Caravan fridge problems – how to fix the most common faults

by | Jul 1, 2020 | Cooling and Heating, Articles, CBRV, CME, Electrical (general)

by Collyn Rivers

Travel Trailer Fridge Problems

Travel trailer fridge problems are due to poor ventilation, inadequate cable size and/or insufficient power to drive them. Here’s how to fix them.

Travel trailer fridge problems - fix them yourself

Pic: Original source currently unknown.

Q. My travel trailer fridge works fine whilst on 230 volts, but not on 12 volts when we free camp. How can I can tell for sure if the fridge is faulty?

A. You can be 100% sure if you remove the fridge. Then see how it performs standing alone in a garage at much the same temperature.

Poor installation

Q. A friend says you emphasise in your book (Caravan & Motorhome Electrics that most travel trailer fridge problems are due to faulty installation. How has this come about?

A: A probable 95% of travel trailer fridge problems are because they are poorly installed. There are two main types of travel trailer motorhome fridges: 12/230 volt compressor, and 12/230 volt/ LP gas (so-called) ‘three-way’ fridges. Both suffer from poor installation. Some RV makers and many self installers do not understand how fridges actually work.

Fridges do not make cold. They are simply pumps that moves heat from where it is not wanted – to where it does not matter. You must have a cool air inlet at their base. You also need to direct that cool air through the fridges cooling fins. Rising hot air must easily exit.

Ventilation is vital

Ventilation is totally vital for three-way fridges. This only too often insufficient. Some have none at all. Unless ventilation is provided as specified (and illustrated in Caravan & Motorhome Electrics) they have no chance of working correctly, on either electricity or gas. See below if the fridge works on gas and 230 volts, but not 12 volts.

Many travel trailers now have access to 230 volts, so they use this most of the time. Here, cable size can usually be relied on to be fine. Use much heavier cable if it runs on 12 volt solar/battery power. The required cable, however, is costly – so is rarely used. Current draw on 12 volts is very high. It is only feasible from a vehicle alternator, and short lunchtime stops from battery power.

Q. I know travel trailer fridge 12 volt fridge cable is usually too small. How heavy must it be?

A: This depends on the distance from the battery – it should not exceed two to three metres. Errors are caused by there being several ways of specifying cable size.

When specifying cable size, makers of electrical stuff either quote the cross-sectional area in square millimetres, in AWG or B&S. The latter are identical for all practical purposes. For most electric compressor fridges, the minimum is 4 mm² (AWG 10), but 6 mm² ( AWG 8) is preferable. Three-way fridges draw from 12-30 amps. These really need 8 mm² (AWG 7) unless the distance is less than two metres (when 6 mm² is fine).

Auto cable size

Q. I hear there is a problem with the auto cable sold in auto parts and hardware stores.

A. Auto cable is usually just fine. But, for reasons that defy sanity, auto cable makers use similar ‘numbers’ as above (e.g., 4 mm, 6 mm) to imply something totally different.

Auto cable ‘4 mm’ is not 4.0 mm² – it is the overall diameter of the cable including its insulation. That rating is the size hole you can push the cable through!

Worse, auto cable insulation thickness and type varies from maker to maker. Most 4 mm auto cable is anywhere from 1.8 mm²-2.0 mm². Most 6 mm auto cable is 4.6 mm². The reason why so many fridges are affected is because that 4 mm² and 6 mm² cable are the sizes most commonly specified.  Be aware that even if you ask for (say) 4 mm² cable what you almost always sold is 1.8-2.0 mm² auto cable. Many people fall into this trap as few vendors know there’s a difference. (The square mm size is, however, usually shown in the cable’s specification.)

Travel trailer fridge – current ratings

Q. My three-way travel trailer fridge draws 25 amps. It is connected to the tow vehicle battery by ten metres (total for twin conductor) of 35 amp cable – yet barely works. A friend has your Caravan & Motorhome Book (that has a lot about travel trailer fridge problems). He says the cable is much too small. How can this possibly be? It’s already three and a half times the necessary current rating!

A.  Current ‘rating’ is mostly misunderstood. It is not a current carrying recommendation but a fire rating that relates only to the current the cable can carry before its insulation begins to melt. The rating has absolutely nothing to with voltage drop. The most commonly used ’35-amp’ cable can be as small as 4 mm auto cable (1.8 mm²)! Ten metres of this introduces a massive three volts drop. That fridge will barely work at all. The minimum you need is 10 mm², over seven times the size.

You need to locate that battery in the travel trailer, charged from the alternator by a caravan-located dc-dc charger. See: dc-dc charging. Still use proper size cable. (You owe your friend, and that fridge, one considerable apology!)

About the author

Collyn Rivers is an ex motor industry research engineer who switched careers in mid-life to write and publish technically correct books in plain English. They cover the travel trailer, motorhome and solar areas.

The ‘overall’ ones are the Caravan & Motorhome Book, and the second edition Camper Trailer Book. Electrical issues are covered in Caravan & Motorhome Electrics, solar in Solar That Really Works (for cabins and RVs) and Solar Success (for home and property systems).

Collyn Rivers is a semi-retired automobile research engineer.  He is the author of seven books, five of which are about making RVs and solar work optimally.

Caravan and Motorhome Electrics

The essential handbook for anyone with an RV of any kind.  Everything you need to know to make the electrics in your rig work for you.

Cover of Caravan and Motorhome Books by Collyn Rivers

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Caravan & Motorhome Electrics.  Just ask.
ISBN: 978-0-6483190-8-5

Solar Success

Whether you’re building a new home or adding solar to an existing structure, this is the one book you can’t afford to be without.

eBook versions

Paperback version

Any bookshop, whether online or bricks and mortar, can order copies of Solar Success.  Just ask.
ISBN: 978-0-6487945-4-7

Why Caravans Roll Over
and how to prevent it

Explains in detail every aspect of tow vehicle and travel trailer stability. This is what you need to know to be safe on or off the road.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Why Caravans Roll Over.  Just ask.
ISBN: 978-0-6483190-6-1

Solar That Really Works!

Solar that Really Works! covers the design, installation and use of solar in cabins, camper trailers, travel trailers, fifth wheelers, campervans and motor homes.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Solar That Really Works!  Just ask.
ISBN: 978-0-6483190-3-0

The Caravan & Motorhome Book

The Caravan & Motorhome Book covers every conceivable aspect of campervan and motorhome usage. If you own a camper van or motor home, you'll want this book.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of The Caravan & Motorhome Book. Just ask.
ISBN: 978-0-6483190-5-4.

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Caravan and Motorhome Electrics

The essential handbook for anyone with an RV of any kind.  Everything you need to know to make the electrics in your rig work for you.

Cover of Caravan and Motorhome Books by Collyn Rivers

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Caravan & Motorhome Electrics.  Just ask.
ISBN: 978-0-6483190-8-5

Solar Success

Whether you’re building a new home or adding solar to an existing structure, this is the one book you can’t afford to be without.

eBook versions

Paperback version

Any bookshop, whether online or bricks and mortar, can order copies of Solar Success.  Just ask.
ISBN: 978-0-6487945-4-7

The Caravan & Motorhome Book

The Caravan & Motorhome Book covers every conceivable aspect of campervan and motorhome usage. If you own a camper van or motor home, you'll want this book.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of The Caravan & Motorhome Book. Just ask.
ISBN: 978-0-6483190-5-4.

Solar That Really Works!

Solar that Really Works! covers the design, installation and use of solar in cabins, camper trailers, travel trailers, fifth wheelers, campervans and motor homes.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Solar That Really Works!  Just ask.
ISBN: 978-0-6483190-3-0

Why Caravans Roll Over
and how to prevent it

Explains in detail every aspect of tow vehicle and travel trailer stability. This is what you need to know to be safe on or off the road.

eBook versions

Paperback version

The book retailers set their own prices which can vary substantially. We'll aim to keep a selection of the better prices above.

Any bookshop, whether online or bricks and mortar, can order copies of Why Caravans Roll Over.  Just ask.
ISBN: 978-0-6483190-6-1