E220 Cab 1996 - power drain

1986-1995 : 200TD, 200CE, E200, 260E, 300E 2.6, 300E 2.8, 300E, E320, 400E, E420, 500E, E500, 300CE, E320, 230TE, 300TE, 300D 2.5 TURBO, E300 DIESEL, 300TD, 300E 4MATIC, 300TE 4MATIC, E36 AMG
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Wally
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Model you own: w124

E220 Cab 1996 - power drain

Post by Wally » Sun 13 Nov, 2016 2:20 pm

Before I start troubleshooting, need some help.
In the last 6 months over Winter, the battery has been going flat if left for over 2 weeks. Since it was new in early-2008 and 8yrs is a good run for a battery, I guessed it was the battery, and replaced it (with the correct huge monster). All was well, until I went OS for 2 weeks - and lo! it was flat when I returned last week. Obviously there is an illegal drain somewhere. Everything else in the car is fine.

I have checked the obvious: boot light, door lights, interior lights. Next step is to remove all fuses, monitor the stand-by current, and progressively replace the fuses to see what is causing it. Does anyone know what normal standby current should be? I'd guess 50mA max. OS fora suggest its a common problem caused by electric seats (not got) and/or heated seats/power windows module. Anyone got an idea about what might cause this?

I haven't checked my standby current yet - thats a job for next week. I suggest I'll find its more than 200mA.
95 E220 Cabriolet 'Lil'
89 F**d SA1 Capri Turbo 'Rocket'
06 F**d Fairmont Ghia V8
13 Sooby Tribeca

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Wally
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Joined: Mon 26 Apr, 2010 3:52 pm
Model you own: w124

Re: E220 Cab 1996 - power drain

Post by Wally » Wed 14 Dec, 2016 6:21 pm

Well, an update on the power drain:
It measured about 5mA - nothing really. So what was causing the drain? After weeks of searching, and passing by the open bonnet one day, I heard a relay chattering. I leapt over to the fuse box, but it stopped. During the next 3 days, I waited for this elusive chattering relay to do its thing when I was close by: finally, I found it was relay K24 in position F, in the lower part of the relay tray. The relay was hot, and marked 40A, a very likely source of the drain, although intermittent.

But what does relay K24 do? On the fuse box lid, it was marked as 'front seat adjustment, jack tube adjustment'. Although I have the Brooklands W124 manual, the wiring diagram is incomplete (obviously) so K24 was unmarked. A Google search indicates it might be connected with the comfort pack, but I'm unsure. What I need is a 1995 Cabriolet (A124) wiring diagram - does this forum have such a thing? I can't find one on Google, but I can get very close. I'll be starting with the power supply to the relay, which appears to be set by the door closed switches - but that could be way off.

Any suggestions welcomed!
95 E220 Cabriolet 'Lil'
89 F**d SA1 Capri Turbo 'Rocket'
06 F**d Fairmont Ghia V8
13 Sooby Tribeca

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Boyracer
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Model you own: w123
Location: Sydney South

Re: E220 Cab 1996 - power drain

Post by Boyracer » Thu 15 Dec, 2016 3:05 pm

I wonder if your car has an old alarm system? If so, this would be my first guess.

I recently disconnected the old alarm in my Mum's car which she's had since 1988. She doesn't do much driving any more and it's weeks between use. Before I had the alarm disconnected, the car would need charging every couple of weeks. Now it lasts at least a couple of months between charges.
Cheers,
Michael

'85 Mercedes Benz W123 230E [929 Nautical Blue Metallic]

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Wally
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Joined: Mon 26 Apr, 2010 3:52 pm
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Re: E220 Cab 1996 - power drain

Post by Wally » Sun 21 May, 2017 12:43 pm

An update on the power drain - and to end this thread.

I did mention that this problem was after a new battery - about 6 months previous? So clearly, the battery wasn't a problem, was it? Not true.
When I started looking at less obvious things, I thoroughly re-checked the battery - and yes, one cell was going low.
Ive just read that wonderful thread on Battery Life in Australia, and never were truer words said: the main problem with my chattering relay was lowering battery voltage, and an ECU that was getting cross. It was getting marginal at 11.6 volts, and failed to start the engine at 11.0 volts - not from insufficient current, from insufficient voltage to run the ECU! I then couldn't charge it past 11.0 volts, and the battery was replaced under warranty.

Hey presto, chattering relay went away. I keep it on trickle charge now, because it is not a daily driver.
95 E220 Cabriolet 'Lil'
89 F**d SA1 Capri Turbo 'Rocket'
06 F**d Fairmont Ghia V8
13 Sooby Tribeca

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Ivanerrol
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Model you own: w204
Location: Melbourne

Re: E220 Cab 1996 - power drain

Post by Ivanerrol » Sun 21 May, 2017 5:45 pm

What brand battery was the faulty?
Check the date stamp on the new battery - it's on one of the posts or there will be a code.

Some of those monster batteries sit on shelves in the warehouse or in the retail store for quite a while before they are sold.

Not many cars use those DIN 88 and above sizes anymore. Since stop/start has been introduced many cars are now equipped with AGM.
W211 - E240
W204 - C280
W202 - C180
W210 - E240
Departed
W202 - C200
W202 - C180 - On consignment to nephew
W126 - 380SE , 380SE (Ex SA Import), 560SEL
W124 - 300e, 260e (ex Japan)
W111 220s (Indonesia) 4 speed manual column shift
W123 230
W116 450SEL
W140 420SEL
W210 E240
W209 CLK 240
W201 190e 2.6 (ex U.K.)

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