Autotrail EMC Relay Question

[GeoffL]

I have electrical issues with my 2001 Autotrail Scout (Ducato based) that I suspect might be due to a duff EMC relay. AFAICT most UK motorhomes of this era were fitted with an "EMC Relay", which is a lateral thinking method of getting around the EU EMC regulations for all the habitation electrical kit in the motorhome. Basically, it seems that this relay is designed to shut down habitation 12v electrics when the engine is running to allow the manufacturers to treat the caravan side of a motorhome like a trailer caravan!

The symptoms in my case are:

1. The habitation 12v doesn't shut down when the engine is running (although this did happen when I first bought the van until one day I turned on the 12v switch when the engine was running).
2. The grey water tank full alarm sounds when driving (the handbook says the alarm shouldn't sound at that time).
3. There's a large voltage drop in the 12v habitation system when drawing only a few amps even though voltage at the battery terminals remains unchanged. For example, turning on 8A worth of lights drops the system voltage to around 10v, at which time the battery terminal voltage might be 12.4v.

I've attached a diagram of the control panel layout to help identify which version of 12v system I have. Can anyone tell me where this relay is fitted and whether I can fit a manual alternative so that I can run the engine to provide habitation electrics for short-term emergencies?


Thanks for looking, Geoff

 

[nabsim]

I cant help with a relay but my 2007 Geist does not auto switch anything. My control panel has a switch to turn 12v leisure bank on and off then I have a light in the cab to indicate that I am running on leisure batteries. I am reasonably sure this has been changed to do this as I don’t think manufacturer would have fitted an amber light in cab roof panel although I haven’t checked with any other Geist owners to be sure.

I can run the engine while switched to the leisure bank but haven’t tried to see if everything will still work although the water pump does so I expect it will. Step auto retracts anyway when engine starts but that is an inbuilt safety feature.

If it is any help a wiring diagram for a DT101 (Schaudt) panel may say what the switch connects to for switching power

 

[GeoffL]

Thanks. According to some info I found on the 'Net, most of the major UK converters fitted one of these relays while most of those from mainland Europe did not. My panel is a Sargent produced exclusively for Autotrail and for a limited period AFAICT.

FWIW, I found some info from another forum after posting my question that shows the relay fitted to a 2004 Apache -- it's mounted onto the underside of the panel, but it's a different panel to mine. I'm hoping that I'll find the same relay when I take my panel out of the furniture, that I can demonstrate that there's a voltage drop across the relay that increases with current, and that I can find a replacment relay. The info I found includes a bodge to add a switch to one of the wires on the primary side of the relay to disable the relay when open.

 

[nabsim]

There will be some with much greater electrical knowledge than me along before too long I would think, surprised none have already commented regarding a manual switch if nothing else