Habitation 12V Electrics (1 Viewer)

[Bart]

Yes.
The relay is the normally closed variety and power from the alternator OPENS the contacts making the circuit dead.
As long as there is no power triggering the relay the contacts are closed.

ok ill try that after i check that its not for the fridge

 

[Stealaway]

Hey just happened to see this . Get it right man ...its @irnbru not @ironbru Check out the wiring now

I'd always assumed you couldn't spell ❤

 

[irnbru]

I'd always assumed you couldn't spell ❤

In the olden days it used to be Iron Brew but had to be changed 1n 1946 due to branding laws...it wasn't actually brewed...so irnbru became born..There ya go a wee history lesson

^{_{Subscribers  do not see these advertisements}}

 

[pappajohn]

ok ill try that after i check that its not for the fridge

Easiest way to check if its hab or fridge....
Take the wire off 87a and put it on 87....it won't blow anything.
If it's the hab relay you should have no power, now start the engine and you should have power.
If that works put the wire back on 87a then remove and insulate wire 86...it SHOULD be the earth but you can never tell which way it was wired hence insulate it.
If it makes no difference then it's the fridge relay

 

[hilldweller]

In the olden days it used to be Iron Brew but had to be changed 1n 1946 due to branding laws...it wasn't actually brewed...so irnbru became born..There ya go a wee history lesson

Never realised you were that old.

 

[irnbru]

Never realised you were that old.

Yep times move on but I think Im still young enough to be your daughter

^{_{Subscribers  do not see these advertisements}}

 

[hilldweller]

Yep times move on but I think Im still young enough to be your daughter

Don't try that on, two is more than enough.

 

[Bart]

ok so turns out the combined circuit board / fuse box has what looks like 2 relays attached to it ( im pretty sure they are soildered in place as i tried to remove one and it was stuck fast and did not want to yank to much and maybe damage the board
So i think ill leave it for today.

 

[irnbru]

Looks like that bottom pic just needs the lugs pulled out to remove. Similar to the wiring on vending machine circuit boards.

^{_{Subscribers  do not see these advertisements}}

 

[Bart]

Looks like that bottom pic just needs the lugs pulled out to remove. Similar to the wiring on vending machine circuit boards.

What lugs ? and to remove what the whole board ? or relay ? or wires ?

 

[Jaws]

Oh boy do I recognise THAT bloody board !
I have repaired four or five of them.
The 12v feed for the fridge is not man enough for the job and it damages the connector and circuit board.
If ever your fridge fails on 12v that will be the culprit .. The last one I did had burned the connector right off the board leaving a nice big hole !
I cut off the plug and soldered the wires to the remains of the circuitry ...

 

[Bart]

Oh boy do I recognise THAT bloody board !
I have repaired four or five of them.
The 12v feed for the fridge is not man enough for the job and it damages the connector and circuit board.
If ever your fridge fails on 12v that will be the culprit .. The last one I did had burned the connector right off the board leaving a nice big hole !
I cut off the plug and soldered the wires to the remains of the circuitry ...

Fk i'm glag i never run it on 12v then gas all the time , even when driving ... time to get the hard hat on for the incoming flak
Jaws you are just the person then , that relay at the bottom on the left the "HFV7" would you say that is the 12V relay i am after ? and if so is that soldered to said board ,, also how had is it to remove the board. as the fuse box seems on the front of it ,, that parts scares me from investigating it closer >>>
But im fed up at the same time with the likes of the water pump / lights going out at night when you start the MH.

^{_{Subscribers  do not see these advertisements}}

 

[Linda and Steph]

In the olden days it used to be Iron Brew but had to be changed 1n 1946 due to branding laws...it wasn't actually brewed...so irnbru became born..There ya go a wee history lesson

 

[pappajohn]

Looks like that bottom pic just needs the lugs pulled out to remove. Similar to the wiring on vending machine circuit boards.

Barts refering to the relays, not the multi connector.

 

[Bart]

Barts refering to the relays, not the multi connector.

Thats what i thought irnbru was refering to , the connector ,, good job i didn't start to yank the relay..

^{_{Subscribers  do not see these advertisements}}

 

[Bart]

just came across this when reading about why there is a relay to switch off the electrics in the habitation area when the engine is running :


"It must be able to power the internal 12 volt electrical system of the caravan, but turn everything off when the engine is running

This is achieved by another relay, this time installed in the caravan. It is often called “the habitation relay”. With the engine off, the relay allows electrical current from the car battery to power the caravan’s 12 volt internal services... the interior lights, 12 volt sockets etc. The incoming feed from the car goes to a relay. This relay is controlled by sensing the voltage on the circuit that powers the fridge. Remember we said that we only want to power the fridge when the engine is running so we would not flatten the car battery when the engine isn’t running so we switched the fridge circuit “on” with the ignition... well in the caravan, the habitation relay senses the fridge circuit being turned “on” and when it detects this, it turns “off” so turning off the power to the internal 12 volt services. Why should we want to do this? Well, there are good reasons. With the increasing complexity of car electrical systems and the fact that modern cars are now control led by computers, especially things like ABS, Engine ECU’s, Traction Control and Airbags in order to make sure these systems are not compromised by anything electrical in the caravan, the habitation relay turn all the caravan’s systems off with the exception of the fridge circuit and the caravan’s road lights. This is why the earth’s for these circuits are kept separate."



Maybe i should just leave it as is ........................

 

[Jaws]

Fk i'm glag i never run it on 12v then gas all the time , even when driving ... time to get the hard hat on for the incoming flak
Jaws you are just the person then , that relay at the bottom on the left the "HFV7" would you say that is the 12V relay i am after ? and if so is that soldered to said board ,, also how had is it to remove the board. as the fuse box seems on the front of it ,, that parts scares me from investigating it closer >>>
But im fed up at the same time with the likes of the water pump / lights going out at night when you start the MH.

Sorry I do not know mate.. I tend to look, fix, move on.. If I tried to remember what all the bits do I would be madder than I already am !!
To remove the board ( from memory ) is easy enough
Remove all the fuses and anything else that plugs in the front ( some have a blind plug on, one I did had a relay ) then unscrew the retaining screws and the board falls off.
Whilst it is 'electrically flakey' in some aspects , the board is pretty robust physically

 

[Bart]

Sorry I do not know mate.. I tend to look, fix, move on.. If I tried to remember what all the bits do I would be madder than I already am !!
To remove the board ( from memory ) is easy enough
Remove all the fuses and anything else that plugs in the front ( some have a blind plug on, one I did had a relay ) then unscrew the retaining screws and the board falls off.
Whilst it is 'electrically flakey' in some aspects , the board is pretty robust physically

Had the board out since posting that , and both relays are soldered to the board, after reading the above that i posted about the Airbags , ABS etc , i think ill just have to live with the way it is , as i know for sure i'm not gona attempt to de solder the relay from the board , then find out its not that relay

^{_{Subscribers  do not see these advertisements}}

 

[pappajohn]

Did you try the stand alone relay ?

 

[Bart]

Did you try the stand alone relay ?

With the stand alone relay unplugged the lights & sockets still worked ok with the engine OFF , then when i started the engine they lost power , so there was NO DIFFERENCE in the hab power with or without that relay plugged in so that must not be the relay , also after about 1-2 secs of starting the MH i can hear the relay on the Circuit board pictured above ( which is the main hab fuse panel ) clicking right at the same time the power gets cut to the hab area.
Which leads me to believe that this is the Hab relay

 

[pappajohn]

Certainly sounds like its one of the board relays.
If you could identify the power terminals (30 and 87) on the relay you could bridge them with a wire link soldered in.

^{_{Subscribers  do not see these advertisements}}

 

[Jaws]

Certainly sounds like its one of the board relays.
If you could identify the power terminals (30 and 87) on the relay you could bridge them with a wire link soldered in.

Certainly sounds like its one of the board relays.
Put it back together first.. sit in the back with a finger on a relay. Get someone to start the engine.
Should be able to feel the clonk of the switch over quite easily.. but be aware the switch over for the fridge is on that board too

Orrrr..
Put it back together and with just the hab electrics turned on check all the connections making a note of all those with a 12v feed
Start the engine and check them again
You are looking for one that goes live when the engine starts

The wire you are looking for is usually quite a thin one
If all you find is big thick wire that is the fridge circuit and not the one you are looking for... And if that is the only one see last but one paragraph below

When you suss out which one it is, cut it ( in a place that will allow you to join it back up or join a couple of wires to it that you can take off to a switch
Once you cut the wire, restart the engine and I bet all the rear will still be live..
However ............ You will also need to check the hab batteries are still charging from the engine
I somehow do not think they will be..

Sooo.. If you cut the wire and put a switch in it, you could hit the switch to turn the hab electrics on for a while, then once finished turn the switch back on to set the system back to normal ( as in no hab electrics with the engine running )

I wanted to be able to use the water pump when on the move so fitted an extra relay ( operated by the same wire that switches all the had electrics off ! ) to feed voltage to pump part of the system only..
It is a bit OTT for most folk though

One odd thing.. and something that leads me to think that just maybe the change over is not actually on that board.
All the ones I have worked on were fitted in Euro vans.. and NONE of them switched the hab electrics off on engine start up..
For all I know the ability is on the board but not used on the Euro vans..But I suspect it is not on there at all but somewhere else..
This is pure speculation though

PJ, looking at the top of the relay to the right, it is 'normally open' so it would not be that one mate
The realy in question must be a 'normally closed' jobby

 

[tonyidle]

just came across this when reading about why there is a relay to switch off the electrics in the habitation area when the engine is running :


"It must be able to power the internal 12 volt electrical system of the caravan, but turn everything off when the engine is running

This is achieved by another relay, this time installed in the caravan. It is often called “the habitation relay”. With the engine off, the relay allows electrical current from the car battery to power the caravan’s 12 volt internal services... the interior lights, 12 volt sockets etc. The incoming feed from the car goes to a relay. This relay is controlled by sensing the voltage on the circuit that powers the fridge. Remember we said that we only want to power the fridge when the engine is running so we would not flatten the car battery when the engine isn’t running so we switched the fridge circuit “on” with the ignition... well in the caravan, the habitation relay senses the fridge circuit being turned “on” and when it detects this, it turns “off” so turning off the power to the internal 12 volt services. Why should we want to do this? Well, there are good reasons. With the increasing complexity of car electrical systems and the fact that modern cars are now control led by computers, especially things like ABS, Engine ECU’s, Traction Control and Airbags in order to make sure these systems are not compromised by anything electrical in the caravan, the habitation relay turn all the caravan’s systems off with the exception of the fridge circuit and the caravan’s road lights. This is why the earth’s for these circuits are kept separate."



Maybe i should just leave it as is ........................

Just a load of words. Each and every item built into a car or added later has to conform to a specification that ensures that it won't interfere with the various ECU-controlled parts of the vehicle. Because meeting the spec requires examples of every added device are submitted for testing before approval is given, and such testing is very expensive, MH and caravan builders have chosen not to do so. Quite sensibly IMO. So the other option is to turn all unapproved items off.

OEM starter motors and horns produce horrendous electrical noise, have not been modified to meet the appropriate specification, and yet have been tested and do meet it. I defy anyone to come up with anything fitted to a motorhome that has the same effect on the vehicle electrics as those two items which leads me to believe that there is no downside to bypassing the hab cut-off relay.

In other words do as you wish - it will not affect your base vehicle electrics.

 

[Bart]

Fk i'm running out of places to look for this relay, what is that on the board beside the relay HFV7 , is that possibly another relay ?

^{_{Subscribers  do not see these advertisements}}

 

[Jaws]

Fk i'm running out of places to look for this relay, what is that on the board beside the relay HFV7 , is that possibly another relay ?

Possible but ...
Have a look under the board. Look at the pin configuration of the known relay and compare it to the mystery object .. i.e. 4 pins set at different orientation

 

[Jaws]

In all this I forgot what the base vehicle is..
If it is a Fiat have a look around the cab battery area.. Seems a fairly common place for the buggers..

 

[Bart]

Possible but ...
Have a look under the board. Look at the pin configuration of the known relay and compare it to the mystery object .. i.e. 4 pins set at different orientation

Not sure what you mean ?

In all this I forgot what the base vehicle is..
If it is a Fiat have a look around the cab battery area.. Seems a fairly common place for the buggers..

Yip it's an X250 Fiat . When I installed the new battery bank . I never noticed anything at the cab battery . Mind you I was unable to trace where the 5+ positive cables from the cab battery lead to.

^{_{Subscribers  do not see these advertisements}}

 

[Jaws]

Not sure what you mean ?

Under as in behind.. where all the solder joints are .. as in the other side of the board to the components ..