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* Registered
2005, Mercedes, SLK 350, 3.5, Automatic
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8 Posts
Discussion Starter #1
Hello, I am trying to figure out the cause of the battery drain. I checked the fuses and fuse 29 on the driver panel was causing drainage(car wasn't running). It is for the air conditioner. Car battery would die in about 1 day sitting in the garage.

Also, the car is dropping a lot of water every time after a drive. Is this normal? Or could be related to the issue?

Does anyone have a guess what would be the cause of it? Has anyone come across a similar issue?
 

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2007 SLK280, Silver!
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16 Posts
When you say dropping water, is it a puddle under where the gear selector would be?

That puddle might just be AC condensation from the drain. This might line up with your electrical issue (if its dropping while the car is running).

Its possible you have a relay that is fused closed - maybe the AC compressor relay. Do you have excessively cold AC when the engine is running?

When you remove that particular fuse, do you hear a click sound, which might be the AC clutch disengaging?
 

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2005, Mercedes, SLK 350, 3.5, Automatic
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8 Posts
Discussion Starter #3
590730
590731
590732

Forgot to add the pictures and car model 2005 slk350 automatic

When I removed the fuse first fault disappeared P0073.

Maybe it might be related. Just adding it here. I had top up coolant 2 times in last 6 months.
 

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* Registered
2007 SLK280, Silver!
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16 Posts
That doesn't look like the normal spot where the ac evap drain is.

The coolant circuit error is probably due to you removing the fuse to the pump (assuming its electric and not mechanical - I don't know). Can you see a leak from anywhere after it reaches temp?
 

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* Registered
2005, Mercedes, SLK 350, 3.5, Automatic
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8 Posts
Discussion Starter #5
That doesn't look like the normal spot where the ac evap drain is.

The coolant circuit error is probably due to you removing the fuse to the pump (assuming its electric and not mechanical - I don't know). Can you see a leak from anywhere after it reaches temp?
Coolant circuit error was already there. We reset the codes didn't help. Removed the AC blower motor and multi-function sensor (next to the battery). It didn't help with the Voltage issue. Guessing either one of the cables is bad or something else confusing the computer. When we remove the fuse voltage issue is good and of course I can not use the AC.
 

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Premium Member 2005 SLK350
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2,504 Posts
The fan speed regulator can short out internally and casue the fan to run constantly. The regualtor is separately replaceable.
 

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* Registered
2005, Mercedes, SLK 350, 3.5, Automatic
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8 Posts
Discussion Starter #9 (Edited)
You need to do a parasitic draw test
Basically that is what we have already done.

We connected battery to a meter. When fuse 29 pulled out. Voltage goes to normal.

Then we tried
1) Disconnect ac blower motor and fuse plugged in. Voltage was still high.
2) Disconnect - multi function sensor(module next to battery) and leave fuse plugged in. Again didn't help voltage use was still high.

So far only thing that help with voltage is removing the fuse.

591513
 

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Premium Member 2004 SLK350
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5,269 Posts
You did not find the right fuse, check also the inside fusses, also maybe the one ones in the rear sam. Make sure you give the car time to go to sleep.
 

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2005 Slk350 auto
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40 Posts
As mchild said fan rheostat have had it on bmw a lot where the fan constantly runs at slower than 1 so it’s not noticed.The live to the rheostat is permanent live so will drain with ignition off.
 

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2005, Mercedes, SLK 350, 3.5, Automatic
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8 Posts
Discussion Starter #12
You did not find the right fuse, check also the inside fusses, also maybe the one ones in the rear sam. Make sure you give the car time to go to sleep.
Why do you say it is not the right fuse? When I pull it AMP changes from 0.3 to 0.025.

And yes waited for the car to go to sleep. Doors are locked.

Image after fuse removed.
591569
 

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* Registered
2005, Mercedes, SLK 350, 3.5, Automatic
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8 Posts
Discussion Starter #14
Did you resolve this ?
Nope couldn't. We don't know what is causing this. We were hoping to fix this in the garage but looks like it will be more complicated. Trying to find a hoist that I can borrow for few days. If not, I guess I will leave it to a mechanic.

At least we were able to track it down a bit, but I feel like we are far from it. If I can find a hoist we will take it apart and check all the cabling other than that not sure what else we can do.
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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5,515 Posts
It's interesting to me that this fuse is mentioned twice on your paper legend, but the wiring diagrams show only one connection - a red/blue wire to the blower regulator. (not the smaller blue/violet wire). If the wiring diagram is correct, the next step would be to disconnect fuse 29, find the hot side, then check for a short to ground on the other side. This wiring passes from the fuse box at the end of the dash (behind the light switch) to the blower motor area, so it's routed behind the radio area - have you had any work done there?
 

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2005, Mercedes, SLK 350, 3.5, Automatic
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8 Posts
Discussion Starter #16
It's interesting to me that this fuse is mentioned twice on your paper legend, but the wiring diagrams show only one connection - a red/blue wire to the blower regulator. (not the smaller blue/violet wire). If the wiring diagram is correct, the next step would be to disconnect fuse 29, find the hot side, then check for a short to ground on the other side. This wiring passes from the fuse box at the end of the dash (behind the light switch) to the blower motor area, so it's routed behind the radio area - have you had any work done there?
Can u clarify what do you mean the hot side? Do u mean check at the blower motor connector to see if there is voltage if fuse 29 is removed?
 

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Premium Member 2005 SLK55 AMG; 2005 SLK350
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5,515 Posts
No, I mean remove the fuse 29 to expose both its connectors on the fuse panel, and measure voltage between each connector and battery negative. One should show 12v, the other should show 0v. The one showing 12v is the "hot side".
 

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Registered 2005 SLK55 AMG & 2006 Kleemann 55K S8
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1,027 Posts
I saw somewhere that the resistor on the blower motor can go bad and leave it slowly running while it should be off. Sounds like your issue.
 
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