It’s strange how work seems to come in batches. For example, we don’t see a Merc-based ’van for months, then we get three in a week. The same applies to the type of work that comes in – recently, it was fridge month, starting with the fridge in KC, our own motorhome.
You might remember that last year, we were having problems with the motorhome fridge not cooling consistently. I just about fixed that by renewing the heat transfer paste and repositioning the temperature probe, but it turns out, it wasn’t working properly on 12V while we were driving.
This became obvious with the temperature monitor I added last year. I’d pre-cool the fridge on mains for 24 hours before going away, then load it up, but after about an hour’s drive, I found the internal temperature had risen quite a bit.
Checking the voltage to the fridge heater element showed that with the fridge switched off and the engine running, I was getting full battery voltage at the fridge connections, but as soon as I switched on the fridge, the voltage dropped to barely 11V.
The reasons are twofold. First, the routing of the supply wire is ridiculously long – it goes from the starter battery to the Sargent distribution unit behind the driver’s seat and from there to the fridge via a rather circuitous route, resulting in a very long length of wire.
Second, the feed from the battery to the Sargent unit supplies not only the fridge, but also the leisure battery charging, which takes some of the available current from the fridge supply (see: the best campervan leisure battery if you’re after one).
My solution was to put in a new 6mm CSA feed, directly from the starter battery to the fridge via a fuse and relay. This means the supply line to the fridge is much shorter and is not being shared by anything else. Now with the engine running and the fridge switched on, I’m reading almost full battery voltage. There is some slight voltage drop owing to the load of the heater element, but that’s normal. Our fridge now stays cool while we drive.
Issues with customers’ fridges have been mostly down to failing electronics, but I did encounter one with a similar problem to our own – a large voltage drop to the fridge when 12V was selected.
This vehicle was quite new, so I advised the customer to go back to the dealer for a fix. It’s one thing modifying my own ’van, but a different matter when it’s a customer’s nearly new vehicle!
Are you after an alternative to your ‘van’s fridge? Then take a look at our best cool box for a campervan guide, where we share both non-electric and 12V options for keeping food chilled when you’re on tour.
Image: Robert Paul van Beets / Alamy Stock Photo
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