Ever wondered about how something on your motorhome works, but couldn't ask because it seemed like one of those simple questions you should have known the answer to all along? Well, wonder no longer. Here you'll find the answer to some of those questions about your motorhome that have always been bugging you. We have worked through the alphabet, paying particular regard to safety issues.
Whether you are a novice or an old hand, there will be something here that you didn’t know before ...

K  IS FOR
KILOGRAMS
The current practice is to express a vehicle’s different weights in kilograms and 1kg is roughly equal to 2.2lb. Furthermore, 1000kg equals a tonne, sometimes called a metric ton. Unfortunately it takes more protracted arithmetical calculations to work out that 112lb equals one hundred- weight and 20 hundredweights equals a ton. Alternatively, a ton equals 2240lb.
Let’s take this further to see how a ‘British ton’ relates to a Metric ton (tonne). To convert a tonne to a traditional British ton, you multiply it by 0.9842. In other words a metric tonne is slightly less than a British ton to the tune of approximately. 15.8kg (about 34.8lb).
However, if you’re buying an American RV kilograms don’t figure at all. And, in the United States, a British ton (2240lb) is sometimes referred to as a ‘long ton’. Also in America, a ton is 2000lb – a further fact that might be of relevance to anyone importing an RV.

L  IS FOR
LIQUEFIED PETROLEUM GAS (LPG)
See also: Butane and Propane
Motorhomes use liquefied petroleum gas – butane or propane. Both gases turn to liquid under pressure but on release from the cylinder, change back to a gas. LPG cylinders should never be stored on their sides because the liquefied gas will then be directly against the valve. If a leak occurs the gas immediately expands to around 200 times its volume with the ensuing risk of an explosion.

LIGHTING
For those taking a vehicle abroad to use in countries where you have to drive on the right, the beam of the headlights has to be altered in order not to inconvenience oncoming drivers. Altering the beams is not a difficult task on older vehicles because part of the headlamp lenses can be covered with carefully cut adhesive tape. However, recent vehicles are often fitted with bull’s eye headlamp units – especially some of the A-class models. If you own one of these, remember to check what has to be done to the units before you take a trip abroad. And don’t leave this to the last minute; modifications are not always straightforward.

LOADING
All motorhome owners should take their fully laden vehicle to a weighbridge every now and again. A model’s maximum technically permitted laden mass (MTPLM) will be clearly stated on the vehicle’s date plate which is usually fitted inside the engine bay. So is the maximum permitted loading for the front and rear axles. First, you need to weigh the whole vehicle by driving it onto the weighing plate; then you take a reading with just the rear wheels on the plate. The worrying fact here is that a large number of motorhomes have an over-laden rear axle*, while others even exceed the MTPLM. Not only is this dangerous: it is also a criminal offence. *Note: It’s less common for the front axle loading limit to be exceeded.

M  IS FOR
MOUNTINGS
Where an A-class (or coachbuilt motorhome) has been built on a chassis, the mounting points need checking during an annual service. Fortunately it’s not common to experience problems, but it’s best to exercise vigilance here.

MICRO-SWITCHED WATER SYSTEM
In this type of water supply system, micro switches are fitted as part of taps and shower control assemblies. When the control is turned on, the switch operates to allow current to flow to the water pump. The disadvantage of a micro-switch system is that the switches sometime fail and have to be replaced. However, unlike the pressure switching system, micro-switches are not affected by a drop in voltage.

N  IS FOR
NUMBER PLATES
No longer is it a simple matter to order a replacement number plate. Telephone your local car parts supplier to be absolutely sure what is required before making the trip. You’ll have to take items such as the Vehicle Registration Document V5 and a driving licence (or similar proof of identity). Suppliers are regularly checked by inspectors, so don’t expect them to show leniency if you forget to bring one of the necessary bits of paperwork – nor will they alter the spacing between letters to spell out your nick-name!

O  IS FOR
OIL FILTER
Be scrupulously attentive to vehicle servicing, and remember that it’s pointless changing the engine oil if you don’t change the oil filter. Alternatively it is pointless changing the oil filter if you don’t also change the engine oil! Moreover, get a garage to stamp your service manual and to add the date and the mechanic’s signature. These things are all-important elements when you come to sell your motorhome.

P  IS FOR
PRESSURE SWITCH WATER SYSTEM
A pressure switched water system is an alternative to the micro-switch system and it’s the more popular system employed in motorhomes.
Most pressure switches are housed in the casing of a diaphragm pump and that’s where you’ll find a screw or turn wheel to alter its pressure sensitivity. Sometimes, however, a separate pressure switch is mounted in line in the water pipe itself.
Either way, the components detect a drop in pressure when a tap is opened and immediately allow current to flow to the water pump.
The main disadvantage of the system is that if one of the pipe connectors has a tiny leak or a tap has been left slightly open, a drop in pressure will occur which in turn will cause the switch to activate the pump. In addition, a pressure switch is susceptible to a drop in the voltage of the leisure battery, although this can usually be solved by adjusting the switch. In the case of an in-line device, adjustment is via a knurled knob on top of its casing.

PROPANE
Propane is the second of the two liquefied petroleum gases used in motorhomes. While it has a slightly lower calorific value than butane, it can be used at temperatures of -40°C.
The amount supplied in the cylinder is also slightly less than with butane, but because it can be used in all temperatures, many all-year motorhome owners use only propane.

Q  IS FOR
QUESTIONS
Even the most experienced motorcaravanner asks questions from time to time. That’s where we come in. Mail, fax, email, or phone your questions to us at Practical Motorhome and we’ll do our best to find the answers for you.

R  IS FOR
REVERSED POLARITY
In the UK, the ‘live’ wire of an electricity cable takes the electricity to the appliance, while the ‘return’ cable takes it back to earth. Reversed polarity arises when the electricity flows the ‘wrong’ way through the cables. Thus instead of it flowing up the live cable and out through the return it does the opposite.
As the on/off switches in many appliances are fitted in the live cable it means that although the appliance may appear to be switched off, it is actually alive.
For around ten years, this has not been the problem it once was since motorhome makers now fit double-pole switched RCDs and MCBs which have reduced the potential danger. On the Continent, however, reversed polarity is much more common. To overcome the problem many motorhome owners carry a short lead, in which the live and return cables are changed over, thereby ensuring that the polarity is correct when the electricity reaches the consumer unit.

S  IS FOR
SERVICE HISTORY
Most owners of vehicles are careful in keeping the service records for their vehicle up-to-date and stamped. Rather less impressive is the willingness to have a habitation service carried out. And the manufacturers don’t always help here. Many motorhomes are not supplied with a comprehensive owner’s manual with a service stamping page to record habitation work – that is a mistake because this kind of information is especially important when you come to sell a vehicle.

SEALS AND SEAMS
On van conversions and coachbuilt motorhomes alike, body-mounted items such as skylights, framed windows, refrigerator vents and so on are all potential leak points. Now and again their sealing needs checking and a fastidious owner will have them re-bedded on fresh sealant every five or six years.

SECURITY
The possible theft of any kind of vehicle is something owners should take seriously. Don’t rely merely on one security device. Consider buying items such as a wheel clamp, a removable steering wheel, a pedal box clamp, an electronic alarm (such as Strikeback), a tracking system, a safe, and other items with a view to appropriate protection.

SEATS
In an ideal world, a motorhome built with four beds would be fitted with four travel seats equipped with safety belts. In truth, matching the number of beds with the number of belted travel seats isn’t a legal requirement although one could argue that if you have to be belted in the back of the latest saloon cars, why have a different rule for motorhomes? Some vehicles are certainly built with sufficient belted travel seats for the intended number of occupants, but many are not.

T  IS FOR
TORQUE
Torque roughly refers to the muscle power of an engine. At low revs, diesels typically have more ‘torque’ than petrol engines, which is why they’re often used in motorhomes. Because of their greater torque, they are more easily able to propel a motorhome briskly from a standing start, and then to keep the momentum going. In contrast, petrol engines usually develop their highest torque characteristics at high revs, which means that they have to be revved much more, and you have to hold onto the gears longer, to get your motorhome moving swiftly. Partly for the same reason, diesel engines are more economical. When choosing a motorhome, always look at the torque figures as well as the power figures so you know you’ve got enough ‘shove’ to cope with steep hills and heavy loads.

TOWING
If you want to tow behind a motorhome you’re intending to purchase, you need to check first of all whether it’s possible to have a towing bracket fitted. Just because you see that a bracket is listed in a catalogue for, let’s say, a Fiat Scudo panel van doesn’t mean it could be fitted on your Fiat Scudo-based camper van.
After conversion to a motorhome, your base vehicle may have a water tank or two mounted under the floor and you often find that items such as these completely obscure some of the attachment points. On the other hand, light commercial vehicles do not come under the requirements of the European Directive 94/20/EC – now with legal status in the UK after an amendment to The Road Vehicle (Construction & Use) Regulations 1986. This makes it mandatory for any tow bracket fitted to a post-1 August 1998 light passenger vehicle (carrying a European Whole-Vehicle Type-Approval Certificate of Conformity) to be a type-approved towing bracket. However, light commercial vehicles (used as the base for all but a few motorhomes) are currently exempt from this requirement which means that they can be fitted with a bespoke bracket designed and fitted by an independent specialist – and with no type-approval authentication.
Needless to say, other towing issues like noseweight limits and the relative weights of the trailer and tow vehicle must all be heeded when towing behind a motorhome.

TYRES
Motorhome tyres will depreciate rapidly if a vehicle is laid-up for an extended period without being moved. In particular, it’s the side walls of the tyre which sustain early depreciation and in response, some manufacturers, for example, Michelin, offer a specially reinforced tyre to suit the specific pattern of use typical of motorhomes.

TRAIN WEIGHT
Train weight, or to give it the full title ‘gross train weight’ (GTW). There are a number of issues to bear in mind if you want to tow a trailer behind a motorhome – and this is one of them. A motorhome will have a GTW limit printed on its data plate and this refers to the maximum permitted weight of the entire outfit – that is, a loaded motorhome and loaded trailer combined – and that figure must not be exceeded.

U  IS FOR
USER PAYLOAD
The user payload is the weight that you may add to your motorcaravan before it exceeds its maximum technically permissible laden mass (MTPLM) – in other words, the amount of luggage and other items with which you can load it. The MTPLM is found by subtracting the mass in running order (MiRO) – the motorcaravan’s unladen mass – from its MTPLM.

UPHOLSTERY
Life is never straightforward, and anomalies abound. With regard to the upholstery in a touring caravan, models built on or after 1 March 1990 are legally required to have Combustion Modified (CM) foam. This matter was also mandatory in respect of domestic furniture in our homes. But not the upholstery in a motorhome. The seating in road-going vehicles comes under separate jurisdiction and there was no parallel requirement to install combustion modified foam in motorhomes in the regulation of 1 May, 1990.
In practice, some manufacturers install combustion modified foam as a matter of safety but it is probable that many motorhomes are not thus equipped.

V  IS FOR
VENTS
You will notice that there are many ventilators in a motorhome, including vents for a Dometic (or Electrolux) refrigerator, vents in the gas locker, vents in the floor under your cooker, and several other vents around the interior. These are all important and they shouldn’t be covered up. Some vents are there to allow an appliance to keep cool – as in the case of a refrigerator. Others are to provide a gas escape point – as in the floor vents under a gas appliance. All vents have an important part to play and have often been installed in order to comply with European Norms and British Standards.

W  IS FOR
WATER PUMPS
Most British-built motorhomes are equipped with a diaphragm pump which is self priming. However, a number of German motorhomes and a few UK-built motorhomes have a submersible pump. As a rule, submersible pumps are less robust than a diaphragm pump and if they fail they usually have to be thrown away and replaced. In contrast, diaphragm pumps can be repaired and suppliers of models such as the Shurflo, run a repair and service operation. Occasionally, motorhome owners report that their diaphragm pump is rather noisy and this is usually because it has been screwed down so tightly that its rubber feet are compressed. Then the board on which it is mounted starts to reverberate and acts as a sound amplifier. The remedial action is self explanatory.

X  IS FOR
A SHOW OF GRATITUDE
No we do not intend to blow a kiss to anyone who has read thus far. But we do hope you will keep this list of hints, tips and info in a handy place, and have learnt something you didn’t know already.

Y  IS FOR
YOUNG CONVERSIONSS
If you ever thought you might like to convert a panel van yourself but didn’t feel able to fit a high-top roof or to tackle an electrical system, Young Conversions can help you. This is one of a number of small-scale manufacturers which will part-build a motorhome to meet customer requirements on a new or pre-owned van. Or perhaps you don’t feel confident about buying a pre-owned van yourself and would worry about picking a dud? Young Conversions can even track down suitable pre-owned vans on your behalf. Then the company can either build a stylish conversion at a big cost saving, or do a part-conversion so you can finish off any sections you feel skilled enough to carry out yourself.

Z  IS FOR
ZETEC
A notable engine fitted into Ford cars. In the past, there were campervans built on Ford base vehicles such as the Ford Cortina – the Starcraft being a prime example. But to date, no-one has been bold enough to build a micro campervan on a Ford Fiesta with a Zetec engine. Or perhaps you know differently?

 • This A-Z was compiled with the assistance of our technical expert Doug King, and John Wickersham author of The Motorhome Manual, published by Haynes.