W203 CDI 220 Battery Drain

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New Member
Aug 14, 2014
cdi 220 w203

CDI 220 sports package 2006

Battery dead, got new battery and drove car for a few days and then left for 4 days battery dead again.

When Breakdown company came we tested alternator and that seemed fine.

After 10 mins approx there was approx 1.6 amp pull when all switched off so I entered car and we could hear some noises behind command, took out 64 fuse for command/audio and it dropped to approx 0.6 approx but was still hovering a little so we left it as that.
My command did show merc logo when starting but will check which version it is as seen problem with earlier versions.

I have no memory seats only switch buttons to move seat directions.
No engine light on.

Since fuse 64 has been removed battery drain has not occurred again but car has been driven every day. I need to be sure incase something else.

I will try another drain test on weekend, but this must be a common problem.
Can any advise which are the more likely elements that could cause this so I will work on those fuses first removing when I test with my multimeter.

Other Symptoms noticed :

Drivers side sun guard light stays on sometimes when sun guard left down when locked and larmed
Front interior lights stays on sometimes when locked and alarmed

I will open bonnet and is it best to wait 30 mins before testing, I will put bonnet hatches down to look like bonnet is shut do I need to do anyhing else before starting test by removing negative lead and connecting multi-meter?
I'd not recommend checking the current drain that way at all. IMO it's more likely to create further faults.

You best buy an meter that's purpose built for testing such issues, and has a special fuse style connector so you can measure the draw though each individual fuse.
The engine pre-heater on the 203s has been known as a source of high current draw when it's goosed. From what I've read, people simply disconnect it and insulate the connections, living without it.

I had the preheater block battery drain a few years ago. Don't think its that but will test it.
When that drained the battery it was in the space of 8 hours approx and drainage amp was showing 2.5amp approx.

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