If you checking for voltage yes, as you described red on one end of fuse holder and black on the chassis negative ground.I’m almost ashamed to ask this (as I should know the answer) but where exactly do you place the tips of the multimeter? Do you touch one lead, say the red lead, on one terminal of the fuse holder and the black/com lead on the other terminal of the fuse holder or to some other ‘earthing’ point?
I frequently read posts where the advice to diagnose a problem includes checking that the device is getting 12v at various points. It’s not always clear to me where the test meter leads should be placed.
Help my hab batteries are not charging
- Thread starter Just smiffy
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OP
OP
I’m almost ashamed to ask this (as I should know the answer) but where exactly do you place the tips of the multimeter? Do you touch one lead, say the red lead, on one terminal of the fuse holder and the black/com lead on the other terminal of the fuse holder or to some other ‘earthing’ point?
I frequently read posts where the advice to diagnose a problem includes checking that the device is getting 12v at various points. It’s not always clear to me where the test meter leads should be placed.
You're right, strictly speaking the voltage is a voltage between two points, in this case the D+ positive supply and the D+ negative return. However in a vehicle all the negative returns are connected together, and go through the chassis, so for most purposes any point on the chassis or bodywork will be OK.
If you're working in the engine area there's plenty of solid metal to act as a negative, but in the habitation area it can be a bit of a problem finding a negative. In the picture, next to the big B1 and B2 terminals there is a third big terminal which is the negative, and that would be an excellent point for the black probe.
If that's not available, then any nearby metal such as a bolt is worth a try. Check with a known positive supply to see if you get a good 12V reading, then you can use that point as a negative for any other measurements.
Thank you autorouter . This is precisely the detailed advice I required with regards to finding a negative point. Thanks too to all the other posters who offered advice and information.
Lenny HB
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Had a chat with Garry the CBE distribution unit is not receiving a D+ signal, the fuse was OK but he changed it anyway. He also said the fridge had never worked on 12v.
So he is now stripping the van down to try and find a D+ relay box and follow the D+ wiring.
So he is now stripping the van down to try and find a D+ relay box and follow the D+ wiring.
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Does he have satellite tv? D+ is generally used to signal engine start/dish lower. Maybe it's been redirected? 
Lenny HB
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Nope.Does he have satellite tv? D+ is generally used to signal engine start/dish lower. Maybe it's been redirected?
Do you know which DS box he has? Should be a connector in there somewhere for D+ in, (and maybe a free spade for D+ out)?
Lenny HB
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DS 300
i thought the same when i saw it
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Should be the block to the left of the relay. Top pin according to manual. Zoom in on photo, but can't see the cable.
On our van (2007 Hymer on Fiat) the fridge is linked to the vehicle battery by a fuse/fuses located down the side of the vehicle battery in the floor. We had them both burn out many years ago when travelling with the fridge on the auto setting. Had them replaced along with the fuse holders. One of the fuses was ( from memory 25 or 50 amp and the other much smaller one. Could these fuses be the reason why the fridge isn’t working off 12v? Since then wife has never trusted the use of the fridge, when travelling, on auto and so (wo)manually does it with a reminder note to switch off when we stop. After the fuses burnt out in wanting to find a reason, I found that the wires behind the lower (external) vent were not tightly clamped by the screws. Tightened up and no problems since.
Two on Tour
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Usually on the Sevel vans the base vehicle wiring is connected to the converter's wiring at the base of the driver's "B" post.
Our van has a CBE SRX250 relay fuse box at the bottom of the "B" that takes the D+ and then sends it through to our hab area.
It seems that the CBE DS300 uses a switched ignition feed to produce a simulated D+ for split charging and fridge relay operation , there is a manual for these units that may be useful in Resources , Manual for Motorhome Stuff , page 3
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This Here looks the same as your CBE DS300. The 2 pin Mate N Lok socket (Page 15) looks to be devoid of any cables. But maybe one is hiding!! I have a Trigano type DC300-TR and doesn't have the relay with the green dot. That's the battery parallel relay. Do you have R37 at the bottom left corner of the PCB (Page 16). For info my battery parallel relay is under the floor just behind the front seats under a black metal panel. Happy hunting
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OP
OP
Over the next few days I’ll check the wiring behind the fridge… I suspect charging the habs from the engine has never been working because my fridge has never worked on 12v but with 400w of solar and victron 100/30 my exide gels are usually fully charged in the pm, but it would be good if I can get it working.
I will continue to investigate when I have time from having a good time…
Could you make due with a ignition life feed? You could put a switch in it to disable it when not wanted. Thats how I turn on my b2b with a ignition life and switched as in when needed. I can’t find a D+ on a crafter 2. It works.
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Apologies for only half the info. That PCB has a black cover that has a vent grill.
stevewagner
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Has the resistor R37 been snipped?
OP
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The CBE DS300 unit that is fitted in this case does not need a D+ signal from the alternator only a switched ignition supply , ( to the red terminal J2 , next to the relay shown in the photo ) the DS300 then supplies a simulated D+ to enable relay operations for split charging, fridge etc. (I think it may use a volt sensing relay to do this )
He can’t find it, hence bypass the DS and run the ignition life directly.
Edit: Deleted post
OP
OP
It must have had a wire going to the cbe at sometime..? I can’t imagine the previous owners being on hook up all the time, but nothing surprises me….
I can’t find any evidence that there is or was a D+ coming in, later I’ll have a look at the back of the fridge and see if there’s a d+ and where it goes…
The wiring on this conversion is all behind panels or cupboards and spay foam insulation so impossible to trace wires…
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