SAM or not the SAM

[John77]

Well short version. Started with battery going flat in 2-3 Days See Post. Found that when the battery was re-charged it crackled on reconnection see Battery Crackle post. Found that on removing fuse 8 (Antenna Booster) that the crackle stopped on reconnection. Also with fuse 8 removed and the battery connected it has stayed at full charge for 4 days.
Then removed the Antenna Booster so that nothing goes to it and it's power wire is disconnected. On re-connecting battery with fuse 8 in, the battery still crackles. Removed all the fuses and relays of the rear fuse panel, SAM no crackle on reconnection. Put only the number 8 fuse back on the SAM again battery crackle. So is this now a SAM fault? Is there a way to check this? or just change it? Or something else?

***Most questions have been answered in the other 2 Posts***

At the moment the Fuses and relays are removed from the fuse panel, SAM.

 

[sonic]

As you say the drain in on fuse 8 & its not the antenna amp. You now need to work your way through the equipment connected to fuse 8, something is drawing current.

 

[John77]

As you say the drain in on fuse 8 & its not the antenna amp. You now need to work your way through the equipment connected to fuse 8, something is drawing current.

Thank you for the reply. According to the fuse list, the only thing coming off that fuse is the Antenna Booster. Which has been removed and no longer connected in any way. There is also a short somewhere that makes the battery crackle.

 

[Botus]

when we say crackles - do you mean as you connect the battery terminals current is flowing and you see sparks and maybe a tiny noise

or are you hearing noises from inside the battery ? if so that is not normal ever

 

[John77]

when we say crackles - do you mean as you connect the battery terminals current is flowing and you see sparks and maybe a tiny noise

or are you hearing noises from inside the battery ? if so that is not normal ever

Hi thank you for the reply. If you read the posting battery crackles it tells all, but no not from the terminal from in the battery and if I leave it connected it goes quiet after about 15 seconds and the the battery is totally flat in 2 days. See other posts, Battery goes flat, Crackle from Battery and what does the Antenna Booster do, which is where I started with all this and progressed to the SAM over the weeks of trying to find the fault.

 

[Botus]

I read one of your other posts and I got the impression you felt it was noise inside the battery... the only way that computes in my head is where something isn't right with the battery - most Mercs have an AGM battery absorbed glass mat (it started as out as a more durable battery for the military).

trying to use layman's terminology...

a std. battery has the lead on a plates surrounded by electrolyte (acid and water) then another plate etc. The lead is a bit like chalk or clay squashed flat and sits vertical (on its plate) and by luck stays in place. Then due to wear, vibration etc. when old enough chunks fall off and at it touches another plate as it falls past it causes discharge. As more and more falls off the charge capacity depletes, till one cold winter (often caused by freezing - I think in a healthy battery the electrolyte acts as antifreeze and a worn one doesn't), enough lead falls off that it remains touching another plate and its dead.

the AGM battery type doesn't have a gap for the lead to fall off, that's where the matting sits, then the "electrolyte is different" I don't really understand that bit.... but it ends up holding charge better, can charge harder, discharge harder and be chucked about and they take the abuse... But the matting can dry out and stops the battery functioning correctly. And I suspect this might be where you get the noise and a crap battery....

I have topped up gently 3 AGM batteries with small quantities of distilled water and recovered from unusable to good as new.... On the Merc AGM the lead plates look like black sheets 3mm thick surrounded by bone dry white tissue paper... when you top them up the paper swells up and surrounds the plates like they should be.... then 30 mins later it looks bone dry, so you add a bit more each time leaving for around 48hrs before screwing the lids back on - so it just looks damp and the plates are fully hidden and after a month of use its good as new... If you have AGM I'd give that ago, if a conventional battery I'd throw it out

 

[Botus]

FG 171.458 - ANTENNA > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes. Car. ANTENNA.

nemigaparts.com

 

[John77]

I read one of your other posts and I got the impression you felt it was noise inside the battery... the only way that computes in my head is where something isn't right with the battery - most Mercs have an AGM battery absorbed glass mat (it started as out as a more durable battery for the military).

trying to use layman's terminology...

a std. battery has the lead on a plates surrounded by electrolyte (acid and water) then another plate etc. The lead is a bit like chalk or clay squashed flat and sits vertical (on its plate) and by luck stays in place. Then due to wear, vibration etc. when old enough chunks fall off and at it touches another plate as it falls past it causes discharge. As more and more falls off the charge capacity depletes, till one cold winter (often caused by freezing - I think in a healthy battery the electrolyte acts as antifreeze and a worn one doesn't), enough lead falls off that it remains touching another plate and its dead.

the AGM battery type doesn't have a gap for the lead to fall off, that's where the matting sits, then the "electrolyte is different" I don't really understand that bit.... but it ends up holding charge better, can charge harder, discharge harder and be chucked about and they take the abuse... But the matting can dry out and stops the battery functioning correctly. And I suspect this might be where you get the noise and a crap battery....

I have topped up gently 3 AGM batteries with small quantities of distilled water and recovered from unusable to good as new.... On the Merc AGM the lead plates look like black sheets 3mm thick surrounded by bone dry white tissue paper... when you top them up the paper swells up and surrounds the plates like they should be.... then 30 mins later it looks bone dry, so you add a bit more each time leaving for around 48hrs before screwing the lids back on - so it just looks damp and the plates are fully hidden and after a month of use its good as new... If you have AGM I'd give that ago, if a conventional battery I'd throw it out

Thank you for the reply. The original battery on the car was going flat in 2 day so brought a brand new battery. On putting it on I heard the crackle, but thought that it was the CD changer starting up, which is in the glove box behind the battery. The new battery goes flat in 2 days. Then I noticed that the crackle is coming from the battery. Listened also through auto stethoscope. It comes from the battery, every time it is connected after charging. Put on the old battery and the same crackle and in flat 2 days. Took out fuse 8 this has stopped. see other post on Antenna booster. Since fuse 8 has been removed, the battery has stayed fully charged for 5 days now. So something on the SAM is the problem. If you are close come and see.

 

[star]

Your guessing going on a “battery crackle or spark” Connect an amp meter to diagnose it properly.

 

[John77]

Your guessing going on a “battery crackle or spark” Connect an amp meter to diagnose it properly.

No spark. Surely if removing fuse 8 stops the crackle and battery drain. Something on the SAM must be the problem no?

 

[John77]

Ok now onto the SAM. I am retired so I have all the time in the world, (well 5 more years if you get 3 score and ten lol). to take things apart and use logic to find the fault. If you remove something and the fault stops it must be that. Anyway removed this plug, see photo and the crackle stops on re-connecting the battery. Just need to find out what this plug runs. see parts number on second photo. Third photo shows the position of the plug on the SAM. Probably runs something stupid. I have just rang MB and the say that it runs the theft and tow away sensor. So on we go Ha! Ha!

 

[sonic]

No spark. Surely if removing fuse 8 stops the crackle and battery drain. Something on the SAM must be the problem no?

Get or borrow an amp meter its the only way you can certainly confirm a current draw. It will also help when checking the other circuits on this fuse.

 

[John77]

Get or borrow an amp meter its the only way you can certainly confirm a current draw. It will also help when checking the other circuits on this fuse.

Thank you for the reply. If you read my earlier post on flat battery. I already did this pulling all the fuses on all 3 fuse panels and nothing was really that different apart from 3 fuses that showed SOME drain. Followed the link given by a kind member which showed how to do this on you tube. The fuse is now reinstated and everything now works, doors etc, but what ever I have unplugged now won't of course, but MB say that that plug runs the Theft/Towaway sensor. Or there could be a problem with actual SAM circuit board running that plug. I could always put an amp meter on and reconnect the plug, then disconnect and see the difference, but seems a waste of time as the battery is not going flat now or the Battery is not crackling on reconnection with this plug removed. If removing this plug has solved these two problem, then it only goes to show that the problem is either within the circuit/components of this wiring loom or the SAM circuit board for that plug socket.

 

[sonic]

Sounds like a bad connection which has cleared with your disconnecting / connecting.
As its no longer drawing current I would tend to leave well alone. If it comes back you know where to start looking.

 

[Botus]

so the alarm is (was) causing massive power drain? does it start OK now?

 

[John77]

Sounds like a bad connection which has cleared with your disconnecting / connecting.
As its no longer drawing current I would tend to leave well alone. If it comes back you know where to start looking.

The plug has not been re-connected it is still disconnected.

 

[John77]

so the alarm is (was) causing massive power drain? does it start OK now?

The plug for that is still disconnected, but everything else seems to work I just need to find what is connected to that wiring harness.

 

[Taffy7hfa]

Get yourself a multi meter they are cheap as chips (screwfix do one for £7.99) and are really useful bit of kit.
it'll make finding your parasitic battery drain much easier.

 

[John77]

Get yourself a multi meter they are cheap as chips (screwfix do one for £7.99) and are really useful bit of kit.
it'll make finding your parasitic battery drain much easier.

Hi I have one could you explain what I need to do with it and how I do this to find the drain on this one wiring harness? I am only in Aylesbury, you could show me.

 

[Taffy7hfa]

There are loads of tutorials on you tube, this ones pretty good