VW T5 Electrics Query. (1 Viewer)

[Clive 1939]

My son has just bought a converted 2007 2.5 T5. The interior has clearly been done professionally. However I have a couple of queries regarding the electrics.
It's fitted with a PMS3V, and a 110AH leisure battery. It has a 60A VSR (which we plan to upgrade to a 140A with 110A associated cabling next week). The leisure battery charges OK from the alternator with the engine running but the fuse has a habit of blowing (hence the upgrade).
The PMS3V appears to have been connected (as far as we can tell) as per the wiring schematic I downloaded from the internet.
With no external mains connected the lights come on, but so does the fridge which I think is wrong (it's a silent-running fridge that I think draws much less current than a normal domestic fridge?). However it seems wrong to me.
Also, the battery condition meter on the PMS3 does not register when the 'van' position is selected. Everything seems OK when connected to mains on-site
Grateful for any thoughts.

 

[tonyidle]

What is a VSR?

 

[Boringfrog]

What is a VSR?

Voltage Sensitive Relay.

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[Riverbankannie]

The fridge would have some power from the 12 volt system.
It will be used for the igniter and to power up the control board.
Normally it would be a 3 way fridge operating on 12 volts from the engine when the engine is running, from 240 v if connected to mains via EHU or on gas. Sometimes you have to manually switch between these three but many modern ones are automatic.

 

[Boringfrog]

The fridge would have some power from the 12 volt system.
It will be used for the igniter and to power up the control board.
Normally it would be a 3 way fridge operating on 12 volts from the engine when the engine is running, from 240 v if connected to mains via EHU or on gas. Sometimes you have to manually switch between these three but many modern ones are automatic.

Possibly a compressor fridge.

 

[Riverbankannie]

Possibly a compressor fridge.

Yes of course, maybe, but he said it was silent running so I made an assumption that was an absorption type.

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[autorouter]

There are three types of fridge/coolbox: compression, absorption and peltier. Compression are more efficient, but are a bit noisy - most home and commercial fridges and freezers are compression. Peltier are electric only, and are used for smaller coolboxes and medical supplies coolers. Absorption types are (almost) silent and are used in motorhomes, hotel rooms and boats.

An absorption fridge works by heating the coolant mixture, making it circulate round the piping, and cooling by a complicated process involving the different mixture components moving, vaporizing and condensing. Heat is supplied by a mains 240 volt heating element, a 12 volt heating element or by a small gas flame.

It is quite common for these fridges to have Automatic Energy Selection (AES), where a small electronic control board switches between mains, gas and 12 volt heating automatically. Typically it switches to 12 volts while the engine is running, then back to gas when it stops. If the mains is hooked up, it selects 240 volts and switches off the gas.

I'm not too sure what happens if the gas runs out or is switched off, but I imagine it might switch to 12 volt operation. Since the element takes quite a lot of power, it will flatten a 110 Ah battery in a few hours. It's OK for stopping for lunch at the roadside, or on the cross-channel shuttle, but in general 12 volt operation is to be avoided. On most British vans you can't run the fridge off the leisure battery, but on continental ones it's normal practice.

The OP did not mention gas. Maybe the gas to the fridge is turned off. Or if it's not been used for a long time, it takes a few minutes for the gas to purge the air out of the tubes and start the flame.

Another possibility is that the fridge is running as normal on gas. The fridge indicator LEDs and the interior light all run off 12 volts whatever the energy source, so maybe the OP is thinking these lights mean it's running the 12 volt heating element as well, when in fact it's running on gas.

The 12 volt heating element takes about 15 amps, so maybe the display showing the battery input/output amps will indicate if the heating element is actually in use, or if the gas is causing the cooling.

If the fridge is running on gas, the fridge 12 volt control board takes a tiny current, and the main power comes from the gas flame. This is the normal operation mode when not on mains hookup.

 

[autorouter]

The leisure battery charges OK from the alternator with the engine running but the fuse has a habit of blowing (hence the upgrade).

What is the fuse value? Does it blow at random or does it blow when some event occurs (eg starting the engine)?

 

[Clive 1939]

Many thanks to all for all your advice. The fridge is 12v only. The fridge light comes on without the mains being plugged in. But to be honest I'm not sure if that's just the 12v lamp in the interior of the fridge, or whether the fridge is actually powered up.
The fuse (30A) blowing is random. Interesting that your Suzuki suffers from the same thing!
I'm hoping that the upgrade to a 140A VSR + 110A (100A fused) cabling will cure that.
Any thoughts on why the PMSV3 battery condition indicator only comes on when the van is plugged into the mains? It should, surely, register the condition of the leisure battery(?).

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[gus-lopez]

at.
Any thoughts on why the PMSV3 battery condition indicator only comes on when the van is plugged into the mains? It should, surely, register the condition of the leisure battery(?).

i'm sure our friends is exactly the same. I always thought it was odd.

 

[TheCaller]

Do you really need to uprate the VSR? I wouldn't have though you would want to charge a 110AH battery at more that a continuous 30A & you already have a 60A VSR. If the habitation battery is a bit flat, I can well see that the alternator may try & push more than 30A towards it when first started up. It may be that the cables & the fuse need to be uprated a bit, but I doubt you would need to go beyond 60A.

I'm assuming in this that the fridge has it's own relay. If not, then the one fuse may be carrying both the battery charging current & the fridge current, in which case I'm not surprised it blows occasionally. A pain to have to remember, but turning the fridge off just before starting the van & then waiting for 5 mins before turning it back on again might stop the fuse blowing.

Given that the fridge is 12V only, I would expect it to work at all times unless turned off at the fridge itself. If it's wired correctly, the PMS3V will supply it with power from the leisure battery or from the alternator is the engine is running.

I'm another one who would expect the battery condition meter to be working - at least any time the battery selector switch is to VAN. That's when you need it. It doesn't tell you anything useful when on EHU with the charger on - other than the fact that the battery is being charged.