can anyone pls help,when we connected the 12n plug to the van at the weekend to run the fridge,the engine was running on the car but in the van the fridge was clicking on and off ,at the same time the battery indicator needle would drop to zero then back to green,it just kept clicking on and off ,the van batt was connected ,i've never used 12n on a van b4 in 12 years of towing,the tow bar is new on a new sorrento so has been tested prior to use ,what am i doing wrong ?
12v/car/van electrics
- Thread starter vinny2
- Start date
vinny, the fridge supply is on pin 6 of the 12S with negative on pin 7. This supply also switches the "habitation" relay in the van which disconnectes the supply to the 12v system [ positive pin 4 with negative on pin 3] in the van and connects it to the van battery to charge it en route.
It is clear that the supply from the car to the fridge and habitation relay is dropping in and out. There is a voltage sensing relay in the car which senses when the engine is running and connects the fridge supply when it is. The relay has an adjustment screw and I think all that is required is for it to be adjusted so that it is firmly on when the car engine is running.
Ray
It is clear that the supply from the car to the fridge and habitation relay is dropping in and out. There is a voltage sensing relay in the car which senses when the engine is running and connects the fridge supply when it is. The relay has an adjustment screw and I think all that is required is for it to be adjusted so that it is firmly on when the car engine is running.
Ray
Vinny, the relay has been provided as part of the 12S installation of the towbar/electrics. The relay is normally fitted in one of the side panels of the boot but check with the towbar fitter. It should be adjusted so that the supply on pin 6, with negative on pin 7, is ON when the engine is running and a load equivalent to the fridge {i.e approx 8 amps}is connected. When I adjust them I also have the car headlights on as well.
What is happening with yours is that it has been set to fine so it operates when the engine is running but as soon as the fridge starts to draw current there is a small volts drop which causes the relay to drop out again and it continues to cycle in this way.
Its also worth noting that when it is set correctly and the engine is switched off that the relay can hang for 30 seconds or more as the voltage slowly drops. This has the effect of the van 12v electrics continuing to be isolated untill the relay drops out. This has confused people who are towing and stop for a quick break and go into the van and the internal lights do not work. If this is the case then unplug the 12S and van electrics will come back on.
As your towbar /electrics are new go back to the fitter and tell him your problem and to set the relay as I have indicated.
Ray
What is happening with yours is that it has been set to fine so it operates when the engine is running but as soon as the fridge starts to draw current there is a small volts drop which causes the relay to drop out again and it continues to cycle in this way.
Its also worth noting that when it is set correctly and the engine is switched off that the relay can hang for 30 seconds or more as the voltage slowly drops. This has the effect of the van 12v electrics continuing to be isolated untill the relay drops out. This has confused people who are towing and stop for a quick break and go into the van and the internal lights do not work. If this is the case then unplug the 12S and van electrics will come back on.
As your towbar /electrics are new go back to the fitter and tell him your problem and to set the relay as I have indicated.
Ray
ray thanks very much for all your information. I will contact towbar fitter and tell him what you said so that he can rectify it.. Once again thanks very much, it is much appreciated.
Vinny, I have also had loose connections on the relays that cause the same effect. They appear to operate but when the fridge starts to draw current the loose connection ( high resistance} causes a volts drop which drops the relay out. In any event a check of the relay is required. Ray
Hello Vinney
I agree with Ray c's advice, but I would add one further point. Even though most modern cars are fitted with alternators that produce some charging current at tick over, the supply might not be very 'strong' If the habitation relay is set so it just clicks on at tick over, as soon as it switches on the electrical load of the fridge might be enough to drop the supply voltage enough to cause the relay to turn off. As this disconnects the fridge load, the voltage rises again and the cycle may be repeated.
This is only likely to happen at tick over, and as soon as the engine revs are increased, the problem should disappear. If it continues when the engine revs are higher, then there is definitely a problem either with the wiring between the alternator and the relay or the fridge.
I agree with Ray c's advice, but I would add one further point. Even though most modern cars are fitted with alternators that produce some charging current at tick over, the supply might not be very 'strong' If the habitation relay is set so it just clicks on at tick over, as soon as it switches on the electrical load of the fridge might be enough to drop the supply voltage enough to cause the relay to turn off. As this disconnects the fridge load, the voltage rises again and the cycle may be repeated.
This is only likely to happen at tick over, and as soon as the engine revs are increased, the problem should disappear. If it continues when the engine revs are higher, then there is definitely a problem either with the wiring between the alternator and the relay or the fridge.
Ray,
Question for u after reading your comments on the 12S not giving power to the caravan internal lights. On a caravan where there is no maual switching the power fron cearavan to car etc, how can I wire a 12S extension lead to give power to the caravn internal light incase on long site stays the caravan battery going low on power. I have ithe 12s extension wired forpin 4 permanent live.
Question for u after reading your comments on the 12S not giving power to the caravan internal lights. On a caravan where there is no maual switching the power fron cearavan to car etc, how can I wire a 12S extension lead to give power to the caravn internal light incase on long site stays the caravan battery going low on power. I have ithe 12s extension wired forpin 4 permanent live.
I also have experience of the fridge/freezer switching on and off while the habitation reley fluctuates between interior lights and battery charge. The answer was to replace the car's automatic voltage sensing relay with a relay switched by a ignition supply which is not live during cranking, in my case, an auxillary socket in the boot area.
Al
Al
Hi Vinny, I think Ray is talking common sense and you shouhld follow his advice. One thing though, you say the car electrics are new and were tested but you do not say how old your caravan is and have the plugs wiring been checked. Before you do anything connect up and get someone to give the car a few revs whilst you check in the van as John L has made a point about. My last van never operated the fridge until the revs rose.
Gordon, I have responded to your other query regarding the permanent supply on pin 4. I do not want to confuse the issue by talking about habitation relays, fridge supplies etc.
If you have a handbook with a wiring diagram in it I would be pleased to look at it and could advise further.
Ray
If you have a handbook with a wiring diagram in it I would be pleased to look at it and could advise further.
Ray
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