12v power to the caravan when towing

[alaintaylor]

We have had 14 months of not having a reliable fridge running on 12v and since we travel long distances this has become a real pain. It looks like the problem is insufficient power coming from the car to operate the car relay to power the fridge. When no auxillary electrical equipment is running on the car then it's OK (and of course it was always OK on test) but add a radiator fan, lights, a/c, etc and the available power drops to or below 13v - tripping the fridge supply relay in the car (and presume battery charging as well).

I'm now in the process of checking different relays and the car system. Has anyone had a similar experience and a cure? My car is a 2006 Volvo V70 T5, BUT only has a 60 amphr battery as standard. The fridge is a 77litre Dometic, so nothing outrageous. I'm still not ruling out a fault with the fridge but power checks point to the car problem.

The Belgium GP is coming up and desparately need my G&T (with ice) on arrival! (not to mention real English sausage of course)

Alan

 

[rosies]

Hello Alan , It sounds very much like the car relay operating your electrics for your caravan is tripping in/out earlier than you need . This type of relay is usually called a smart relay and " should " be adjustable so it only operates when the car engine is running . The relay has to be set above the 12v battery output but below the total alternator output ie between about 12.5volts and 13.5 volts . Ideally you want your smart relay to cut in ( power to caravan battery/fridge ) at around 13ish v and cut out ( no power to caravan battery/fridge ) around 12.5 volts , so you can see its quite a fine margin .

If you feel capable and confident to tackle this yourself then find the smart relay and check to see "if " its adjustable , if it is then you can proceed .

Either couple up your caravan electrics to your car or fit a test light to earth number 7 pin and caravan fridge pin 6 . this is on caravans post 1998 on the grey 12s socket . You should not get any power at all on pin 6 when the car is not running . Start you car engine and after a few seconds you should get 13v plus at number 6 pin , now switch you a/c on headlights on wipers on , and see if the power drops off , if it doesn't then put your heater fan on full , if it doesn't trip off then I think you have proved the car to be in order and you possibly have trouble with the caravan habitation relay situated inside the caravan . If the power does trip of at any of these points then adjust your smart relay until the relay does not trip the power off ( only adjust in small incriments ) Now check that the relay will now cut out when the ignition is switched off and don't forget that the power has to decay out of the system , this is easier to see if the caravan is coupled up and the fridge decays the power , even so it might still take a minute before it trips off . If it doesn't trip back off you will have turned the adjustment to far so readjust to suit . I must say its far easier to do than explain .

The only real harm you can do even if you do everything wrong , is to adjust the relay so it is open/operating the whole time thereby when coupled to the caravan the power to fridge would be on all the time flattening the car battery . In that case you have turned the adjustment the wrong way .

If you don't feel confident then just take your Volvo to a "good " caravan knowledgible auto electrician and they will adjust/repair/change the circuitry to suit your needs

I do hope any of this may help you along Alan , Cheers Steve .

ps ask again if you get any problems .

 

[rosies]

Hello Alan , It sounds very much like the car relay operating your electrics for your caravan is tripping in/out earlier than you need . This type of relay is usually called a smart relay and " should " be adjustable so it only operates when the car engine is running . The relay has to be set above the 12v battery output but below the total alternator output ie between about 12.5volts and 13.5 volts . Ideally you want your smart relay to cut in ( power to caravan battery/fridge ) at around 13ish v and cut out ( no power to caravan battery/fridge ) around 12.5 volts , so you can see its quite a fine margin .

If you feel capable and confident to tackle this yourself then find the smart relay and check to see "if " its adjustable , if it is then you can proceed .

Either couple up your caravan electrics to your car or fit a test light to earth number 7 pin and caravan fridge pin 6 . this is on caravans post 1998 on the grey 12s socket . You should not get any power at all on pin 6 when the car is not running . Start you car engine and after a few seconds you should get 13v plus at number 6 pin , now switch you a/c on headlights on wipers on , and see if the power drops off , if it doesn't then put your heater fan on full , if it doesn't trip off then I think you have proved the car to be in order and you possibly have trouble with the caravan habitation relay situated inside the caravan . If the power does trip of at any of these points then adjust your smart relay until the relay does not trip the power off ( only adjust in small incriments ) Now check that the relay will now cut out when the ignition is switched off and don't forget that the power has to decay out of the system , this is easier to see if the caravan is coupled up and the fridge decays the power , even so it might still take a minute before it trips off . If it doesn't trip back off you will have turned the adjustment to far so readjust to suit . I must say its far easier to do than explain .

The only real harm you can do even if you do everything wrong , is to adjust the relay so it is open/operating the whole time thereby when coupled to the caravan the power to fridge would be on all the time flattening the car battery . In that case you have turned the adjustment the wrong way .

If you don't feel confident then just take your Volvo to a "good " caravan knowledgible auto electrician and they will adjust/repair/change the circuitry to suit your needs

I do hope any of this may help you along Alan , Cheers Steve .

ps ask again if you get any problems .

Alan , to find out if your relay is adjustable , look into the ends and see if there is a small screw within , only turn this screw a maximum of 90 degrees one way , actually more like about 30 degrees max usually . always note how far and which direction you turned it as you can turn it the opposite way if it doesn't do the job .

Steve .

 

[alaintaylor]

Alan , to find out if your relay is adjustable , look into the ends and see if there is a small screw within , only turn this screw a maximum of 90 degrees one way , actually more like about 30 degrees max usually . always note how far and which direction you turned it as you can turn it the opposite way if it doesn't do the job .

Steve .

Thanks Steve - will try it this weekend.

Alan