12V system on auto sleeper

[trevskoda]

If i had bought a van with all that cr-p above it would be ripped out and sorted a more simple way, total garbage.

 

[r4dent]

It was fitted by a fully qualified competent workshop and signed off

Just had another thought.

a) The van originally had a 3 way;
b) this was removed and replaced by a 230v electric fridge;
c) this was later removed and replaced by another 3 way.

When "B" was done it would be a good idea to remove the 12v supply to the fridge to avoid having a live 12v wire connected to nothing which would be dangerous. One way of avoid the live 12v wire would be to disconnect the wire from the alternator or remove a fuse/ relay from the alternator end of the wiring.

When "C" was done the fitter would see the original fridge end of the 12v wire and use it, not knowing the other end had been disconnected from the supply

If this happened it would explain the current (see what I did there) situation.

 

[r4dent]

Some older fridges would run on gass when traveling but they should be switched off or to 12 v when traveling , big fire risk after an accident if gass fridge is running

Also a big fire risk when filling with LPG or fuel, which is why AES fridges have a delay between the ignition being switched off and the AES switching from 12v to gas.

 

[mariesnowgoose]

Also a big fire risk when filling with LPG or fuel, which is why AES fridges have a delay between the ignition being switched off and the AES switching from 12v to gas.

What's an AES fridge?

Scrub that, just looked it up, makes sense - "Automatic Energy Selection"

(I've always been a big hater of acronyms, especially when you're a bit of an ignoramus like wot I is )

 

[PatrickS]

lots of previous replies and some good info given

Now as far as the line goes

Something is not right as it is working in the opposite way it should as you are now aware. Ignoring the competence or otherwise of anyone who has worked on your motorhome, it kind of sounds as if a relay has been replaced and the connection made to the wrong terminal?

On your 1998 Motorhome, you almost certainly have an early Sargent wiring system, and the relay for the Fridge power from the Starter Battery will be under the bonnet - see the diagram below where I have put a Red box over the relevant bits

Wiring Diagram Swift Suntor_Sundance 2002 by David, on Flickr
This is described as a Swift Sundance wiring diagram but the same diagram is applicable to many British Motorhomes of this era, including I am sure the Autosleepers.

What MIGHT have happened is when the problem was being investigated, the normal relay - a standard 12V 4-pin relay - may have been replaced with a 5-pin relay? A perfectly acceptable thing to do, but it gives the chance to misconnect the output to the fridge and results in the fridge only getting 12V when the engine is off, and stopping getting the 12V when then engine is running. Precisely what you are describing and I can picture someone making that mistake quite easily - but I can't so easily picture them not realising there was a problem and then correcting it quite quickly.

For the technical bit how it works:

• A 4 Pin Relay has an single pin out - Pin 87 - which is "NO" (Normally Open) and this is as it says 'Normally Open' until the relay is activated, for example by the engine running. If the engine is off, Pin 87 is open and no power. If the relay goes faulty, it can be stuck open or it can be stuck closed. Neither of those sound like they apply to your problem.
• A 5 Pin Relay is like a 4 pin one but as well as having a Pin 87 "NO", it also has a Pin 87a "NC" (Normally Closed) connection.
  You will have power into the relay on Pin 30, which is the supply. Pin 87 is the normal output and same as the 4 Pin relay, it is connected to the supply on Pin 30 when the engine is running and is open when the engine is off. However the Pin 87a is the reverse - it is connected to the Pin 30 supply when the engine is OFF, and then is disconnected from the supply when the engine is ON.

The reason for the problem may or may not be as I describe it above, but it is the only logical reason that comes to mind without someone doing some very strange rewiring. Checking the relay is a good first step and you can pull out the relay from its holder and see if it has 4 or 5 pins to start with. (note you have 2 relays side by side and it will not be obvious which is which, so look at them both).
If 4 pins, something else. If 5 pins, check further.
If you click on this link - https://www.easycarelectrics.com/normally-open-and-normally-closed-relay-diagram-symbol/ - and scroll down you can see the pin layout of both the 4-pin and 5-pin relays

Wow thank you for the very detailed response. I might just have a go at looking into that once I’ve re-read your comment several times to fully understand it.

 

[merl]

In the case that David (Wildbus) mentioned the installer would have had to change the wiring at the relay base so if there's a cable connected to the 87a terminal then that's the issue.
Move the cable back to terminal 87.
Out of interest how do you know for sure that the fridge is working working 'backward' on 12V? ie it's getting 12v when the engine is NOT running and no 12v supply to the fridge when the engine IS running? I assume you're checking the thick power leads at the fridge with a multimeter?
Dont be fooled by the fridge interior light! This is on a different circuit and may well be powered 'backward' to the actual refrigeration circuit of the fridge.

 

[PatrickS]

Out of interest how do you know for sure that the fridge is working working 'backward' on 12V? ie it's getting 12v when the engine is NOT running and no 12v supply to the fridge when the engine IS running? I assume you're checking the thick power leads at the fridge with a multimeter?
Dont be fooled by the fridge interior light! This is on a different circuit and may well be powered 'backward' to the actual refrigeration circuit of the fridge.

I don't know for sure. The red light 12v switch lights up when the engine stops, and goes off when engine is running.
It all sounds very complicated so I will get an electrician to deal with it.

 

[colinm]

Offhand I can think of 2 reasons it is working as described.
Firstly it might be connected to the wrong battery.
Secondly the relay might be connected the wrong way round.
Either way a competent motorhome workshop should be able to easily sort it if electrics aren't your thing.

 

[guerdeval]

Well, I'm none the wiser after that little lot!

For what it's worth: our old Autosleeper (2003 VW Gatcombe) the 12v for the 3-way fridge is definitely only for use when driving.

When parked up it is either gas or 240v hookup, never 12 volt.

As its happens we have never bothered with the 12v when driving, we just leave the gas on

I am totally lost when it comes to the info on "cigarette lighters" in the "habitation area"??
Never owned a van that had a "cigarette lighter" anywhere other than in the driving cab, but that may be just our limited experience and number of vans owned (not many!)?

Oh boy, have you just opened a con of worms

 

[guerdeval]

Just had another thought.

a) The van originally had a 3 way;
b) this was removed and replaced by a 230v electric fridge;
c) this was later removed and replaced by another 3 way.

When "B" was done it would be a good idea to remove the 12v supply to the fridge to avoid having a live 12v wire connected to nothing which would be dangerous. One way of avoid the live 12v wire would be to disconnect the wire from the alternator or remove a fuse/ relay from the alternator end of the wiring.

When "C" was done the fitter would see the original fridge end of the 12v wire and use it, not knowing the other end had been disconnected from the supply

If this happened it would explain the current (see what I did there) situation.

I think she nB was done they’d have just snipped off the 12volt wire

 

[r4dent]

I think she nB was done they’d have just snipped off the 12volt wire

Not very safe, leaving a loose wire that was live with the engine turned on. Do you know if "B" was DIY or professional

What did they connect to when they did c ? Did the fitter insert a new wire (if they did it should be clearly visible outside near the old "clipped" wire. )