hi i have a 1998 3.1 isuzu trooper and a 2003 swift conqueror .. my problem is when i connect caravan 12s plug to car everything works on 12v in caravan including fridge as it should but when i start engine it knocks everything off and nothing works in van ... i know it should switch everything off when engine runs but the fridge but it is also knocking the fridge off ..as anyone got any ideas...ps checked socket on car No6 pin and got power there...thanks....
If correctly wired the Fridge should not work from your car battery (there's a good chance that the battery would be flat in 10sec dead!), thus should only work when the vehicle engine is running and the alternator producing power.
Retired to France with the Vintage Camping Panzer (Hymer B594 2.5td 1993) and the boss. Since 1962 we have Static'd, Tented, Trailer-tented, Caravanned and now Motor-homing or rather Campingcarists :-).
Typically, a caravan fridge is rated at 120-140 watts on 12vdc. this gives a current draw from the car battery of between 10 and 11.6 amps. If the engine is not running, this would reduce the car battery to a gibbering wreck in about 4 hrs and would be incapable of starting a diesel engine in about 5 hrs.
Going back to first principles and, if the towbar installation is correctly wired, when the engine is running, the towing relay is energised from the engine alternator and provides a 12vdc supply from the car battery through the 12S plug to the fridge and the caravan battery charging circuit. When the engine stops, the alternator ceases to supply the relay with the energising 12vdc and the relay drops out. The supply from the car battery is then removed from the fridge and the caravan battery charging circuit.
If, as you say, after plugging in the 12S plug there is a 12vdc supply to the fridge with the car engine switched off but the 12vdc supply goes off when you start the engine, it would suggest that there is a relay wiring fault or a spurious earth return problem.
It must be appreciated that diagnosing this type of fault at a distance is extremely difficult. It is suggested that the relay connections are checked out as a starting point.
hi.. thanks for all the replies...checked all the relays first.. and found the habitation relay under the seating at the front of van next to the water heater was faulty replaced and working fine now... thanks again