As an RV electrical expert, I’ve learned that a basic digital multimeter can save you a world of trouble on the road. In this article, I’ll show you how to quickly test pedestal voltage, check your battery’s state of charge, and find a blown fuse—simple steps that can prevent major problems. These are easy checks every RVer should know, and I’ll walk you through them.
Testing AC pedestal voltage
Use a meter to test a pedestal for proper voltage and polarity before plugging your RV into it. It’s actually pretty easy. Here’s the diagram I made years ago that shows all the voltage readings for a correctly wired pedestal.
If the voltage reads much below 105 volts or above 128 volts, then there’s a problem with the campground electrical system that could damage your RV or even create a hot-skin voltage condition. Below is a video I made that shows how to test a pedestal for proper voltage.
Testing DC battery voltage
Few things are more disheartening than waking up in the middle of the night with a dead house battery. Any digital multimeter will be more accurate than the simple 4-bar battery gauge in many RVs. But you will need to know what kind of batteries you have (such as flooded lead acid, AGM, or lithium).
Then find a SoC (State of Charge) chart like this one that shows battery SoC at different voltages.
This is also a great way to determine if your converter/charger is working. When you’re plugged into shore power, you should measure between 13.5 and 14.5 volts on your battery terminals, depending on battery chemistry. If you read in the 12-volt range, then your converter isn’t charging, and you’ll soon have dead batteries.
Finding a dead fuse
All these meters have a continuity setting, which will beep when there’s a low-resistance connection across the probes. By pulling the fuse and placing the probes across the fuse contacts, if the meter “beeps,” then the fuse is okay.
If the meter doesn’t “beep,” then the fuse is blown. It’s also possible to check the fuse in-circuit. With the power and the load on, set the meter to 20 volts DC. If you measure 12 volts across the fuse, then it’s opened up and not passing current. But if it reads close to 0 volts (maybe 0.5 volts DC), then the fuse is good and is supplying current to the load.
Lots more things to test
The list of things you can test with a basic digital multimeter is nearly endless. You can measure hot-skin voltage, find a dead GFCI, troubleshoot an open contact in a generator transfer switch, check AA and 9-volt batteries for juice, and a whole lot more. I won’t go anywhere without my trusty multimeter.
But you need to learn how your meter works when you’re not under pressure. So get a multimeter and read about how to use it HERE. And then when something in your RV stops working, you can pull out your meter and start troubleshooting.
HERE is the article I wrote previously about various meter kits you can purchase at big box stores and Amazon. You can get a nice kit for about $45, or just a digital multimeter for around $25. Here’s the kit I recommend.
This question to Mike and his response were originally posted on RVtravel.com in 2022.
Mike Sokol is an electrical and professional sound expert with 50+ years in the industry.
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