Saturday, June 10, 2023


RVelectricity™ – What is this mystery amperage draw?

Dear Readers,
I just had an RVelectricity group reader ask about what appeared to be a mysterious current draw of 20 to 40 amps on his GFCI branch circuit. It disappeared whenever he turned off the circuit breaker or hit the test button on the GFCI. And there was a 30-second delay after he turned the breaker back on or reset the circuit breaker before the extra current draw would come back on. Everything is unplugged from the outlets that are on the GFCI branch circuit, and all lights and appliances seem to be working properly.

He and his wife are full-timers boondocking with 1,000 watts of solar panels, and they’ve never seen this behavior before. So I suspected that something had changed, but the original installation must have been correct since it’s been working properly for several years.

However, this new and huge current draw would quickly deplete their batteries and they would be stuck in a cold and dark RV by the middle of the night. What to do, what to do…?

A riddle, wrapped in a mystery, inside an enigma…

Since there were dozens of questions from other group members that weren’t providing any clues, I asked the OP (Original Poster) to call me to confer. In less than an hour I had him on the phone. I’ve done remote electrical troubleshooting literally thousands of times over the last 50 years, so I had a pretty good idea of where to start.

So, here’s how I approach troubleshooting all electrical problems. You can use these same techniques to solve nearly any failure or problem, as long as you insert the correct skill sets. Yup, this basic troubleshooting process works for anything from RVs to steam locomotives to nuclear reactors.

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First Rule of Troubleshooting: Observe what is happening

The OP was mixing up 12-volt and 120-volt systems in his questions and responses. For example, while he originally said that the GFCI was drawing 20 to 40 amps of current, what was really happening was his battery monitor was showing an extra 20 to 40 amps of current discharge at 12 volts DC. This was feeding the inverter, which was turning this into 120 volts AC to power the GFCI circuit.

Second Rule of Troubleshooting: Start with simple possibilities

As I would tell my live-sound production students, I am a simple man who has to do very complex things. So, in this case I needed to break down the OP’s observations into their most basic forms. Now that we knew he was talking about 20 to 40 amps of 12 volts of DC current, we can convert that to around 2 to 4 amps of 120 volts of AC current flowing in the GFCI circuit. To calculate that, all you have to do is divide the current at 12 volts by a factor 10 to find the approximate current at 120 volts. That’s because 12 volts / 120 volts = 1/10. Simple arithmetic….

That’s a much more reasonable number since I couldn’t believe there was anything in an RV drawing an extra 20 to 40 amps of current at 120 volts. That would have been 2,400 to 4,800 watts of power, which would be heating up something quite rapidly and tripping circuit breakers. But 2 to 4 amps at 120 volts is only 240 to 480 watts, which is a much more reasonable number.

Third Rule of Troubleshooting: Think big picture…

That simply means you have to consider the entire problem, not just a single piece of data or only one observation. Don’t get stuck looking at a single tree when there’s an entire forest of possible things happening. Note that there was also the 30-second turn-on delay and the 20- to 40-amp variable draw at 12 volts to account for. Time to look at the forest and not just one tree…

So what in an RV draws 500 watts or so of 120-volt electricity and has a turn-on delay? A few readers posited that it could be the electric water heater element, but that’s typically 1,500 watts.

What about the furnace? That blower and controller runs from 12-volts DC, so it can’t have anything to do with the 120-volt GFCI drawing amperage from an unknown load.

However, there is one thing in an RV that draws around 500 watts and cycles on and off… the 3-way refrigerator running from electric power rather than propane.

Fourth Rule of Troubleshooting: Make a change and observe what happens

After confirming they had a 3-way refrigerator, I asked them to check if it was on propane or electric mode. While they normally had it on Propane (Gas) mode, somehow it had switched to electric/propane (Auto) mode. So the controller was turning off the propane burner and turning on the electric heating element whenever 120 volts was present. Of course, that’s not how this boondocking couple wanted the refrigerator to work since that would quickly drain the battery when boondocking.

For the test I had them switch the refrigerator to propane mode, and the extra 500 watts of power draw (40 amps at 12 volts from the battery) disappeared. This confirmed that the switch on the refrigerator had ben accidentally changed from Gas to Auto mode and that’s what created this entire failure that was draining the batteries. So the fix was simply to turn the refrigerator control to Gas (propane-only mode).

The debriefing… (It’s elementary, my dear Watson)

The variable 20 to 40 amps from the battery bank was due to the sun going down on the solar panels. Their battery monitor was only showing how much the battery was charging or discharging, and during the day the solar panels were providing around 20 amps of current at 12 volts. That was subtracting from the 40 amps the inverter was using to power the 500 watts of power the electric heating element in the refrigerator needed at 120 volts. And when the 120-volt AC power came back on after turning on the circuit breaker, the fridge control would wait 30 seconds to be sure the power was stable before switching to electric which power the electric heating element. Ta da!

[The following ad is inserted by Google.]

Teaching RV technicians how to troubleshoot…

From the time I got the OP on the phone and asked a few questions about what he was observing, to coming up with a simple hypothesis, and to confirming my guess with a test, took all of 10 minutes. But I’ve been doing this for 50 years professionally, and at least another 10 years while I was a youngster teaching myself electricity. That’s why I’m pretty quick at this.

However, this is exactly the type of troubleshooting process I’m trying to teach RV technicians for my Level-3 RVTI training. Without that logical thought process they could spend hours trying to figure out this type of failure unsuccessfully, all while billing you $150 per hour.

Advanced RVTI Training

With any luck, I’ll be offering extended RVelectricity training classes for certified technicians in 2022, and able to provide them with CEUs (Continuing Education Units). They need a certain number of CEU’s every year to maintain their Certified Technician status. And yes, there will be a test that will be graded.

It’s also possible that I could offer this same type of advanced classes to RV owners, as well (but not in the same classroom as the RV technicians).

It Ain’t Easy… (Thanks, Three Dog Night)

However, be aware that this level of advanced RV electricity training is pretty intense and time-consuming. Just my A-module for advanced electrical training will be three separate 3-hour sessions, for a total of 9 hours of instruction, not counting the tests. And these advanced classes will require a solid understanding of electricity just to get into this course at all.

BTW: Click on the album cover to hear this great classic song while you’re pondering how to get more training. 

Please let me know in the comments section if that level of training might be of interest to any of you. Depending on how it works out, this could turn into a monthly series of Zoom Classes, which would be recorded for your future reference. So let me know if you’re interested in this type of online class.

Upcoming Ask the Expert Webcast

In the meantime, I’m announcing a new Ask the Expert Interview on Thursday evening, December 9, 2021, beginning at 7:00 p.m. EST. This interview will feature Mike Zimmerman, one of the admins at my RVelectricity Facebook Group. Mike Z is not only an electricity expert and instructor on the National Electrical Code, he’s been an Electrical Engineer and Master Electrician for more than 40 years. Plus, Mike Z is also great at troubleshooting electrical problems.

This will be a Live YouTube Webcast that anyone can watch live or as a video later. And if you have a YouTube login account you’ll be able to text questions live to Mike Z and myself during the webcast. Sign up for an Ask the Expert reminder HERE.

Let’s play (and learn) safe out there….

Send your questions to me at my new RVelectricity forum here.

Mike Sokol is an electrical and professional sound expert with 50+ years in the industry. His excellent book RV Electrical Safety is available at For more info on Mike’s qualifications as an electrical expert, click here.

For information on how to support RVelectricity and No~Shock~Zone articles, seminars and videos, please click the I Like Mike Campaign.



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Micheal Whelan
1 year ago

Nice work on explaining trouble shooting in a methodical and logical manner. Now my problem is remembering it when the time comes instead of using my tried and true just jump to conclusions, get it wrong and then take it to the shop. I shall try to use your methods on the next project….. and then mess it up and take it to the shop. Thanks. There is hope for me yet.

Micheal Whelan
1 year ago

I have an issue as to the best way to use a “pulse charger” to charge the 4 six volt batteries in my coach. The pulse charger tends to deep charge the battery and help to “de-sulfate” the batteries I am told. My challenge is 2 of the batteries are under the step and two of the batteries are located on either side of the generator in the front of the coach. My logic says I should be able to put the charger on the two under the step (as they are close enough together for the charger clips to reach) and as all batteries are connected the charge would do all four batteries. Is my logic flawed?

Phil Justis
1 year ago

(Cont.) for the furnace. The factory had switched the wires. I had accidentally blown the other fuse when working on the furnace and after replacing the wire I had left the old wire touching the furnace housing, it was dead so why worry 😅. I didn’t think that the factory would have not labeled things correctly, my mistake. Sometimes a solution in the beginning is simpler than it first appears.

Phil Justis
1 year ago

I was asked to see why a neighbors furnace was not working and determined that the fan motor was bad and not coming up to speed and closing the sail switch. When the new motor arrived I removed the fuse marked for the furnace and proceeded to remove the furnace from the housing. Guess what the factory had installed a screw at the back of the furnace so I couldn’t remove the furnace until I got access to the back of the furnace. That done I changed out the motor and bench tested before reinstalling it. When all hooked up the furnace didn’t run and I determined that there wasn’t any 12v. at the furnace. Checked the fuse which was fine. Finally jumped a new wire from the fuse panel to the furnace and then the furnace worked. Come spring they called saying that the awning would not extend. Of course no fuse was marked for the awning but I found one fuse blown and replacing it immediately blew again. Finally noticed that the color strip on the wire that was blowing was the same as the wire

1 year ago

When working with two different voltages, it less confusing to think in terms of Watts rather than Amps.

Watts = Volts x Amps
40 Amps x 12 Volts is 480 Watts
480 Watts ÷ 120 volts is 4 Amps

1 year ago

I, too, learned Four Rules of Troubleshooting when I was repairing two-way radios as my first full-time job. I had a radio that a customer was certain had very limited range because all other vehicles were fine on range. I could find nothing wrong at all. The company chief engineer saw me struggling and taught me Four Rules of Troubleshooting that have served me well no matter the industry.

#1 – You can’t fix it if it’s not broke. 

No matter what someone has told you, if your testing finds no faults, look elsewhere. In other words, believe more in yourself than someone else.

#2 – If you mess with something long enough you will break it.

#3 – If something is broke, go find the person who messed with it last.

#4 – NEVER assume there is more than one cause for the problem UNLESS you have overwhelming evidence to the contrary. Once you start down the path of “If this was this way and that is this far out of tolerance…” you are hopelessly lost. Start over from a different angle.

1 year ago
Reply to  J J

That radio range problem? The chief engineer talked to the customer and asked if it was OK to send a tech out to test the base station. The customer was adamant there was nothing wrong with the base station because only one vehicle was affected and said he didn’t want to pay for an unneeded service call. The chief engineer made an offer the customer could not refuse.

The customer was coming up for his annual base station maintenance work (this was in the early 1970’s), The chief engineer told the customer that if our tech found nothing wrong then the customer would pay nothing and the customer would also get his annual maintenance check done for free.

The tech found their base station tower had taken a lightning strike. The strike damaged the antenna and transmission line but not the base station radio due to the lightning protection working as designed. This was the only vehicle that ventured far from their base station so the reduced range was not noticed by the other vehicles.

1 year ago

Yes, I would love the rv owner classes.

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