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Checking the health of your motorhome


Words and photos: Peter Rosenthal


Former MMM Tech Editor, George Collings, coined the phrase ‘sleepy van syndrome’ to describe the issues that can occur on almost any motorhome during long lay-ups.

Motorhomes and campervans that are not used all year, or have been parked up during lockdown during 2020 and 2021, are especially susceptible to this.

So, before you twist the key and point your motorhome towards a campsite, it’s wise to carry out a few simple checks.

It’s tempting to jump in your motorhome and fire it up – but hang on. Think about the battery voltage. If we had a pound for every tale of woe that involved low battery voltage, we’d all have retired to a large mansion.

Almost every aspect of your base vehicle and habitation equipment relies on correct battery voltage to function correctly.

In the case of your habitation batteries, do not pass go – simply plug the vehicle into the mains hook-up and leave it overnight before you test any internal system of the motorhome.

Not all motorhomes recharge the vehicle battery when they’re switched off and not all habitation charging systems also recharge the vehicle battery, so you need to check this.

If your vehicle doesn’t have a starter battery charging circuit, then you can easily add one – we featured fitting a Van Bitz Battery Master in the May 2021 issue, but you can also get similar systems from Votronic (via RoadPro) and Sterling.

While you could use a separate charger (like a CTEK) to recharge your vehicle battery, it’s best to have one of these automatic systems fitted as they not only work when you’re on a mains hook-up, but also divert battery to battery and solar panel charge into your vehicle battery. Fit and forget!

So why does the vehicle battery discharge? During lay-up, you’ve probably gone into and out of your vehicle several times.

Each time you press the key fob, the lights flash, the central locking activates, the ECU wakes up and goes into a ‘getting ready to start’ state. Then when you open a door, the cab lights illuminate.

All these functions take a small bite out of the battery voltage. With the vehicle laid up and no alternator current to recharge the vehicle battery, the voltage will fall over time.

Even if you don’t go in the vehicle at all, there’s an amount of natural discharge that batteries show. If the vehicle also has an alarm or tracker system, there’s an additional drain on the battery.

When the battery voltage is low, you’re far more likely to blow fuses or cause damage to the electrics. This sounds counterintuitive, but is due to the fixed power requirements of certain parts.

If your starter motor needs 1,200W to crank it and your battery is fully charged at 13V, it will draw 92 amps. If the battery voltage drops to 11V it will draw 109 amps. Components have fixed power requirements so if the voltage drops, the current increases to compensate.

As you unlock the vehicle, open the bonnet and check the battery voltage with a multimeter – especially if the lights don’t flash or the central locking doesn’t operate.

A fully charged lead acid battery will typically be around 12.6 to 12.8V when fully charged; at around 12.3V it’s around half-flat and a reading of 12V or less means it’s flat and needs to be recharged.

With the base vehicle battery fully charged, it’s safe to turn the key and check the engine starts and runs fine.

It might be a little grumpy after lockdown and might be reluctant to start – different grades of diesel are seasonally supplied and if it’s not been used for a while it could still be running on winter diesel (which has extra additives to protect it in cold temperatures).

Typically, winter diesel is supplied from mid-November to mid-March, before firms swap to the slightly more viscous summer diesel.

Winter diesel is fine to run in summer, but, before winter lay-up, you want to refill the tank at the end of November so you don’t have issues with summer fuel causing starting issues in the freezing temperatures.

Time for a motorhome service?

If you haven’t started the engine regularly during lay-up and let it warm up to operating temperature, then all the engine’s drive belts will have been static in one position.

Like tyres, belts don’t like sitting in one position for long periods. So, if your cambelt is due replacement this year, it’s wise to do it sooner rather than later. Cambelt failure is unusual these days – the belts are incredibly durable and reinforced with fibres – but not unheard of.

Cambelts should be replaced at the correct time or mileage intervals – low-mileage motorhomes must change the belts at the correct time period.

It doesn’t hurt to change them a year early, either, and always use a premium brand such as OE, Gates or Continental.

Always get the other engine drivebelts checked at the same time – they’re not expensive to replace while the cambelt is being done.

No matter what the service schedule, it’s always wise to have the vehicle serviced annually, even if you’ve only done a tiny mileage, or if you have used your motorhome over lockdown and done far more short journeys than usual while doing essential trips or supermarket runs.

Diesel engines tend to produce more soot than petrol engines and low-mileage vehicles that only even do short journeys tend to clog their emissions systems. They also tend to turn their oil black with deposits far more quickly than petrol engines – so an annual oil and filter change is wise.

While the garage is servicing the motorhome it also gives it a chance to do a safety check and advise you about replacing brake parts, suspension struts and tyres – great for peace of mind for the holiday season.

Short trips over winter, where the engine rarely gets that warm, are not good for engines and diesel engines in particular will suffer. They’re designed to do high mileages and rely on high motorway temperatures to burn off carbon deposits and keep the emission control systems operating perfectly.

To avoid issues, at least once a month make sure you run the engine at higher revs than normal for a sustained period. This will get the engine hot, burn off carbon deposits and help remove gunk from the vehicle’s emissions systems.

Running a diesel engine at low revs in high gears will do it no favours – if you’ve never got the engine hot enough to trigger the vehicle’s radiator fan, it’s not been hot enough to burn off any deposits and may have issues with emissions. So, rev it to avoid issues.

Habitation servicing on motorhomes and campervans

Although most people religiously follow the base vehicle servicing schedules, the same can’t be said for the habitation equipment. We’d always recommend getting your habitation kit checked at a main dealer at the start of the season.

This typically involves a thorough damp check – vital for all coachbuilt and A-class models as early warning of any water ingress issues – as well as a comprehensive check of all the vehicle habitation systems.

As well as checking the gas pressure, making sure the regulators operate correctly and ensuring that the burners on the hob, heater and boiler are working correctly, a habitation check will also test all the electrical systems for safety and that the plumbing systems are also operating correctly.

The common items that need regular attention are cleaning the gas burners in the hob and fridge – much like the emissions system of the base vehicle, these get clogged up with contaminants and need to be in pristine condition to ensure that the gas burns cleanly and efficiently.

A sure sign that your gas system needs looking at is if the flame on the gas hob is yellow or sooty – anything other than an even blue flame, means the burner needs attention. It’s very important to have your gas system serviced annually to avoid excess carbon monoxide being produced.

Cleaning a motorhome

Let’s be honest, cleaning a motorhome can be quite a chore so we’d recommend using a soft-bristled brush and tub of warm water with car shampoo in it to get the worst of the dirt off the vehicle. Do not use household detergent as it’s too aggressive for vehicle bodywork and can cause issues.

You can also use your local car valeting firm to wash the vehicle, but make sure they only use mild detergents and do not use any acid-based cleaners on the wheels (brick cleaning acid is commonly used – if the valet costs under a tenner, corners will be cut).

Equally, great care needs to be taken around the seals and vents if they use a pressure washer. Only use a pressure washer at distance, never close up – at best it will remove stonechips touch-ups, at worst they can strip lacquer and lift off graphics.

The best way to clean your vehicle is to simply get your motorhome dealer to do it at the same time as the service – get it to clean the roof, too, as this is commonly missed.

Motorhome and campervan tyres

If your vehicle has sat in one place for an extended period of time, then those four (or six in the case of double or tag axles) round black donuts of rubber might need a little attention before you drive off. All tyres naturally lose pressure over time, so the first thing to check is the pressure.

MMM has long championed the best method of working out the pressures: visit a weighbridge in a touring-ready state and weigh each axle; then contact your tyre maker and get its recommended pressures for the front and rear axles.

Do not drive to a local garage to inflate your tyres as you risk sidewall damage if the pressures are low. Inflate the tyres with a compressor before you turn a wheel.

The next issue will probably affect quite a lot of people this year and was something that my own campervan suffered from: flat-spotted tyres. Motorhomes sat for extended periods without being moved can put a sizeable load on a tyre in one place.

This can distort the tyre and, when it’s pressed into service, can cause vibrations or, in extreme cases, even cause a blowout.

In my case, the campervan had a vibration that started at 40mph and got steadily worse so that at 70mph it rattled and shook unpleasantly.

Dipping the clutch made no difference so that ruled out engine and gearbox, leaving tyres, wheel-bearing, driveshafts and dampers.

Tyres are the easiest to check and, after jacking the vehicle up and spinning the rear tyres, I found that both had gone egg-shaped over lockdown.

By the time the new tyres arrived, the tyre carcass had already started to show through the pointiest part of the egg-shape – this was over just three days – so it’s not something that you can ignore.

The tyre centre reckoned that one of the tyres could have been damaged on a pothole as well (they were four years old and had covered 42,000 miles), but that didn’t explain the damage on the other one – clearly lockdown took its toll.

Some flat spots are temporary and may resolve themselves as you drive. The usual trick is to drive a short distance until the tyres are warm to the touch and then jack the vehicle up in the air with all wheels off the ground – it’s not easy to do this yourself, so ask your local dealer to do it – in the hope that the tyres reshape themselves.

Sometimes this works, sometimes it doesn’t. If a vibration persists, you will need new tyres.

So if, after inflating the tyres to the correct pressure, you feel a persistent vibration that doesn’t disappear when you dip the clutch or vary with engine revs, get your tyres checked immediately. Any tyre centre will only be too happy to advise you.

We’d suggest you do this well in advance of any planned trips as some tyres can take longer to get hold of than others (especially certain sizes of motorhome-specific ‘CP’ marked tyres). Brexit-related port delays and factory shutdowns due to the pandemic have all increased lead times of certain brands and sizes.

Habitation equipment

With your leisure batteries fully charged (plug into mains hook-up!), it’s wise to give all your habitation electrics a going over.

Flick every switch and make sure every electrical item works. If anything doesn’t work, then firstly check that the vehicle has power (is the vehicle’s charging system switched on?).

You can plug the vehicle into the mains to check your appliances, but make sure your consumer unit indicates that it has power and that it hasn’t had any RCDs trip out.

If some items are working, but not others, then you’ll need to check the fuse box (it’s common to pop fuses if you’ve not plugged the vehicle into the mains) and see if any fuse has blown. Most are clearly labelled with what fuse does what.

Remove the fuse and either see if it has blown visually or check it with a multimeter set to read continuity (better). Multimeters cost as little as a tenner and are easy to use so it’s worth buying one as a simple fault-finder.

If a fuse has blown, replace it with a good-quality fuse from a reputable source (not a cheap pound shop one – these give issues) and make sure the replacement has the correct current amp rating.

In the case of heating systems, make sure it is filled with fuel – usually diesel or gas – before you test it. Their inbuilt safety systems mean that they won’t work if their fuel is low.

Sometimes stale diesel can cause issues for diesel heaters, so it’s a good idea to get into the habit of running these up to temperature every few weeks over winter.

Most motorhome fridges have a vent setting for lay-up (always switch the fridge off and use this, or prop open the door, to avoid mould forming inside) so make sure you’ve switched the latch to the locking position.

It’s wise to switch the fridge on the day before you travel – while on a hook-up – to ensure it gets down to temperature before you travel.

Three-way fridges are at their least powerful when running on 12V power, so don’t rely on just 12V power en route to your campsite.

Other batteries for motorhomes

One set of batteries you might forget about are the AA or 9V batteries fitted in your smoke alarm and CO detector. Press and hold the test button and, if you hear nothing, replace the batteries, or check the use-by date of the smoke detector – they do not last forever, so replace the unit if in doubt.

Avoiding water issues in motorhomes

A common lay-up issue is that water starts pouring out from under the vehicle when you first try and top up the water tank. Nine times out of 10 this isn’t anything to do with frost damage, but down to the automatic drain valve fitted to your water boiler.

These safety devices trigger automatically in cold weather to avoid the water freezing in the tanks and causing issues. Check the location of the valve in your manual – they’re normally next to the water boiler – and reset the switch.

Fill the water tank up a little and check that all your taps and showerhead are working fine. If there are any issues, open one tap at time – starting with the one furthest from the water tank – and leave them open until the water stops spitting out of the tap. Smooth-flowing water means you’ve eliminated air bubbles in the pipes and have purged the system.

If you can’t hear the water pump running when you first open a tap, check that the fuse to the water pump hasn’t blown.

If the water pump fuse is OK, then try another tap. If just one tap doesn’t activate the pump, it probably due to an issue with the microswitch on that tap. Check the wiring and if that’s intact, you might need to replace the tap – microswitches do fail from time to time.

If you can see water or damp patches inside the motorhome after you’ve filled the water tank, you need to check for leaks due to frost damage.

Pipes can split or come off at joints and things like water filters can drip water and split. Usually, these things are pretty simple to fix, but it all depends where the leak has occurred.

The presence of any mould or markings on furniture can indicate a water leak, so always investigate it if you see any discolouration or if your nose detects a ‘wet dog’ smell.


Unused touring kit

It’s a good idea to check over all your touring kit on an annual basis. Even those things buried at the very back of your garage.

As well as giving you unhindered access to the vehicle’s structure to spot any leaks or issues, it’s a good exercise to ensure that you don’t pointlessly lug things around and waste your precious payload.

Ask yourself if you really need to cart an item around in your motorhome if it hasn’t been used for over a year.

You’ll probably find items that you had completely forgotten about – leave them at home and save weight and fuel.


Checking your motorhome – in summary

Getting into the routine of carrying out a few basic checks and preparing the vehicle before you set off is a simple way to ensure no issues on your precious holiday time.

Combined with an annual habitation and base vehicle service, it will keep your motorhome in tip-top condition for many years to come.


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07/05/2021 Share this story   Share on Facebook icon Share on Twitter icon Share on Pinterest icon Share on Google Plus icon Share on Linked In icon Share via Email icon

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