordered a clamp meter, but looks like I'm going to have to take it to the local Independent, I was hoping to avoid paying labor and replace part myself.

I disconnected the Positive from post, and used my meter to complete the circuit. One Lead on Wire and other on Post

next2pool

Sounds like you are doing it correctly. Is it possible to make a reading with the trunk closed as well as all of the other openings such as doors and hood. There are some circuits that "wake up" when trunk or doors are opened. Also, make sure the key is not in the ignition. Don't give up yet

cadbob

LOL, I know I hate giving up, but from being in Florida for 28 yrs and now back in the North East, where it feels like Hell Froze Over, and with no garage, I'm stuck wanting it fixed even thou I drive my truck this time of year. I just hate knowing it has a problem. She's my baby!

Vulcaneer

A blown light will not cause a amperage draw. It is a dead circuit. As such, a dead circuit uses no power. So no amp draw. Besides even if you have a functioning bulb, if the trunk lid is closed, the trunk light should be off by the switch. Unless the switch is faulty, and the light stays on when the trunk is closed. from your description, I doubt your trunk light is the problem.

Your meter is giving you conflicting readings. Get a good meter. It is wise to not take any reading for an hour after shutting the car off, turning off the ignition, opening /closing the doors, opening the hood/trunk lid, or energizing any individual circuits. Once a circuit wakes up, it could remain energized for an extended length of time, before it really shuts down completely. So best to connect a meter, and then shut everything down (or disable circuits) and then come back in an hour to take the readings. example: If you open the hood/trunk, remove the hood/trunk light bulb...to disable that circuit. If opening the door, hold the button closed so the dome light and interior lights do not energize.

Please answer this question....How long after a full charge, and without use, does it take your battery to go dead?

cadbob

Well got car back today, the Mercedes Mechanic confirmed I didn't full let car sleep and also I should of Wedge shut trunk switch. He said I'm pulling 30-50ma which is spec. I siad awesome maybe the new Interstate AGM is all I needed.

Well drove 10 miles, shut off ran into store, came out and when I turned Key to start as I got to ON before ignition the same old RED Battery appeared in Dash.

Vulcaneer

Bad Alternator. The battery is not charging while engine is running.

Put your DMM on the battery while the engine is running. Should read approx. 14.7V while charging.

cadbob

I did with everything on lights, radio, heater, etc I was getting 14.09 Rear/15.25 front. I'm thinking it is sporadic alternator failure. At RPM it is failing or Voltage Regulator is going in and out

Vulcaneer

When the key is turned to the "on" position, (before Ignition) it is perfectly normal for the red battery light to come on. It should go out when the engine is started. But to be showing the red battery light in key position number 2 is nothing to worry about. The reason the light comes on then is at that point the battery is NOT charging. And doesn't start charging until the engine starts and the alternator starts turning.

cadbob

Yes but at that point, the light stays on and does not go off till I bring it home and put car on charger and fully charge battery. I'm guessing the Cars Computer Systems does a quick look see before starting.

Driving along light never comes on, But after a bit of a drive I shut it off and re-start I get the Battery Symbol, which stays on till I get car home and put on charger. But before putting on charger the battery voltage is 12.55V

next2pool

A fully charged battery is 12.6 V after it has been sitting for a while. Normally after a run with a good alternator, the battery should show above 13 V with the ignition off. It has what is called a surface charge that gradually settles down to 12.6V. Also, it is not normal to get a red warning light with the ignition on and the engine off. Even though the voltages with the engine running are in the correct range, it looks like your battery is either not cherging or you have a bad or corroded connection in the system.

slk55er

By chance do you have a Valentine 1 radar detector installed with their "SAVVY" unit connected to the OBD connector? After buying my "SAVVY" unit, Valentine posted a disclaimer staying that this device will drain the battery on some vehicles (including Mercedes.) Within 4 days, my battery would be down to less than 9 volts so I am no longer using this product and have the V1 connected via a cigarette lighter socket.