James StanburySee other accessory reviews written by James Stanbury
A multimeter will help you solve electrical gremlins on your motorhome holidays or at home – read our group test to find out which is the best
How many tools do you take with you on your motorhome holidays?
Some people are cavalier and take nothing. Others are ultra-cautious and stash half of their garage away in their ’van.
In reality, being prudent is somewhere in between. From an engineering point of view, anything other than a wheel-changing kit is probably too much – modern vehicles don’t drift out of tune, or need adjusting.
So if they come to a grinding halt, it’s because something has failed, and all the tools in the world won’t help you if you don’t have a replacement component to hand. In short, major problems are always going to be a job for your favourite rescue service or a garage.
What’s bugging you?
Dealing with gremlins is a different matter. Hinges and locks can work loose, bulbs fail and electrical faults are not uncommon.
A selection of screwdrivers, spanners and sockets will deal with the former, but a multimeter is essential for tracking down electrical bugs and fixing them.
A digital multimeter is a test tool that measures voltage (volts), current (amps) and resistance (ohms), and is typically used by electricians.
The good news is that these meters are now cheaper, in real terms, than they have ever been – less than £20 can get you a piece of kit that will deal with almost anything your motorhome’s electrics can throw at it.
What we’re looking for
To appraise our selection of multimeters, we kicked off with the basics.
We expected all models to handle voltage, current and resistance measurement, but were surprised to find that current measurement – in amps – seems to be problematic.
Some models don’t do it, and others stipulate such a low maximum current to be measured that they are useless for anything other than delicate electronics.
Another feature we considered essential is continuity testing. Or, to put it simply, the ability to test whether a component, or wire, allows electricity to flow through it or not.
You connect one meter lead to one end of the item being tested – say, for example, a fuse – and the other lead to the other end.
If the meter is able to send current down one lead, through the component, and back to the meter through the other lead, it will beep and update the screen accordingly.
Again, we were surprised to find that not all meters have this dedicated function – even if it is possible, with a bit of know-how, to use other functions to carry out the same test.
Temperature probes and measurement used to be the preserve of premium multimeters, but now many budget units cater for it.
Normally, the probe can be exposed to several hundred degrees Celsius of heat, which means that the meter can be used for all manner of practical tests, from checking air-conditioning or fridge/freezer performance to simply measuring ambient temperature.
On older motorhomes, with ovens lacking thermostats, it’s not unknown for multimeter probes to be fed past door seals to accurately monitor oven temperature, too.
Is it worth the expense?
Obviously there are many other functions, beyond the scope of our reviews, that are simply not relevant for basic electrical work.
However, in the course of our tests, if a meter is expensive, we made sure it has a suitably comprehensive specification to justify its high price-tag.
There’s also the question of how to use a multimeter – how easy is it? And not just if you’re a novice.
Decent-length leads are always a bonus and we prefer a unit to come with test probes and crocodile clips, so you don’t need three hands at once to securely hold the meter and each lead in place.
The display is another issue. The clearer the digits are, the better. And some form of backlighting is essential for not only night-time emergency usage, but also when working in darker areas.
Sometimes, the meter has to be positioned in a place where you can’t see the screen at all. In these instances, a display hold, or freeze, button is invaluable.
Ideally, you’ll press it prior to disconnecting the meter and it will freeze the result on screen until you choose to clear it.
One final display feature we like to see is a bar chart. When testing components such as dimmer switches, the voltages don’t matter as much as making sure that the voltage increases and decreases smoothly as you rotate the dimmer switch.
With a traditional pointer-and-scale display, this is easy to see. Not so with rapidly changing numbers on a digital screen, unless said screen also has a digital bar display. So any unit with that feature gets extra points from us.
Silverline 513121 – four stars
- Price: £14.04
- Web: silverlinetools.com
Only a few years ago, a meter of this specification would have cost two or three times its current price.
That’s not to say it’s especially sophisticated; it isn’t. In fact, we can sum it up as basically doing all that Draper’s dearer 60792 (down the page) can, but with the addition of temperature measurement and a probe.
Like the Draper, this Silverline product’s clear display, display freeze/hold function, and nice long leads make this a doddle to use.
There’s even a protective rubber shroud to prevent damage should the meter be dropped. In fact, the only real advantage the 60792 has over this unit is that its display is backlit.
Whether that justifies the six quid higher price, especially with the lack of temperature measurement, is debatable.
Gunson 77038 – three stars
- Price: £78.22
- Web: gunson.co.uk
This is a test probe with a host of multimeter functions built-in.
In use, having the unit permanently connected to earth and simply measuring voltage by placing the spiked probe against the cable or component being tested is so much quicker and more convenient than having to continually disconnect and re-connect two cables.
In fact, it quickly becomes apparent why many auto electricians prefer probes to meters. But there are drawbacks, too, such as the screen being in an unreadable position.
And while the unit has a couple of very sophisticated functions, essential basics such as current and temperature measurement are absent.
Laser 5990 – four stars
Practical Motorhome Editor's Choice
- Price: £92.57
- Web: lasertools.co.uk
A glance at the specification reveals this meter to be pretty advanced, as well as expensive.
Its ability to measure frequency, electronic duty cycles and even ignition dwell means it can test modern engine management sensors as well as being used to accurately set up ignition systems on classic petrol engines.
All very impressive, you’re probably thinking, for testing the condition of your motorhome’s engine – and you’d be right. But sophistication is only half the story with this multimeter.
Thanks to large, bold, 18mm-high digits, this is one of the easiest-to-read screens here. And the digits are backed up by a useful bar-chart display, and it has plus display hold and temperature measurement.
Only its high price stops it from getting five stars.
Draper 60792 – three stars
- Price: £35.55
- Web: amazon.co.uk
A sound all-rounder, whose middle-of-the-road score reflects that other models do just as much but for a fair bit less money.
The 60792 caters for electrical basics well – such as current, voltage and resistance measuring, plus continuity testing – with one small proviso: take care when measuring current. Exceed the 10 amps maximum and you’ll damage the meter because the current-measuring function isn’t fuse-protected.
That aside, this is a pleasing piece of kit to use. The digital display is easy to see and can even be backlit when working in dark cupboards.
A hold button also allows you to freeze the screen, should the meter be in a hard-to-view position during a test. Decent-length leads are another bonus.
Sealey MM20HV – three stars
- Price: £24.54
- Web: sealey.co.uk
Another very credible sub-£25 multimeter. Perhaps the unit’s most striking feature is its high-visibility protective shroud.
Ironically, though, the screen is considerably less visually appealing. Not only are the digits just 10mm high – unlike the 15mm digits on most of the budget entries – they also don’t contrast so well with the background.
A problem not made any better by the lack of any form of backlighting. In use, all of the electrical basics are catered for well, and Sealey throws in a probe to allow temperature measurement.
Draper 37317 – two stars
- Price: £19.44
- Web: drapertools.com
And now for something completely different... this is the only one with a pointer-and-scale display instead of a digital screen. But the novelty of said display quickly wears off.
After the convenience of simply viewing numbers on a digital screen, trying to figure out which scale is the right one – and where the pointer lies – is a faff. Especially when the numerals on the scales are tiny, too.
It won’t come as a surprise that the display isn’t backlit, and that there isn’t a hold function built-in.
But more of an issue is the restrictive current measurement the unit allows – a paltry 250 milliamps is it. Not good when almost all other meters manage up to 10 amps.
Sealey TM101 – two stars
- Price: £39.45
- Web: amazon.co.uk
Sealey’s second offering is a peculiar mix. The mid-range price had us expecting some of the advanced features found on Laser’s 5990. But apparently not.
One unique function, though, is an end-mounted voltage sensor. Simply place the sensor next to a cable you suspect may be live, and the meter will tell you whether it is or not.
Another plus point is a large screen: at an inch high, this unit’s digits even outclass the excellent Laser’s.
But, those two points aside, we essentially have a basic multimeter for semi-professional money. The lack of temperature measurement, screen backlighting and display hold all ate into the score as well.