Below is a diagram of a typical chassis used on older caravans (B&B design) from the 1950's - 1980 when it was replaced with the Al-Ko chassis design.
On a professional service, wheel nuts are replaced. It is recommended that you do the same. They cost around £5 and up to £12 for marine grade ones. They are available from car shops such as Halfords and websites such as eBay. You should also tighten up the wheel nuts to the recommended torque setting for your particular caravan. The torque settings are typically 120nm for steel wheels and 85nm for alloy wheels. They should be tightened to the relevant settings before each journey. Bear in mind they may vary for older models (1920's-1950's), but the figures quoted above apply to most caravans. Wheel nuts should be tightened in sequence: North, South, East, West (top, bottom, right, left) to ensure that the correct tightness is attained.
Most importantly, check the condition of the tyres. Caravans stand for long periods and tyres deteriorate much quicker than those on cars. Storing your caravan on grass will damage them over time - the constant wetting of the tyres with morning dew and drying out will cause the rubber to break down - which could lead to a blowout on the road. If you have to store your caravan on grass, then placing thin pieces of wood under the tyres is a cheap preventative measure to stop this from happening. Also, caravan tyres are very prone to flat spots. Check the sidewalls for signs of deterioration. ***NOTE: Check BOTH sides of the tyre, not just the visible side. You may have to take the wheel off to do this*** Caravan tyres should be replaced at least every six years, if not more frequently. While servicing, check tyre pressures and inflate as necessary.
3. 12N and 12S sockets COST: free DIFFICULTY: 1, Easy
This check is quite simple. Connect the caravan 12N socket (Black socket) to your car socket and test that the road lights are working. You can then test the 12S socket (Grey socket) but again attaching it to your car socket and running a 12v appliance. If your caravan doesn't have a 12v system, then it won't have a grey 12S socket. Caravans that don't have a 12S socket yet still have a 12v system will have a 12v system allocation on the black socket which is pin 2. This is only so that the car's battery can be used to power the caravan's own 12v system. Should you find any issues, be sure to clean the socket pins, as these often get dirty and stop working if dirt is allowed to build up. If this doesn't solve the issues, you can open up the sockets and check that all of the wires are connected properly, see diagram below. Terminals are numbered 1-7, clockwise with 1 being the top pin and 7 being the middle pin. In 1999 the pin allocation on the 12S socket changed, most vintage caravans will have the pin allocation as per the diagram below, but your caravan may have been changed after 1999, but this is unlikely. It is worth cleaning the terminals of the sockets using pipe cleaners and light sandpaper. This is optional, but will help reduce corrosion. A little light oil such as WD40 will act as a good cleaner for the terminal contacts.
4. Damp Check COST: around £25 for meter DIFFICULTY: 1, Easy
Damp checking is not compulsory on your own service, but may provide helpful for preventing damp damage spreading. If water ingress is spotted early enough, it can be repaired without having to replace any wallboarding. Damp areas can be obvious if they are in their later stages but in the early stages of damp when it is easily treatable, it can be harder to detect. For this reason I can recommend purchasing a damp meter from online websites such as eBay and caravan dealers for around £25. These meters will give you a reading and visual indication of damp levels. You should test the areas shown below:
5. Gas System COST: varies for replacement parts DIFFICULTY: 2, Moderate
All caravans no matter what their age will have a gas system. The trouble is that UK safety standards are altered frequently so you have to ensure that your classic caravan conforms to the current safety standards that are a legal requirement. There are only two types of LPG (Liquid Petroleum Gas) used in caravans: Butane (blue coloured bottle) and Propane (orange/red coloured bottle). It is up to you which type you use, there are pros and cons for both, but basically, Butane is better suited to summer caravanning and Propane is better suited to winter caravanning. But if you have one or the other, don't feel as if you have to change them during different touring seasons as the differences are only minor. Each type requires it's own type of gas regulator which should be the same colour as the gas bottle.
These are the devices that fit on the gas bottle and are connected to a pipe that takes the gas to the appliances in the caravan. It is vital that you have the correct regulator.
After the regulator, the gas is supplied via a metre or so length of rubber pipe to a solid metal mounting point, usually located at floor level on the exterior (or front locker) of the caravan. This rubber pipe MUST be replaced every four years and replaced more frequently should you find it to be cracked or worn. Rubber gas piping is available from all caravan dealers for around £1.50 per metre. Modern piping is supplied with a date stamped on it, so should the existing pipe have no date on it or be more than four years old, replace it. You have two choices, high pressure piping or low pressure piping. It doesn't necessarily matter which, but I would suggest high pressure pipe.
To replace the pipe, TURN OFF THE GAS BOTTLE FIRST and disconnect the regulator using a regulator spanner which are available from camping and caravan shops for less than £5. These are specially suited to gas bottle regulators and are the only way to disconnect the gas bottle from the regulator. Loosen the jubilee clip with a flat blade screwdriver and give the pipe a little encouragement to come off. Do the same at the end that the pipe is connected to the caravan's metal pipework. Then, slot in the new pipe onto the points which the old pipe was removed. This may be difficult at first so you can hold the pipe in boiling water to let it expand, thus making it easier to slide on. Tighten the jubilee clips back on. You can then reattach the regulator to the gas bottle and ensuring that the regulator and pipework are tightened up, can test the gas system out.
This is an opportunity to test the system out, especially for holes, leaks and damage. On a caravan dealer service, the workshop will pressure test the system to show any leaks or holes. If you do not have the facilities to do this, but don't worry; you can still carry out this check. Simply connect your gas bottle and light one burner on the stove inside the caravan. The flame should be a strong blue colour, any orange/yellow tips to the flame are a result of oxygen in the system, this means that there is air in the system and pipes may need replacing. It is acceptable for some light orange/yellow tips, but if the majority of the flame is orange/yellow, then there is a problem. Blockages will also be indicated by gaps in the flame. As the flame comes out of the holes in the burner, if some are missing or the flame is very low in it's full setting then there may be a blockage in the system. Should you find any problems, don't hesitate to contact either a caravan dealer or a gas technician for further advice.
You should also take the opportunity to test other gas appliances; check that all of the burners on the stove light properly, check the oven and grill (if fitted) light properly, check that the fridge (if fitted) works on gas - check it lights on gas and keeps the fridge cool (it may take a few minutes to get to temperature), check the gas fire works (if fitted) and finally check the gas water heating system (if fitted) to ensure that it works. Don't forget to check gas lights (if fitted) and replace broken mantles. Be sure to give the gas lights a good clean.When checking gas appliances, make sure that the caravan is well ventilated and if any appliance looks faulty, seek the help of a caravan dealer or gas technician.
6. 12v Electric System COST: varies for replacement parts DIFFICULTY: 2, Moderate
Some caravans have a 12v electric system run from a leisure battery. Caravans started to have electric lights as early on as the 1960's and 12v systems were becoming standard as of the mid 1970's. Some older caravans may have had a retro-fitted 12v system installed by a previous owner. All systems should be checked periodically. A 12v system can power a multitude of things including lights, water taps, 12v outlets (for shavers, vacuum cleaners etc) and radios. If you have any 12v appliances, you should check that they work properly. Also take the time to check the condition of the leisure battery. Test the battery for voltage and amperage using a multimeter and then remove it from the caravan and place it on a battery charger (you can pick one up from eBay for less than £10 and pay a bit more for a decent one) until it reads 13/14 volts. Your caravan charger (if you have one fitted) may already have charged the battery to a suitable level. Always switch off all 12v appliances inside the caravan before disconnecting the battery to prevent fusing. Check the condition of the battery terminals and sand them slightly if they are corroded. Also inspect cables for any signs of damage and if the protective coating is damaged, either replace the cable or apply electrical insulation tape for temporary repairs and repairs to small amounts of damaged. Electrical insulation tape should not be used as a long term solution.
7. 230v Electric System (If Fitted) COST: free DIFFICULTY: 2, Moderate
Should your caravan have a 230v system, this needs checking mainly to ensure that it works. Connect the mains lead to a power outlet and check that all appliances work as they should. Secondly, inspect the mains cable for damage. Here is a wiring diagram for the mains lead connector:
8. Water System COST: around £3 DIFFICULTY: 1, Easy
Fill a water container with water and check that the water system delivers water to the taps. Owners of caravans with an electric water system have an external pump (pictured) but caravans with foot pumps have a simple pipe. On a service, this pipe should ideally be replaced unless you have a 12v system water pump as per the image below - in which case the water filters should be changed. Consult your caravan dealer for more information.
12v operated systems may require new filters. Each system is different, but usually where the water inlet pipe is connected to the exterior of the caravan, there is a small unscrew-able lid which reveals a small removable filter unit. Alternatively, it may be under the bunk where the water system is located. These filter units can be bought from caravan dealers and the internet for around £4. A filter cleans out impurities in the water supply to provide fresh water to the taps.
9. Fitted Appliances COST: free DIFFICULTY: 1, Easy
Some caravans will have different appliances fitted. These should be tested out to ensure that they work and any maintenance such as lubrication should be carried out. A popular addition to vintage caravans is the fitting of a cassette toilet. This is a built in toilet with a tank which can be removed via the exterior of the caravan. This tank should be cleaned out using appropriate cleaning solutions and the cassette mechanism should be lubricated. You can also keep the seals in top condition using a spray by caravan toilet manufacturer Thetford. A 250ml spray can is around £7 from caravan dealers and will last years.
10. Finishing Off COST: free DIFFICULTY: 1, Easy
Finally, your caravan is ready to go. Treat it to a clean and a tidy up before embarking on your next journey. Remember to double check the tightness of the wheel nuts (see section 2) and check that the road lights work and you're ready for your next holiday!
I hope this article was helpful, please contact me with any comments and suggestions on how to improve it. Also as usual, feel free to ask any questions.