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~180mA parasitic drain from F008 fuse (Antenna Module + Anti-Theft)

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04 e320. chased down a 180mV parasitic drain. I'll start with a short summary and a longer post for those wanting the details.


Have a ~180mV parasitic drain after car settles into sleep mode. Pulled fuse F008 in the trunk fuse block and instantly drops to 30-40mV which is the spec for sleep mode.

F008 is listed as Antenna Amplifier on all the internet searches. The original fuse block diagram that came with the car is very hard to read. Its alphabetically sorted by features rather than fuse numbers. Thus, F008 is listed in 2 places (Antenna + Anti-Theft). This led me on a ghost chase on Antenna section for awhile before turning attention towards anti-theft circuit to find the parasitic drain. Unplugged a 5 wire connector in the back of the fuse block to disable anti-theft and parasitic drain is gone (See wire 1-5 next to fuse 8 7.5A in upper left of the attached wiring diagram). This below thread helped (different car, different wire coloring, same principle)

E320 2004 Which Fuse disables Alarm System?
Fuse #8 blows

Likely failed Siren internal battery. Disconnected the siren (not worth replacing) and reconnect the 5 wire connector to preserve the tilt anti-theft function. No more parasitic drain. I guess car won't have siren but will blink like crazy :)

Here are the details

Setup for parasitic drain test in following way.

Drove 5min to top off both main (brand new) and SBC battery (2 years old). Both measures 12.7V disconnected. Setup VOM on 10A DC scale inlined between main battery negative post to negative battery connector to measure parasitic drain.

Hood + trunk open (latch activated closed to trick car to think both are closed. Open driver front door and block close the door open switch. All accessories off (car has no GPS/MB phone). Key not in ignition.

Drain after open/close driver rear door

0m0s 5A
+30s 3A
+30s 1A
+10s 850mA
+30s 400mA
checked back at 25m mark from closing door, 220mA

Pulled the 7.5A F008 fuse in the trunk and current draw goes to 30-40mA. F008 circuit consuming ~180mA

Drain after connecting main battery with inline VOM

Also see settling to 240mA in about 6min just connecting the main battery with VOM inline

0m0s 5A Dash lights up red message "BRAKE Longer stopping dist..." Presumably VOM line not supplying enough current to SBC and triggers this message.
+54s 1.75A Red Brake msg gone, dash now shows normal display
+30s 1.35A Dash display goes out
+34s 0.95A
+2m0s 280mA
+2m0s 240mA

Pulled the 7.5A F008 fuse and current draw goes to 60-70mA. F008 circuit consuming ~180mA

From reading about W211 sleep mode nominal power consumption, 40mA is normal, 60mA is max.

Antenna Amplifier

Disconnected the antenna amplifier (part 7 in link below) behind driver side C pillar panel. Didn't reduce power drain.

Antenna & Radio for 2004 Mercedes-Benz E 320 | MB Online Parts


Car does have original Tele-Aid (obsoleted) and dash displays SOS Tele Aid Not Activated each time key turns to accessory position so the car has built-in analog cellular. Friend's Lexus recently started having parasitic draw issues and traced it down to inactive GPS. I guess some network got turned off recently and car querying at higher frequency and draws power. Maybe similar with the inactive Tele-Aid that wasn't turned off via SDS?

I actually disconnected all power+antenna to the Tele-Aid unit under the trunk floor and didn't see the 240mA current draw drop. Didn't start the car with tele-aid disconnected. My understanding is SRS talks to Tele-Aid since they would want to know if you crashed.


After chasing ghost on antenna module, reviewed the original fuse diagram again saw anti-theft and found the thread above. Disconnected anti-theft connector and bingo, parasitic drain gone.


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