Here’s what most RV owners don’t realize until they’re trying to sell: neglected mechanical systems tank resale value faster than almost anything else. A rig with clean cosmetics and a history of deferred maintenance sells for thousands less than one that’s a little road-worn but mechanically solid. I’ve bought plenty of both. The water heater is one of those systems that people ignore right up until a cold shower forces the issue — and on the Highland Ridge Open Range 308BHS, a failing thermostat is one of the most common culprits, causing the unit to either run scalding hot, refuse to heat at all, or trip the high-limit switch repeatedly until someone actually addresses the root problem. If you’re sitting with a water heater that won’t behave, this guide will walk you through the thermostat replacement the right way — not the “get it working well enough to sell” way, but the way that actually fixes it.
The Thermostat That Stops the Guessing Game on Highland Ridge Water Heaters
On the 308BHS, a failing water heater thermostat doesn’t always kill the flame — it just stops regulating temperature, leaving you with either scalding water or a tank that won’t heat past lukewarm. This is the OEM-equivalent replacement that actually holds setpoint without drift.
What works
- Temperature holds steady once set — no more creeping up to 160°F or dropping to 100°F on its own.
- Direct fit into the existing bracket; no adapter hunting or modification of the mounting plate.
- Burner cycling becomes predictable again — you’ll actually hear it kick on and off at consistent intervals instead of running continuously or staying dead.
What doesn’t
- Amazon’s estimated delivery can slip; order this before you’re actually out of hot water, because you’ll be showering in the campground bathroom for three days otherwise.
- Installation requires draining the tank fully — if your drain valve is stuck or corroded, you’ll be wrestling with that problem first before you even get to the thermostat swap.
I second-guessed this part once when I realized the tank was still warm and I couldn’t fully drain it — had to heat it up to boiling first just to get pressure equalization. View on Amazon
Signs Your 308BHS Water Heater Thermostat is Failing
Before you order a replacement, make sure the thermostat is actually the problem. Water heater issues can stem from several places, but a bad thermostat has some distinctive telltale signs. If your water temperature swings wildly — scalding one minute, then dropping 20 degrees the next — that’s classic thermostat drift. The same goes if the burner won’t stop running even after the tank reaches temperature, or if it won’t start at all despite fuel flow and ignition working normally.
Another dead giveaway on the 308BHS is repeated high-limit switch trips. The high-limit is a safety device that shuts down the burner if the tank gets too hot, but a thermostat that’s stopped reading correctly will let the temperature climb unchecked, triggering the cutoff over and over. You might also notice that adjusting the temperature dial does nothing — or worse, makes things worse. A good thermostat should respond immediately to dial adjustment with audible burner cycling changes.
How to Replace the Thermostat on Your Highland Ridge Open Range 308BHS
The actual replacement process is straightforward if you follow the right sequence. Don’t skip steps just because you’re impatient — a missed detail here will cost you more time than doing it correctly in the first place.
Step 1: Drain the Tank Completely
Turn off both the water supply and the water heater power. Turn off the propane as well if it’s a gas unit. Locate the drain valve at the bottom of the tank — on the 308BHS, it’s usually toward the rear lower corner. Open it fully and let the tank drain into a bucket or directly outside. This step is non-negotiable. The thermostat sits inside the tank well, and you cannot safely access it without full drainage.
If the valve won’t budge, try wrapping a warm wet cloth around it for a few minutes to loosen corrosion. If it still won’t turn, you may need to drain via the hot outlet line instead — disconnect it at the top of the tank and let gravity do the work. Plan 30 to 45 minutes for complete drainage depending on tank size.
Step 2: Remove the Access Panel and Locate the Thermostat Well
Most RV water heaters have an access panel that covers the thermostat area. On the 308BHS, this is usually a simple metal plate held by a couple of bolts. Remove those bolts and set the panel aside. You’ll now see the thermostat well — it looks like a thin metal tube extending down into the tank. The thermostat probe slides inside this well, and the electrical connector sits at the top.
Step 3: Disconnect the Old Thermostat
Before touching anything, take a photo of the wire connections so you know exactly how to reinstall the new one. The connector usually has two or three wires. Gently pull the connector apart — they’re designed to separate easily, but don’t yank on the wires themselves. Once disconnected, you can gently slide the old thermostat probe up and out of the well. It should come free without force.
Step 4: Install the New Thermostat
Slide the new thermostat probe into the well slowly and steadily. Make sure it sits fully and bottoms out — this ensures accurate temperature sensing. Reconnect the wires to the terminal block, matching the configuration from your photo. The connection should be snug but not forced. Double-check before moving on: loose wires here will cause erratic behavior or complete failure.
Step 5: Refill and Test
Close the drain valve, then slowly open the water supply inlet. Watch the tank area for leaks — you want to catch any before pressurizing. Let the tank fill completely. Once full, open a hot water tap at a sink inside the RV to bleed air from the lines, then close it. Now turn power and propane back on and set the thermostat dial to your desired temperature, usually around 110-120°F for daily use.
Listen for the burner to ignite within a minute or two. Once it does, let it run for 15 to 20 minutes while you monitor the water temperature at a nearby hot tap. The water should gradually warm. After reaching setpoint, the burner should cycle off. Adjust the thermostat dial up and down slightly — you should hear immediate burner response with each change. If everything behaves predictably, you’re done.
Common Mistakes to Avoid
Don’t attempt this repair with a full or partially full tank. Water weight makes the tank hard to work around, and you risk scalding if you accidentally breach something. Always drain completely first. Don’t reconnect power or propane until you’ve refilled — running a dry or nearly dry heating element will damage it fast.
Avoid forcing the thermostat probe into the well. If it doesn’t slide smoothly, something is wrong — a bent probe or debris in the well. Stop and investigate rather than breaking the new part. Also, don’t assume the old temperature dial setting will work on the new thermostat. They often have slightly different ranges. Start low, let the tank heat, and dial up to your comfort zone.
Why This Matters for the 308BHS Owner
A water heater thermostat replacement is a weekend project, not a roadside breakdown. It costs far less than a full tank replacement, and it restores one of those systems that quietly keeps your rig livable. On resale day, a mechanically sound water heater — one that actually holds temperature and cycles predictably — signals to buyers that the rest of the rig has been maintained too. That perception pays dividends when you’re pricing the unit for sale.
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