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Ducati750cc · 22nd May 2021, 10:50

Though this is not directly to do with wiring a 12 and 12s into a 13, simple if you take your time, are methodical and get a diagram.

Some things to be aware of, some modern vans have ATC so to future proof, wire up for this also.

Many van owners complain of the fridge not cooling sufficiently on 12v, nor the van battery not being kept charged on long journeys.

The usual cause is volt drop between the car and van due to thin cabling, in extreme instances, around 14v can be seen at the battery, engine running, but only 10-11v at the fridge terminal block itself and at these voltages the fridge won't cool nor the battery charge.

If you tow a van and find this, there are a couple of work rounds, one is to utilise spare pins in the 13 pin socket to double up the + and - cables, or wire a dedicated supply back to the battery + and a good car chassis - ,you should find details for these on the net and possibly caravan forums.

One other one thing that won't apply to 75's though, but will to many new cars, I've put this in because there may be 75 owners who tow with their 75 and a newer car, is the problem with smart alternators in that some, if not most, reduce the charge rate from the normal approx 14v to around 11v when the car battery is fully charged, to save fuel, kicking back in when the car battery voltage drops to a certain limit.

The outcome of this is that when the voltage is at 11v or thereabouts, the fridge doesn't cool, nor the van battery charge, there are work rounds to this, one simply disconnecting the alternator sensing wire at the battery where fitted, the other is by getting the dealer to alter the alternator control criteria, for a fee.

22nd May 2021, 10:50	#7
Ducati750cc Loves to post Rover75 tourer Join Date: Jun 2018 Location: Ashton Posts: 428 Thanks: 121 Thanked 206 Times in 145 Posts	Though this is not directly to do with wiring a 12 and 12s into a 13, simple if you take your time, are methodical and get a diagram. Some things to be aware of, some modern vans have ATC so to future proof, wire up for this also. Many van owners complain of the fridge not cooling sufficiently on 12v, nor the van battery not being kept charged on long journeys. The usual cause is volt drop between the car and van due to thin cabling, in extreme instances, around 14v can be seen at the battery, engine running, but only 10-11v at the fridge terminal block itself and at these voltages the fridge won't cool nor the battery charge. If you tow a van and find this, there are a couple of work rounds, one is to utilise spare pins in the 13 pin socket to double up the + and - cables, or wire a dedicated supply back to the battery + and a good car chassis - ,you should find details for these on the net and possibly caravan forums. One other one thing that won't apply to 75's though, but will to many new cars, I've put this in because there may be 75 owners who tow with their 75 and a newer car, is the problem with smart alternators in that some, if not most, reduce the charge rate from the normal approx 14v to around 11v when the car battery is fully charged, to save fuel, kicking back in when the car battery voltage drops to a certain limit. The outcome of this is that when the voltage is at 11v or thereabouts, the fridge doesn't cool, nor the van battery charge, there are work rounds to this, one simply disconnecting the alternator sensing wire at the battery where fitted, the other is by getting the dealer to alter the alternator control criteria, for a fee. __________________ Common sense isn't a gift, it's a punishment because you have to deal with everyone who doesn't have it.