No fridge or battery charging while driving

kelbal

Hi guys,
I have a problem with my 12V charging system. With the engine running I'm getting 14V back as far as the supply terminals on the motorhome 12V distribution board, but the fridge won't work and the leisure battery won't charge - so this 14V isn't being used. They both work perfectly while plugged in to mains - so that system is fine, and I'm confident there's no battery/fridge issue at all. My suspicion is that the 12V distribution PCB is busted and needs to be replaced.
Another thing to note is that if I take out the 30A fuse for the fridge (on the 12V board), the fuse itself is intact but the plastic around it is scorched brown. I'm wondering if we contributed to the downfall of the board by continually turning the fridge on while driving when the fridge isn't cold. I think you're only supposed to operate it while driving if its already up (or should I say down) to temperature.
Anyway, I'm just looking for thoughts/suggestions as to whether it looks the board is definitely gone, and what to look for as to the cause in the first place. I can probably fit a new board myself, but am wary of it happening again. Here's some photos....

thanks

zambo

Hi
The current used by the fridge (assuming it is the gas/electric type)on dc is not influenced by the heat of the fridge as it only heats an element with no thermostat in the circuit.When on mains i assume it is running on ac and not on dc trough your controller.The only difference between ac and dc to the fridge is the ac usually has a stat in the circuit,both heat an element to warm the evaporator the same as the gas does.
Yours Zambo

*Kol*

Do your lights and water pump work still?

kelbal

Yes, the connections are all good for the leisure battery to give power to the lights & pump when we're parked up. If I charge the leisure battery via mains in advance of a trip its good for a few days without hookup. Its just the leisure battery charging and fridge when driving thats at issue.
Not too bothered about the fridge, but if the battery isn't charging when driving, thats a big big problem

niloc1951

It's probably a different version but you might find something useful HERE

Aidan_M_M

common on those to burn the heavy consumer fridges , I only did another one last week . Did you check the D+ line? That should be fused too , common enough problem.

kelbal

niloc1951 wrote: »

It's probably a different version but you might find something useful HERE

Niloc, its for a similar system to mine, but not exactly the same - might come in useful though. Thanks alot

kelbal

Aidan_M_M wrote: »

common on those to burn the heavy consumer fridges

So the fridge gets blown because of a damaged 12v distribution board?

Aidan_M_M wrote: »

Did you check the D+ line?

My wiring diagram has a D+ mentioned on it (I think its the solitary blue wire on the very right of the PCB, that look right??) - but it seems to indicate that this wire goes from the 12V board back to the fridge. I thought the D+ line went all the way to the alternator. I'll trace it and see where it goes to for myself

thanks

Aidan_M_M

d+ just means the alternator switched feed , the fridge and charger both need a signal . is there power in it with the engine on?

The fuse gets burnt , as does the holder , because it;s a bad design of fuse holder for the current it's carrying .

kelbal

Aidan_M_M wrote: »

d+ just means the alternator switched feed , the fridge and charger both need a signal .

But this D+ is a wire that goes direct from the 12V board to the alternator?

Aidan_M_M wrote: »

is there power in it with the engine on?

The lights and water pump work fine - even when the engine is running (not that that's something I'd be regularly doing)

kelbal

kelbal wrote: »

But this D+ is a wire that goes direct from the 12V board to the alternator?

The regulator is the X-fighter looking thing with 2 screws. Bosch type alternator. That's where the brushes live too.

B+ goes to the dash battery light in the instrument cluster or maybe to a computer on a vehicle that has those comtraptions.

Are you charging your battery on a mains charger?

30A fuse for a 10A fridge . Is it 4mm² cable? Big fridge?

D+ is common to both circuits. It's wired through the Alternator -> Dash light -> Split charge relay coil -> Fridge relay coil -> Ground.

Relay coils can burn up over time. The one that doesn't click with your finger on the back is a suspect.

The brown crusty stuff on the connections are usually galvanic corrosion, electrolysis. Burnt makes the insulation crispy and looks sooty black. Either way clean them where you can.

For what it's worth it could be easier and better rewire both circuits yourself on shiney new uprated cable and improve your alternator charge and fridge performance.

As a matter of course if you have access to the 12V fridge connections a target of opportunity would be to test the fridge direct to battery to rule out a broken fridge. It'll spark if you forget to turn the fridge off while wiring.

zambo

Sir Liamalot wrote: »

D+ is common to both circuits. It's wired through the Alternator -> Dash light -> Split charge relay coil -> Fridge relay coil -> Ground.



g.

Hi
As I remember it the right hand of that circuit should be 'live'.when the alternator is not running there is no voltage on d and current flows back through

the dash lamp and it lights.when the alt is running there is 12v both sides of the lamp so it goes out
Yours zambo

zambo

Sir Liamalot wrote: »

D+ is common to both circuits. It's wired through the Alternator -> Dash light -> Split charge relay coil -> Fridge relay coil -> Ground.



g.

Hi
As I remember it the right hand of that circuit should be 'live'.when the alternator is not running there is no voltage on d and current flows back through

the dash lamp and it lights.when the alt is running there is 12v both sides of the lamp so it goes out
Yours zambo

zambo

Sir Liamalot wrote: »

D+ is common to both circuits. It's wired through the Alternator -> Dash light -> Split charge relay coil -> Fridge relay coil -> Ground.



g.

Hi
As I remember it the right hand of that circuit should be 'live'.when the alternator is not running there is no voltage on d and current flows back through

the dash lamp and it lights.when the alt is running there is 12v both sides of the lamp so it goes out
Yours zambo

zambo

Sir Liamalot wrote: »

D+ is common to both circuits. It's wired through the Alternator -> Dash light -> Split charge relay coil -> Fridge relay coil -> Ground.



g.

Hi
As I remember it the right hand of that circuit should be 'live'.when the alternator is not running there is no voltage on d and current flows back through

the dash lamp and it lights.when the alt is running there is 12v both sides of the lamp so it goes out
Yours zambo

kelbal

Hi Guys,
I found a document relating to my electrical system on the web, there's a screenshot of the 12V wiring below. Connection 1 on port 14 is labelled as "Signal entry, key from engine starting" - thats a rough translation from French. I traced this cable from the 12V board all the way back to a connection block behind the steering while, and the cable is intact as I did the continuity test on my multimeter.
With my multimeter spanning between this "Signal entry, key from engine starting" and the common neutral (-B2) on the 12V board, I started the engine and I'm seeing nothing at all (have it set to detect DC voltage in the 12V range). I'm assuming this connection should be giving around 12V with the engine running? Does this imply that I've a wiring/connection problem up in the cab somewhere?
Thanks

Aidan_M_M

So in other words, No, you DON'T have a D+ signal. Check where it's attached to the alternator wire.

kelbal

Aidan_M_M wrote: »

So in other words, No, you DON'T have a D+ signal. Check where it's attached to the alternator wire.

Yeah, that was a long winded way of saying I don't have a D➕!!
I'm not at home now to check, but would this typically be fused in the main van fuse block? Would be the next place to check if so
Thanks

kelbal

Sir Liamalot wrote: »

Are you charging your battery on a mains charger?

30A fuse for a 10A fridge . Is it 4mm² cable? Big fridge?

Thanks for your mail SirLiam. Yes, the inbuilt mains charger in the motorhome is how I'm charging it before I head on a trip.
It's a tall fridge/freezer, not an under-counter job.

I've traced the D+ back to a connection behind the steering wheel. There's a Relay in the fuse box that seems to be for it. The Ford manual say the relay is for "Battery Saver / D+ - only comes on with engine running". I'll have a go replacing that.

kelbal

hi guys, in my wire tracing I've come across 2 relays so far, one as part of the main fuse box behind the glove box, its a Ford part like this...


and I've also found a relay behind the dash,which the D+ cable goes directly to. This relay also handles the 12V cigarette socket (which works), it looks like this...


Do Relays commonly fail? Is there a way I can test them to see if they've failed? I'm wondering whether to just replace these in an attempt to get my D+ connection established again - or if I should keep trying to trace a break in connection somewhere

thanks

zambo

It may be wired to take power from the lighter socket and pass it on to the fridge.does the relay click when engine comes up to speed/charge light goes off.Check for power on terminal opposite one going to lighter socket with charge light on and off and report back.
Yours Zambo

kelbal

zambo wrote: »

It may be wired to take power from the lighter socket and pass it on to the fridge....

The lighter socket works all the time (even when engine off), and still does - so I don't think its wired to pull its power directly from there.

On further investigation and tracing wires (it's very difficult to get at some of them), I've come across a little device which I have no idea what it is. There seems to be a missing wire from it (which may be hopeful), is it some sort of fuse?......



thanks

kelbal

Finally - got it sorted . Through all my tracing I found a clamping together of 2 wires that is a bit loose. Wiggle it a bit, and the connection is there again. Thanks so much guys for your advice in pointing me in the right direction.

p.s - I'd still like to know what the device above is!! There's circuitry on the back of the lid of the device, with what looks like a covered resistor or something. Dead curious to know what it is.

thanks again.

Aidan_M_M

it's the buzzer for the step.

kelbal

Aidan_M_M wrote: »

it's the buzzer for the step.

thanks. Never heard it going - is it a warning buzzer to say the step is down when I'm driving off?

Field east

Hi Kelbal,
Must hav given u great satisfaction when u found cause. When I saw relays mentioned , I thought that it might b useful to share my two experiences with relays.

(1) when I had a problem with passing the CRW test re Lambda, HC and CO levels I was advised to get the carb checked . I got that done , stuck it back on and when I went to start the engine there was not a sound. Got hold of my local mechanic - a vintage vehicle enthuasist . He disconnected a relay related to the spark distributed system , sprayed WD40 into it, worked the connection in and out a few times and eng started with no problem after that. The mechanic put a good amount of electrical tape around the relay to help keep it moisture free
(2) was suspicious two months after the above that fridge was not working well while driving and fridge in battery mode. I looked at El circuit in MH operating manual and noticed that there was a relay unit. Found it beside the battery. Did the WD40 job on it and is working perfectly since.
Am not a trained mechanic or electrician so if the above is 'not good practice' would appreciate any comments to put us all straight.

kelbal

Field east wrote: »

Hi Kelbal,
Must hav given u great satisfaction when u found cause. When I saw relays mentioned , I thought that it might b useful to share my two experiences with relays.

(1) when I had a problem with passing the CRW test re Lambda, HC and CO levels I was advised to get the carb checked . I got that done , stuck it back on and when I went to start the engine there was not a sound. Got hold of my local mechanic - a vintage vehicle enthuasist . He disconnected a relay related to the spark distributed system , sprayed WD40 into it, worked the connection in and out a few times and eng started with no problem after that. The mechanic put a good amount of electrical tape around the relay to help keep it moisture free
(2) was suspicious two months after the above that fridge was not working well while driving and fridge in battery mode. I looked at El circuit in MH operating manual and noticed that there was a relay unit. Found it beside the battery. Did the WD40 job on it and is working perfectly since.
Am not a trained mechanic or electrician so if the above is 'not good practice' would appreciate any comments to put us all straight.

thanks, good to know

Sir Liamalot

Sir Liamalot wrote: »

B+ goes to the dash battery light in the instrument cluster or maybe to a computer on a vehicle that has those comtraptions.

Correction: D+ goes to the dash battery light in the instrument cluster (through a diode in the fuse box hence the "D" methinks).

B+ goes to starter and battery.

kelbal wrote: »

Do Relays commonly fail?

Yes but it's rare. They're rated for 100, 000's operations.

kelbal wrote: »

Is there a way I can test them to see if they've failed?

Send 12v to ground through the coil and see if you get continuity across the load terminals. Or just see if it clicks if the ciruit is working.

kelbal wrote: »

T I've come across a little device which I have no idea what it is. There seems to be a missing wire from it

Hard to see but looks like one of the contacts has become desoldered and there's too much stripped insulation.

kelbal wrote: »

Finally - got it sorted . Through all my tracing I found a clamping together of 2 wires that is a bit loose. Wiggle it a bit, and the connection is there again.

Kudos. Maybe worth re-terminating it again, in case the crimp is failing...or just compress the spade connector to increase the grab.

Field east wrote: »

The mechanic put a good amount of electrical tape around the relay to help keep it moisture free

Electrical tape more often than not has the adverse effect; it retains water. Heat shrink is more appropriate. Or a holder. Water isn't generally the problem apart from corrosion implications, saturation causing water to bridge contacts is.

Field east wrote: »

Found it beside the battery. Did the WD40 job on it and is working perfectly since.
Am not a trained mechanic or electrician so if the above is 'not good practice' would appreciate any comments to put us all straight.

Sounds like a mechanical fail. If it works it works. I dunno if petroleum products are bad for the coil enamel...air compressor, a good beating or contact cleaner would probably do as well.