Aren’t we lucky? We have opposable thumbs and we make tools! In this section of the RV PHD we’ll talk about tools that are great for RVers and techs to have in their toolbox.
Arguably the most important tool in the tech’s toolbox is an AC/DC amp clamp digital multimeter (DMM). And, with the cost having dropped dramatically over the years, there’s no reason not to have one. It is essential to use a DMM not only for accuracy, but to improve customer service, end comebacks for repeating problems, and, in the end, save time making repairs.
The RV PHD Newsletter is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber.
Why an AC/DC clamp multimeter?
RVs are full of electrical and electronic systems, both 12-volt DC and 120-volt AC. With the complexity of these systems, the DMM is essential for troubleshooting faults and coming to a diagnosis.
Even if you’re not inclined to service or repair your own RV, the DMM can help an online or on-phone technical agent help to find a cure for whatever ills your rig.
For techs, I quote former Ford CEO Alan Mullally: “The data will set you free.” Troubleshooting with the right information is the difference between a parts changer and a true technician. The DMM will provide you with the data needed to make a correct diagnosis you can hang your hat on.
I recommend an AC/DC clamp DMM because today’s RVs often have advanced DC energy systems, including solar, lithium battery systems, inverters, and more electronics than a Radio Shack. In fact, the DC electrical system is the main electrical system for all RVs except park models. Sometimes, it is necessary to see how much amperage is being consumed, and a DC clamp makes that super easy with no wiring work required. Of course, the same goes for AC, and there are many AC-only DMM clamp meters out there, but having the DC is important for RV work.
What features should I look for in a DMM?
Besides the AC/DC amp clamp, the following are important to have or consider:
- Automatic ranging- this simplifies the operation of the meter. Manual meters require selecting the appropriate range for the system you’re testing. An auto-ranging DMM will select the best one within the meter’s capabilities. You can, of course, still manually select a range if you wish.
- Most DMMs in this class will have AC and DC voltage, amperage, resistance, capacitance, continuity, and diode testing.
- Temperature probe- While infrared guns are nice, they only read surface temperature. A probe can read both air and surface temperature. This is important for diagnosing air conditioning and refrigeration issues. Tech service will often ask for a delta-T temperature reading on an air conditioner to see how it operates, which precisely measures the discharge and return air temperature.
- Non-contact voltage tester- The NCVT is convenient for checking for AC voltage without touching the potentially energized equipment. While a handheld NCVT may be more sensitive, it’s always good to have the capability in the meter.
- Backlit display- Necessary when testing in a dark environment, like inside a cabinet or a motorhome basement.
- Stand or probe holder- It is essential that the meter be placed in a safe location before testing. A stand can be helpful for this. Some units may have a probe holder allowing you to use two hands safely while testing.
- AC Frequency- Not all meters have this capability, which is needed only when testing AC gensets. An upgraded or “pro” model will often add this feature.
How much should I spend on a meter?
Fortunately, you don’t have to spend much money to get one that will handle RV service work. Of course, Fluke and Extech meters are excellent, and if you want something of that caliber, great. However, we seldom deal with anything over 400 amps or 120 volts, so a CAT-III meter is sufficient. It will still do fine for split or three-phase power up to 600 volts AC or DC. Southwire sells the 21550T AC/DC amp clamp DMM, perfect for RV use (without AC frequency), on Amazon for $81. If you’re an RVTI-certified RV technician, you can get this meter at cost on your RVTI dashboard store.
This is not to say that meters by Fluke, Extech, and others aren’t good, they are. I have an Extech that I have had for decades, and it’s a great unit. The Southwire meters work fine for RV work at a lower price point.
DMMs are no good if you don’t know how to use them
Practice makes perfect. When you get your meter, practice with it. Keep it handy. Try using each function of the meter and see what results you get. Be sure to read the manual that comes with it, and look online for videos on using your DMM. My friend Mike Sokol has some great videos on his YouTube channel. Your RV is a great place to test both AC and DC systems, testing for continuity, resistance, and temperatures.
We will use the multimeter in future articles and projects, so watch out for these.
The RV PHD Newsletter is a reader-supported publication. To receive new posts and support my work, consider becoming a free or paid subscriber.
