Posted last year I had an issue with the RCM and the car wouldn't start. Sent that to DJ and he redid that. Got it back and car started right up. Sat for two months and battery was completely dead.

Discovered that I had high parasitic draw. I was getting around .6 amps when it should be like .05 amps. Took fuses out one by one including the RCM fuses, fuses on left side of steering column, and fuses under the hood on left side. The only fuse that changed anything was the radio fuse. It went from .6 to .18 which is still too high. Anyone have similar issues or know where else I should check? Thanks!

 

Most likely the alarm that is under the wiper cowl. The alarm has its own battery back up built on the circuit board. The battery leaks and damages the circuit board. You can find a retrofit or just disconnect it.

James

 

Awesome thanks! Looks like Mercedes 2198203226?? Possibly 219820322664 replaced it? Haven't found many options besides Mercedes brand. If I simply unplug will it throw a light on the dash or an engine trouble code at all?

Also is that alarm not part of the fuse systrm tho? I pulled all the fuses and still had the same draw unless the alarm is not fused like the module under the hood is?

 

The alarm siren is usually the part that goes bad. Here's a post I did when I replaced mine. The part number is in the post.
Alarm siren replacement and drain cleaning

 

Thanks! My only concern is I removed every fuse one by one and removing the security fuse didn't change the draw at all unless the actual alarm siren doesn't have a fuse in the fuse box or something?

 

On my 2006 it's fuse number 9.
Here's a video on how to chase a draw on an SLK 320 ( basically the same car as ours). I hope it helps.

 

Yeah I used a multimeter already and pulled every fuse. Pulling the security fuse didnt make my reading go down which is why I wonder if it's the alarm siren or not. Like I said unless the siren had its own built in fuse and doesn't go through the main fuse box.

 

The OEM radio is also known to cause issues as they age.

 

Removed that fuse as well. Dropped from .6 to .18 but still way above the .05 number.

 

Unless your alarm has been replaced it's likely the two 3.7v NiMH rechargeable batteries have failed and are leaking internally. Pull your windshield cowl and unplug it, then report back.

 

That was my plan. I did remove the fuse for security and alarm etc and nothing changed though. Maybe the alarm isn't fused through the normal box. Ill try that and see what happens. Thanks

 

There are a few items that are only fused thru the 200 amp fuse in the little box next to the battery, an example is the ICM (Illumination Control Module - headlight switch).
At the point you were at, the next step is to pull all the fuses from the ICM.
If that does not do it, pull the big red cable off the back of the alternator.
If that does not do it, pull the little wire/connector off the back of the alternator.

WARNING: Unbolting the alternator, if you keep it away from ground (the engine block), is the same as pulling BOTH wires off the alternator - so if you unbolt and dismount the alternator and the current goes to zero, pull the heavy red cable and tie it back, then remount the alternator to see what you have. IF you have current again, pull the little wire/connector and then re-mount the alternator for a second measurement.

 

Here is my guide:

 

I had this issue for about a year until the alternator burnt out. Turned out the alternator was drawing current all the time and flattening the battery in one week if not driven. Once the alternator was replaced the fault was gone.

 

One other thing, are you waiting to see if the car computer goes to sleep - when something changes like you pull a fuse, the computer wakes up to see what happened thus creating a larger current draw. Only after it goes to sleep can you really be sure of what's going on.
-Jerry

 

Okay so.....I learned i wasnt leaving the multimeter on long enough. I just hit it and it goes to .6 amps. Well it does this every time when you first hit the post. If you hold it on It slowly went down to .18 amps. I removed the radio and security fuses and got it down to .07. Wasn't holding it on the terminal long enough to get past the initial surge of juice.

I did just get the security alarm removed. It looked brand new though. Checked amps and was still at about .18. Took radio fuse out and stayed about .18 or .17. Took security fuse out and it went down to .07. The alarm is removed so not sure what else would be drawing that extra current from the security fuse. It controls trunk light, which we removed the bulb already. Roof lights which are all off, and the horn as well so not sure what the issue is. Frustrating....

 

That is why I wrote my guide, I tell you ahead of time what to do and what to watch out for. MOST of the time, finding excessive battery drain is not all that hard.
In most cases, I have it isolated in under 30 minutes.

There have been two cars that proved very difficult, one was a car that had a leaking pass transistor in the Climate Module - it was holding the duovalve closed (which requires over an amp of current) even with the key off.

Spec is "Less than 55ma (.055 amp)
Base/SE models will run .020 or so and limited/SRTs .040 to .055 or so; that is, when all is right with the car.

In any event, once you find the fuse that the extra current is passing thru, you can use the diagrams in the wiring chapter to find the item that is at fault.

 

Sorry I missed your guide!! Ill take a look tomorrow and use it. Still unsure why it drops by .1 when I take fuse 9 out. Its horn, roof lights, security, and trunk light. Trunk light is taken out and security alarm has been removed as well. I think someone already replaced the alarm because it looked brand new. Ill probably leave it out if it won't cause any issues anyways.

 

Check for corrosion in the roof lights. There are a bunch of exposed bars in the roof light assembly. If moisture got in there somehow, it may have corroded the bars and there may be a short caused by the corrosion. Just a thought.

 

I think we have it figured out. After several mins amps go down to .02!! I removed the siren alarm but not sure that was the issue anyways. I wasn't letting enough time for the draw to go down. Started .6 and after few mins went down to .02. Alarm looked fine but I guess could have been the issue. No way to test that now unless I put it back in. Ill leave it out and hope we're good now. Its a convertible so doesn't really have roof lights. Thank you everyone for the help!!!