An auto electrician is a very skilled profession, more so today where most vehicles have miles of wiring and hundreds of sensors, so if you get a problem with the electrics, you’re looking at big money for diagnosis, unless of course you can do some of the work yourself … you’ll need one of the best automotive multimeters to help you through it though.
In past times, cars were pretty simple – you fed gas through the carb and it was ignited by a spark with a ‘points’ style ignition, there were bare minimum of wires, and what there was, were easily accessible and you could lay your hands on most of them without too much tear-down, modern cars aren’t that simple (which is both good and bad).
Why You Need A Digital Multimeter?
Of course, technology means that cars are bristling with sensors and wiring, it also means that these sensors are usually reliable, rarely breaking down or giving problems, but … and it’s a big one … when they do fail or intermittently work, it’s a huge job.
If you’re lucky, you can plug in a code reader to identify the fault – quite often it will tell you that there’s a fault, it may even give you a location or description of the faulty component, but it still doesn’t mean that component is truly at fault – it could be getting erroneous readings from something else.
It’s also worth knowing that even simple jobs under the hood can lead to electrical problems, especially if the car is a few years old. The wiring gets old and brittle, it’s almost molded and set in to place, so when you disturb it to fit an aftermarket cold air intake or whatever, you could set off a chain reaction of dry joints and bad connections.
But it isn’t just about fault finding, what if you want to fit an electrical accessory? Or work out max. loads on the electrical system? You definitely need a digital multimeter (DMM) for that, and if you choose the right one, it can also give you temperature readings, even an accurate tacho function so you can see what’s happening with the ignition. A quality automotive multimeter can give you so much more than a continuity or voltage check.
Best Automotive Digital Multimeter
I admit, my electrical skills aren’t as good as my mechanical skills – I can strip and rebuild a car, or $100,000 race engine with ease, but point me in the direction of capacitors, diodes, LEDs and wiring, and you’ll see a cool sheen of sweat on my brow.
That isn’t to say I can’t do electrics, just that I need to spend more thinking time on the problem. I mention this because some multimeters have literally hundreds of uses and functions, many aren’t relevant (to me), some of them you maybe use only once in your lifetime, but they’re all there, waiting to be used.
And that’s why choosing the right meter needs thought – sure, buying the all singing, all dancing most expensive meter almost guarantees you’ll have all the functionality, but can you use it? Will you use it?
I’ve chosen four different DMMs, ranging from the top of the range (with the aforementioned hundred uses) right down to simple (read: cheap) meter that should still cope with most of the average home mechanics needs.
I’ll start with the most expensive and work down to the least.
1. Fluke 87-V Digital Multimeter
The 87-V (which actually means 87 Five) is one of the electrical industry’s leading go-to multimeter’s for many of the professionals – whether that’s as a contractor, electronic techie, master technician … this is the leading DMM, and has been for years.
Some of the functions won’t really be applicable to the automotive guy (or gal) – like the ability to accurately read the frequency measurements on ASDs (Adjustable Speed Drives), so the Fluke designed ‘low pass’ filter will be irrelevant also, but the rest of it is all pretty handy – like the built in thermometer (with separate temperature probe) – I’ve found this function really handy (I actually own a Fluke meter).
It will read peak measurements and store the min and max readings, which is a handy feature for capturing intermittent problems, and is rated as CAT III 1,000V which means it can measure up to 1,000v in both AC & DC without a problem (not much call for that in the auto world though).
This digital multimeter is designed and built in the USA, and has a lifetime warranty (and if you do damage it, most parts are available separately). The large digit display is great if you’re needing to leave the meter on the fender while probing around the car, apart from that, there is an option for a magnetic hanger – great idea for any mechanic.
The unit comes with: TL75 test leads, AC175 alligator clips, holster and the 80BK temperature probe.
2. Amprobe AM-530 TRMS Electrical Contractor Multimeter
This again is designed for use within the electrical industry rather than purely automotive, and that’s noticeable with features like the non-contact voltage detection and True RMS, which helps to give accurate measurements (voltage & current) in noisy environments (we’re talking electrical noise).
That aside, it makes a useful addition to any mechanics tool chest, and it’s priced well enough to offer great features without breaking the bank. The AM-530 can do the usual DMM measurements, but also adds in a built in flashlight (you’ll be surprised at just how often you’ll use it), and of course the voltage detection – not that useful with a vehicle, but that just means it’s a great all-rounder for use in the home also.
It also offers a temperature measurement, and that alone makes it a great asset to a mechanic.
Included in the box: DMM, test leads, K-type thermocouple, battery (installed) Velcro strap, carry case & manual. In case you’re wondering, all testing has been carried out at the Fluke safety laboratory, so you know you’re getting quality and consistency.
3. INNOVA 3340 Automotive Digital Multimeter
The INNOVA has been designed to a professional automotive diagnostic tool, but still remaining well priced, especially when you consider the features it has.
Out of the four DMMs I’ve listed, this would be my choice, thanks to the added functionality like the inductive pickup clamp (for reading RPMs) and temperature probe – this is a great tool for fault finding and engine setups. I also like the fact that it’s auto ranging (useful for anyone that isn’t 100% sure of their electrical ability) and has an over load protection function built in – should keep those teeny tiny fuses safe.
Using this meter, you can test stuff like duty cycle, solenoids, breaker points, alternator diodes, switches and wiring faults – it really will do it all, without needing certification from Caltech. The case itself is pretty rugged, and has built in storage clips for the test leads, I guess my only gripe would be that it doesn’t come with any alligator style leads or clips, which I’ve found to be an essential part of automotive diagnostic testing.
4. INNOVA 3320 Auto-Ranging Digital Multimeter
If you’re in need of something simple, just for checking voltages or continuity and don’t want to spend more than a handful of dollars, this INNOVA meter should be your choice. The features it has make it a great tool for home or car, and it simplifies testing of certain things … a built in color coded LED scale will check batteries for example.
It’s also auto ranging and has a large digital display, which I think is a much underrated feature – you can place the meter pretty much anywhere in the car and still be able to read it – until you’ve had your head buried behind the dashboard, test leads in hand and still trying to see a meter, you won’t appreciate this added function.
The case itself is pretty solid and uses rubber corner guards, which should protect the meter from all but the most damaging falls or drops. Similar to the 3340, my only real gripe would be a lack of alligator leads or clips.
It’s cheap yet cheerful and does what you need.
The only thing that I’d really add to this, is that investing in a quality set of test leads is a worthwhile thing – some of the less expensive models have cheap leads, which can lead to poor readings (especially when measuring resistance), or total failure.
You can buy kits with quality test leads that use a longer length (always handy), a better coating for insulation (which helps with heat damage – great for under the hood) and a wide range of accessories – alligator clips, self-piercing, clamping, thinner contacts (particularly useful for getting inside plugs without separating them).
If you’re going to invest in a quality multimeter for your automotive needs, invest in a decent test lead kit also.