LCD Display NOT shutting off
Thread Starter
Junior Member
Joined: Feb 2024
Posts: 20
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C2804Matic & E350
LCD Display NOT shutting off
About a month ago, I developed a parasitic drain on my battery but could not pinpoint it. Checked all fuses and relays and they are in working order.
Last week, I noticed that the LCD display in the instrument cluster does not shut-off when the car is not running.
Thinking this was the parasite, I pulled fuse #42 (instrument cluster) and the whole unit went black (off).
However, the battery (now a new one) is still draining somehow. I don't allow the new battery to go below 12.3V before I attach the Battery Tender to restore the charge.
In addition to the LCD light, I can hear a very faint noise a electric"buzz or maybe a micro fan. This noise remains even after individually removing each fuse and relay ( all three fuse boxes) to see if it gets silenced but that never does. The only time the sound goes away is if the battery is disconnected.
Can anyone shed some light on this mystery?
Last week, I noticed that the LCD display in the instrument cluster does not shut-off when the car is not running.
Thinking this was the parasite, I pulled fuse #42 (instrument cluster) and the whole unit went black (off).
However, the battery (now a new one) is still draining somehow. I don't allow the new battery to go below 12.3V before I attach the Battery Tender to restore the charge.
In addition to the LCD light, I can hear a very faint noise a electric"buzz or maybe a micro fan. This noise remains even after individually removing each fuse and relay ( all three fuse boxes) to see if it gets silenced but that never does. The only time the sound goes away is if the battery is disconnected.
Can anyone shed some light on this mystery?
MBWorld Fanatic!
Joined: Jun 2002
Posts: 7,263
Likes: 169
From: So. Oregon Coast
C230 Sport Coup + 2006 W164 ML350 + 99 Ford Escort RIP
Tracking crap like that down can be a PIA.
The most well known power drain is the seat modules.
Drain the battery overnight I've heard.
Have you tried disconnecting those?
Yes, I know you heard of a fan or something but worth a try.
Might be more than one thing.
Is your fuse box/Front SAM under the hood fully sealed?
Dried water can leave behind conductive materials
that causes wierd stuff.
Had something like that on our W164. They mount the battery in a
caverous hole under the passenger seat. And also there's a power distribution
PCB do dad. We were camping and a gallon bottle of water got crushed spilling in there
causing all manner of demonic possession of the vehicle. Lights flashing,
windshield wipers going, horn honking all the while stuck in traffic that had stopped with nowhere to pull over.
Just stuck there for the longest time with all this going on and people looking at us like WTF?
We made it home, and I disconnected the battery.
Next day, even after it was dried out, a number of things would not turn off. Fog lights just on for no reason and other things.
I found a video in Russian which fortunately Youtube translated where that power PCB was cleaned
with a toothbrush and WD40. And yes, all the problems were solved, wierd as it sounds.
The most well known power drain is the seat modules.
Drain the battery overnight I've heard.
Have you tried disconnecting those?
Yes, I know you heard of a fan or something but worth a try.
Might be more than one thing.
Is your fuse box/Front SAM under the hood fully sealed?
Dried water can leave behind conductive materials
that causes wierd stuff.
Had something like that on our W164. They mount the battery in a
caverous hole under the passenger seat. And also there's a power distribution
PCB do dad. We were camping and a gallon bottle of water got crushed spilling in there
causing all manner of demonic possession of the vehicle. Lights flashing,
windshield wipers going, horn honking all the while stuck in traffic that had stopped with nowhere to pull over.
Just stuck there for the longest time with all this going on and people looking at us like WTF?
We made it home, and I disconnected the battery.
Next day, even after it was dried out, a number of things would not turn off. Fog lights just on for no reason and other things.
I found a video in Russian which fortunately Youtube translated where that power PCB was cleaned
with a toothbrush and WD40. And yes, all the problems were solved, wierd as it sounds.
Last edited by C230 Sport Coup; May 31, 2025 at 04:59 PM.
MBWorld Fanatic!
Joined: Dec 2003
Posts: 3,275
Likes: 236
From: BC, Canada
2003 C230K Coupe Orion Blue
+1 for checking the power seat modules.
Modern cars are basically a networked bunch of computers on wheels. Not everything shuts off immediately when the key is switched off. For example, notice how the dome light slowly dims on/off.
The instrument cluster also doesn't just shut off immediately under all conditions. You may be seeing this in action. My SA mentioned that it takes 30 minutes for all modules to go into sleep mode, though anecdotally I found it to be more like 5 minutes.
Modern cars are basically a networked bunch of computers on wheels. Not everything shuts off immediately when the key is switched off. For example, notice how the dome light slowly dims on/off.
The instrument cluster also doesn't just shut off immediately under all conditions. You may be seeing this in action. My SA mentioned that it takes 30 minutes for all modules to go into sleep mode, though anecdotally I found it to be more like 5 minutes.
Thread Starter
Junior Member
Joined: Feb 2024
Posts: 20
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C2804Matic & E350
Yeah, I read about the passenger front seat and disconnected that, no luck. The front SAM was fully sealed. However, recently (before the parasite) I left my trunk open and it rained a bit. After that, I blew a relay in the rear fuse box (trunk). It was a 6 pin that controlled central locking, alarm system and window washer pump. I checked all other relays and fuses with a multimeter and they were functioning. However, a couple relays and the sockets had damp blue crud on the pins, base and dripping from sockets. After that, I removed the fuses and relays (of all three fuse boxes) sprayed the pins and sockets slots with 91% alcohol.
