How to Troubleshoot & Fix RV Water Heater Electrical Problem

This is gonna be one of those posts with way too many photos, but not because it’s one of my random collections of Fun Friday Photos. With this one I hope to assist anyone who may need help to troubleshoot and fix RV water heater issues. Specifically, I’ll show how to repair an RV water heater that no longer heats water.

This isn’t the first time I’ve written about servicing an RV water heater. Knowing how to replace the water heater anode should be on every RVers annual maintenance list. I’ve even previously provided steps to replace the water heater element when your RV water heater no longer delivers hot water. But this job seems to get more complicated each time. This time I include how to replace the water heater thermostat. But you’ll see its really not all that complicated.

What To Do When Your RV Water Heater Won’t Get Hot

When our hot water wasn’t very hot one day, I knew I had a new project on my hands. The first thing was to determine why the water wasn’t heating up. STEP 1: I switched he water heater from AC electric service, to gas on the DC circuit. Good news! By burning through propane, we would at least have hot water while I got the parts needed to repair the electric RV water heater.

Rene was leaving me for her Tucson show, so I wanted to ensure I had all the parts necessary to do the job. I decided to get a replacement RV water heater thermostat switch, in addition to a new electric heater element. Good thing I did. But how do you know if the thermostat is bad? What if the power switch was the problem?

NOTE: Click photos to enlarge and view in Gallery mode.

Steps to Service and Repair RV Water Heater

Follow these steps to troubleshoot electric RV water heater problems, and replace electrical parts to repair the water heater when it is no longer doing its job. While your at it, perform the regular water heater servicing that is likely long overdue in most RVs.

Drain and rinse water heater tank
Replace RV water heater anode
Replace electric water heater element
Diagnose faulty water heater thermostat
Replace thermostat switch
Investigate and repair faulty power switch

1. Maintain your RV water heater with regular servicing.

Turn off power to your water heater. Make sure both the gas and electric switches are in the OFF position, and wait a while for water to cool down.

Find the water heater bypass valve, usually located inside the RV behind the heater. Turn the valve to prevent water from entering the tank. This will also allow you to use (cold) water while you perform your service and repairs.

Remove the vented panel to access the water from outside your RV. Flip the lever on the pressure release valve to – yup, you got it – release pressure from inside the tank. WARNING: This water may be hot!

Remove the water heater anode rod to drain water from the tank. You will need a 1 1/16″ socket with wrench extension. Read my previous post about how to replace the RV water heater anode and why, for details about what the anode does – and why you need to replace it periodically.

Allow all water to drain from tank. See prior note about potentially hot water. Do this step before removing any of the electrical component covers I discuss next.

Attach a water heater tank rinsing wand to the end of your hose. Insert the wand and turn on the water to thoroughly rinse the tank and remove sediment that collects at the bottom of RV water heater. I find it works best to rotate the wand 360 degrees while holding it all the way in, then pushing it in and it out to allow built up water pressure to carry debris away. Allow all water to drain out and clean anode opening threads of any debris.

2. Replace Electric Water Heater Element

NOTE: To access the electric water heater element, you will need to remove the gas supply manifold and burner assembly. This component contains very small parts which are easily lost or reinserted incorrectly when disassembled. To avoid this, remove the entire assembly intact. For more information and detailed steps, see my prior post about how to replace the electric water heater element.

Read on for electrical component diagnosis steps and download a detailed service manual and troubleshooting guide for the Suburban RV water heater.

Ensure that gas and electric power switches are turned off. Loosen retainer nut at end of gas supply manifold tubing.

Remove nut holding burner assembly in place.

Loosely replace nut on burner retainer bolt so you don’t lose it, and set assembly aside.

Remove cover to access electric water heater element, using a flathead screwdriver.

Use a Phillips screwdriver to disconnect wiring from water heater element.

To remove the element, you will need a Hot Water Heater Element Wrench. Place the socket over the element head. Insert a screwdriver into the holes at the end of the wrench. Turn counter clockwise to remove the element. (Clockwise to tighten the new element.)

Use silicon plumber’s tape to ensure a tight seal on threads for both the water heater element and anode.

Replace the anode rod and element. Re-connect the AC power wires to the water heater element. It does not matter which color wire connects to which screw. Do not over-tighten, one quarter turn past hand tight should suffice. Replace cover to seal electric heater element.

DOWNLOAD: Suburban RV Water Heater Troubleshooting Guide and Repair Manual

This Suburban water heater repair manual is very helpful for troubleshooting the electrical power circuit to diagnose potential problems. Follow the steps it contains for tracing power through the system to locate any short or break that may be causing the element to not heat up.

NOTE: Do not “dry fire” the electric water heater element. Ensure that the tank is filled with water before turning the power on. I didn’t bother doing this because I was replacing the element anyway, and I only momentarily turned on the power to test the components.

3. Troubleshoot Electric Water Heater and Replace Thermostat

NOT PICTURED: Test for proper voltage on each side of the water heater element by touching one probe of your multimeter to each screw, while touching the other to common ground.

Remove the square black cover to expose the RV water heater thermostat switches. These components prevent overheating by breaking the electrical circuit. Damage may not necessarily be visible. The two thermostats are also nearly identical. unless you look very closely at the numbers stamped on them.

For my reference, I marked which one was the 120 AC thermostat (Left), and which one was the 12v DC switch (Right). For your convenience I’ve confirmed the following part numbers:

Be aware that the position of your thermostat switches may differ. Set your meter to DC for testing voltage to both sides of the 12v DC thermostat.

Set your meter to the AC setting for testing voltage to both sides of the 120v AC thermostat. Please note that a good voltage reading may not necessarily mean the switch is still good. I read proper voltage for both of our switches. Since I had the part, I replaced it anyway. Especially after what happened next.

WARNING: Do not short thermostat when testing switch voltage!

Taking a second reading, just to make sure both ends of the thermostat were showing adequate voltage, I accidentally touched the probe of my multimeter to the base of the switch, while still contacting the overlimit sensor tab – or whatever you call that business end of the thermostat. 😮 Don’t do this.

So…this is what a faulty thermostat may look like. 😕

And the corresponding voltage drop would be obvious.

REMINDER: Ensure power switch is turned off.

Remove wiring clips from switch connector tabs. Use 3/8″ socket to remove retainer nut from thermostat base connector post.

Place new 120v thermostat switch assembly onto post and reattach wiring connectors.

If you do not have a small enough socket wrench, grip the small retainer nut with your Trusty Leatherman. WARNING: That small nut could easily slip out of the socket and fall down into the opening and inside the water heater casing to be lost forever Luckily, I am not speaking from experience here.

After replacing the cover to seal up electrical components, don’t forget to reattach the gas manifold and burner assembly you set aside earlier. Position the manifold tubing in position and insert the burner retainer bolt in place.

Hand tighten the manifold retainer nut. Tighten both nuts.

4. Inspect and Repair Faulty Water Heater Switch

Now, I had a number of things that could have been going on with our cold water heater. It was likely a bad electric heating element. The AC thermostat switch may have been bad. It certainly was after I shorted it out. I got a good voltage reading at the AC wall switch inside the rig. But see what I discovered when I investigated the last remaining electrical system component.

Since I was checking the whole electrical system anyway, I decided to test the toggle switch located on the front of the water heater. I was glad I did.

This small switch can be easily pried loose with a small flathead screwdriver. I discovered one of the connectors was fried. Whether or not this was causing our problem, it needed to be fixed. A good selection of connectors and fuses, or a through electrical connection kit, is a good thing for any RVer to have for just this very reason!

After cutting off and replacing the damaged blade connector and reinserting the switch, it was time for the moment of truth…

Open the pressure release valve on your water heater. Turn the bypass valve inside to allow water to flow back into the tank. Let water fill the tank until until it comes out the release valve. Shut the pressure release valve. Turn on electrical power to the water heater, and wait.

Within an hour, we once again had Hot Water! 🙂