Habitation 12 volt on the move

[HIGHPRYCE]

I am new to this posting, and quite new to motorhoming. In the July issue of MMM page 254 the response to Neil Bakers e-mail about his lights and pump not working when his engine was running, was a lot of stuff about electro-magnetic emissions which I didn't understand, and a statement that 'the van electrical system is automatically isolated when the engine is running.' My question is: is this automatic isolation something that should happen on all motorhomes? Because it dose not on my 2006 Carthago Chic, on an Iveco base. As the reason given was because of the possability of interfearing with the engine management, ABS braking or stability control, I feel a little concerned. Any advice would be apreciated.

[Brian Kirby]

I think you can rest secure that if no such interlock was installed by the maker, it is not needed, and the safety systems will be unaffected by the habitation 12V electrics.

[Clive]

This interlock is a cheap get out by the motorhome manufacturers to satisfy the EMC requirements applicable to motor vehicles. Ideally they should either test the converted vehicle for compliance to the directive or alternatively compile a technical file which demonstrates why the additional wiring and components associated with the habitation equipment will not compromise the correct operation of the vehicle electrics when subjected to strong radio frequency radiation over a range of frequencies. Some vehicle manufacturers are happy to permit the basic connections, (Alternator B+, D+, Key switch+ etc) to be accesed at prescribed locations providing the new wiring is not run close or parallel to existing vehicle wiring. Other are not. Its a minefield for small converters and a pain in the backside to those of us who have this interlock. I don,t (now)!! EMC test chanbers are used by vehicle manufacturers and testing takes typically 2 to 3 days. A car size chamber cost £1000 per day to hire 5 years ago when I was involved in such testing. A lorry size chamber will be that much more expensive. The Technical file is by far the cheapest route but you do need an expert in the know to compile it.