purdiemerc

Hi
My car is a S550 W221 2009 ( Fuse 133 is not used for reversing camera in my model)
I need to Power the Fridge in my recently purchased Adria ALtea 402PH Caravan, but only when the Car is running and also provide Power to the relay box provided with my Towbar which is used to activate Turn signals stop lights etc. on the caravan.
I am trying to determine how to use the available fuse outlets on the Rear SAM that are designated for Trailer Hitch these are Fuses 133, 145, 146, 151
Does anyone know what the normal use of these Fuses is ?
Fuse 133, only has 12V if ignition is in positions 2 or 3 but Fuse is designated as 15A and fuse in Caravan for Fridge is 20A.
Can 133 be used with a 20A Fuse to power the Fridge in the Caravan only when care is running ?
Or can I only use this output to switch my own Relay with in-line fuse (50A) from car battery to power the Fridge?

I have searched the internet and MB Forums without any success and would appreciate any help I can get.

Desperate for any Help
Purdiemerc

BOTUS

running high power items is best done with big cables direct to the battery and stitched via a relay - use the smaller fuses on the SAM to switch the relay and that way the device works well and your SAM isn't glowing in the dark struggling to cope

streborx

It's unlikely your car's battery and alternator are suitable for powering your RV's appliances. You should setup your RV with large capacity deep cycle marine batteries capable of running your fridge while driving and then charge the batteries while parked overnight. If off grid, use a small portable generator for charging.

purdiemerc

Hi Botus

That was my backup plan (use133 to switch a relay, but do you know what the other fuse /outputs 145, 146 and 151 are used for ?

purdiemerc

Thanks for your reply steborx
The caravan is small and has a small fridge and a gell/acid battery, we travel large distances in Australia and can be on the road for up to 12Hours so I do need to run the small 20 Amp 12V fridge while driving.

streborx

Understand -- nobody wants a warm Tooheys after 12 hours on the road! But 20 amps is a signicant load on your starter battery, which might be only 80 amp-hr rated, and on your alternator's output (especially if you drive with your headlamps on for safety). Being stranded with a flat battery would be a long walk home, and would seem even longer with only warm beer to drink.
What's the rating of your RV battery?

BOTUS

facelift allegedly

130 30 Electric parking brake module
131 7.5 Antenna amplifier module above rear window
133 15 Trailer recognition module 5 Rear View Camera
134 15 Luggage compartment socket
135 7.5 Radar Sensor Module (SGR) - PTS module (PARKTRONIC)
136 7.5 Engine 642.8: AdBlue ® control unit
137 7.5 From 1.9.10: Rear view camera
138 5 Navigation processor (Taiwan, up to 31.8.10) - Emergency call system module - TV / tuner plug connection (Japan)
139 15 Refrigerated box in the rear seat back
140 15 Cigarette lighter plug with ashtray lighting, rear 115 V socket
141 5 Rear view camera control unit - Rear view camera power supply module
142 7.5 PTS module (PARKTRONIC) - Radar Sensor Module (SGR) - Video sensors and radar sensors module (from 1.9.10)
143 25 Rear seat module
144 25
145 20 AHV trailer coupling, 13-pin
146 25 Trailer recognition system
147 - Reserve
148 25 End sleeve for panoramic sliding sunroof terminal 30
149 25 Panoramic sliding sunroof control module
150 7.5 Combo TV tuner (analog / digital) - TV / tuner plug connection (Japan)
151 20 Trailer recognition system
152 25 DC / AC converter

purdiemerc

Thanks Botus
I have a similar list but the description of "Trailer Recognition" on multiple outputs, does not help to identify what the output is used for.
The following fuses are not installed (no Fuse Holder) in my Rear SAM 133, 236, 237,138, 139, 146, 147, 148, 149, 151, 152, 120
I have piggybacked off 117 which is the trunk cigar lighter, for power to an small electronic module and camera, which I have installed to automatically swap the Comand Backup Camera to one installed on the rear of the Caravan when it is connected and when I select reverse, this works well.
I need to use at least one of the "not installed" fuse outputs to power the relay box supplied with my Towbar, which enables the Brake lights, turn blinkers and taillights of the caravan. Then if I cannot supply the fridge from the Rear SAM directly I will supply that connection via my own relay (switched by 133) directly from the battery to an Anderson connector to the fridge ( the usual way in Australia), but this involves running a heavy wire from the front of the car back to the boot which is difficult.

So what I am after is:-
One outlet from the rear SAM on circuit 15 (i,e, switched on by ignition) to supply at least 20 Amps or more directly to the Fridge.
and another outlet from the Rear SAM to sullpy power to the towbar relay box.

Another general Question I have is; does the SAM monitor / measure the output current of the fuses attached to it.
purdiemerc

purdiemerc

Thanks for your reply streborx
The battery in my Car is 95Ah the gellacid in the Van is 100Ah
The caravan manufacturer recomends charging from the Car to run the fridge, only when the engine is running.

Purdiemerc

BOTUS

there are a lot of spare take offs on the SAM mostly for all the possible extra options - they function the same - most are low current stuff - although I see the rear seat modules 143 and 144 are 25 amps each - if your car doesn't have this they might be a good idea as the car expected these to draw lots - but would still be best to set up your own separate power feed... the cables they use these days are on the edge of glow in the dark and the seat aims to run 15 mins then have a rest

not entirely sure what its measuring when and why - its a Merc they like to keep us in the dark - the Rear SAM has loads of stuff it is ambiguous to me maybe it pulls it together for some charging algorithm ?
BM bikes don't get fuses, they measure current draw and electronically cut out circuits it doesn't like - merc with fuses everywhere clearly have quite a bit the old fashioned way

I thought trailer recognition was some oddity (maybe a module) to tell the car something is plugged in so it can behave differently... I thought there was some places to code it on in some modules ( SAMs or maybe the cluster)

purdiemerc

Ok I have decided to use a relay switched by Fuse 133
My next problem is what is the best way/route to run a 50A 6mm (not 6 squar mm) cable from the boot back to the best place to take off that current, either with an inline fuse to the battery or via an existing fuse in the car to the battery.

Any help would be appreciated.

purdiemerc

BOTUS

the older cars pre-2008 get a large battery in the boot (hidden behind the back of the upright boot trim) - if its a later car with only the front battery - check, there is likely some mega cabling back where the battery was and if you can't find that there are two mega cables to feed the Rear SAM (but you don't want to interfere with those connections in a way that will get the SAM feed unreliable)

is this temporary or ? the lower panel gap of the tail light to boot lid leaves a convenient gap to push a cable past the wide flexible boot seal (high enough up rain is not an issue) its where I run a mains cable for my battery charger

if you want to wire to an external plug maybe try a gap from inside to outside via the rear of the tail light - from the sounds of your mega cable that's going to need help (bent the body around the tail light - the taillight has a 6mm sponge seal you can run small cables through tail no issue (at the bottom edge so rain doesn't come in)

purdiemerc

Thanks for the reply Botus
My car is a 2009 Model and does not have the extra Battery in the boot.
I have all the lining out of the boot to get the towbar fitted and the electrical lines tapped to the; turn indicators, stop lights and tail lights, installed to a hitch Box (basically a box of relays) the outputs of that box are then atteched to the 12 pin Caravan Plug on the car.
The High current cable will be used, via a seperate high current relay and Anderson connectors, to drive the Fridge in the Caravan while traveling.
So the high current cable in the car will be perminant.
I don't believe I have any left over Cables where the battery was in earlier cars, but I will take a good look later today.
I won't be trying to connect to the Rear SAM except to Power the Relay box from F145 "Trailer power supply" and F133 (just labeled as "Trailer coupling" in my Fuse Chart) to switch the seperate high current relay. F133 turns on and off when icnition is on and off. Relay activation current is abour 200mA so I think I am safe using it at that low current.
Any other advice you can give me on running the cable from the boot to the battery would be appreciated.

Thanks
Purdiemerc
Ralph Davies
Sydney
Australia

BOTUS

spare wheel well is plastic ? I think there is NO METAL so could drill through plastic and leave the real car normal

I don't know if there is a high volt bus panel in the back where the battery went / would go - like there is on the earlier cars... Probably ? either way the Rear SAM has two clip in mega 7mm diameter power cables - you could get a new terminal and make up your own wire, clip that in and then bolt the cars orig feed to your connector - you lift the red tang and a flat terminal pops off

purdiemerc

Thanks BOTUS
Very informative Picture.
I will have a look at a way of using that; 7mm Dia should handle an extra 30A. Do you know how those two wires are fed, i.e. which Pre Fuses are they attached to?

Thanks Again
Ralph

BOTUS

on my car they are from the battery control module that sits above the rear battery - I have not looked but I guess that (or something) is still there on the later cars

purdiemerc

Thanks Botus
There is nothing on my car where the extra battery was on older models, it goes across that space then up to the front of the car on the right side, probably to a pre-fuse unit ?
I have purchased an in line T connector that may fit the cable so I can tap off where it traverses where the second battery was in older cars.
I will let you know how that goes.

Thanks again
Ralph

purdiemerc

Hi Botus
I am having a look at the Connection to the SAM, But I can't get the red tag to move. How do you get it to pop off, pull from the top or the bottom ?
Also what type of Flat connector is under there, a picturre would be very helpfull.

Regards
Ralph

purdiemerc

Hi Botus
I am having a look at the Connection to the SAM, But I can't get the red tag to move. How do you get it to pop off, pull from the top or the bottom ?
Also what type of Flat connector is under there, a picturre would be very helpfull.

Regards
Ralph

BOTUS

in the picture above - look carefully, you can see the black bits on the side that lock the red bit in, the red bit hinges - so in that pic the lowest bit of the red thing lifts up hinging towards the yellow wires in black cloth tape - once over 90 degrees the metal tang of the big red wire can be wobbled out downwards

purdiemerc

Thanks Botus


That information is very useful; it is a bit hard to see that sort of detail with the SAM still in the Car.
I did loosen the SAM so I could move it backwards, to see more, but there is very little room to work there so I have now decided to use a T connector which attaches to a small area of bared cable to provide a connection. The area where the second battery was in older cars is readily accessible for that job and that thick cable goes across that area.
Link to the T connector is Below:-
https://order.ebay.com.au/ord/show?i...egname=11400#/

Regards

Ralph

BOTUS

you can spend a good two hours re pinning and thus untangling the mess that is Merc wiring to a SAM - its like every retard on the production line has a play and tries to make it worse and worse as the build progresses - a very impressive level of incompetence in play