Alde RV Heater Problems: No Heat, Faults and Glycol
On this page (11 sections)
The Short Answer: An Alde Compact 3020 that will not heat at all is most often short of 12-volt power, out of propane, or set for electric heat with no shore power. Read the panel’s fault message first. Gurgling, cold convectors or “Overheat red fail” usually mean air or low fluid in the glycol loop, and a dripping safety valve points to the fresh-water tank.
How the Alde system makes heat and hot water
The Alde is not a standalone water heater. It is a small boiler that heats two separate liquids. Glycol fluid circulates through the coach’s convectors in a sealed, low-pressure loop with an expansion tank at the highest point. Fresh water sits in a built-in tank of about 2.2 gallons (8.4 liters) and is heated by the glycol around it. Alde’s US manual says the propane burner can produce around 3 gallons of 104°F water every half hour.
That design means a fault that stops the boiler stops both space heat and hot water, while a fault on the fresh-water side can leave the coach warm and the taps cold. Knowing which circuit is involved tells you who to call and how urgent it is.
| What you notice | Probably involves | Urgency |
|---|---|---|
| No heat and no hot water, fault message on the panel | Boiler supply: 12 V, propane, or 120 V | Read the message; see the table below |
| Coach warm, taps cold | Fresh-water supply or bypass | Owner checks below |
| Gurgling in the expansion tank, only the first few feet of pipe get warm | Air in the glycol loop | Bleed soon; do not run on high power |
| “Overheat red fail” on the panel | Air pockets or low glycol | Stop, let it cool, check level |
| Glycol level keeps dropping | Leak at a joint, drain cock or bleeder screw | Find it before the next trip |
| Colored, slightly sweet-smelling fluid under convectors or the boiler | Glycol leak | Clean up; book a repair |
| Clear water dripping from the safety/drain valve hose under the RV | Lost air cushion or high water pressure | Low, but check pressure |
| Water at the taps much hotter than usual | Normal when heating demand is high; extra hot water mode | Use a mixing valve; scald risk |
| Fresh-water leak after cold storage | Frost damage to the tank or fittings | Shut off water; technician |
Read the panel first
Alde’s panel shows fault messages only in standby mode. Wake the panel, return to the standby screen, and note what it says. These are the messages listed in the Alde Compact 3020 operating instructions (opens in a new tab):
| Panel message | What Alde says it means | What to do |
|---|---|---|
| Low battery | 12-volt supply has dropped below 10.8 V. Other false error messages can follow. | Charge the battery or check the converter. Clears at 11 V. |
| Gas failure | Out of gas, or gas is not igniting | Check the cylinder, try another full propane cylinder, check that valves are open and the regulator is not frozen |
| Fan restarts / Fan failure | Exhaust fan speed incorrect. Repeated faults become Fan failure. | Fan restarts needs no action. Fan failure that returns after a reset: dealer. |
| Overheat red fail | Overheat protection tripped, often from air in the glycol | See the glycol sections below |
| Overheat PCB | Failsafe triggered | Check glycol level and that the boiler compartment vents are clear and not packed with stored items |
| Heater not found | No communication between panel and boiler | Cable between panel and boiler; dealer if it persists |
| Panel failure | Moisture trapped in the control panel | Alde says to remove the panel and dry it overnight in a warm, dry place |
| Window open | Optional window sensor triggered; gas heating suspended | Close the window |
To reset some faults, Alde’s instructions say to switch off the heating at the panel, disconnect the RV from 120-volt power, and disconnect 12 volts from the boiler, then restart. Do this once after you have corrected the cause.
No heat on propane
Alde’s checklist for a boiler that will not start on gas is short and owner-safe:
- Is there propane in the cylinder? Other propane appliances, such as the stove, are a quick test.
- Is the main cylinder valve fully open?
- Is the boiler getting more than 11 volts DC? A weak battery is the most common hidden cause, especially overnight when the boiler and pump run on battery alone.
- Is the boiler’s 12-volt fuse intact? (The manual lists a 3.15-amp fuse.)
After a cylinder change or a long period of storage, Alde notes that the burner can take longer than normal to light. If it still reports Gas failure after these checks, a technician needs to look at the gas supply and burner. The safety page covers what to do if you smell propane or a CO alarm sounds.
No heat on electric
The electric element only works when the RV has 120-volt shore or generator power and electric heating is selected on the panel at a power level the incoming supply can carry. Alde’s instructions list these owner checks: confirm 120 volts reaches the RV, confirm the 120 V symbol shows on the panel, and listen for a faint click from the boiler relays when you switch the element on. Do not open the boiler to check the element; Alde warns that the 120-volt service is a shock hazard.
Coach is warm but the taps are cold
If the convectors are hot, the boiler works and the problem is on the fresh-water side:
- The fresh-water pump is off, the tank is empty, or city water is not connected.
- The Alde’s combined safety/drain valve was left open after draining for storage.
- The RV’s winterizing bypass is still set so water skips the heater.
- You are drawing hot water faster than the small tank recovers. Alde’s “extra hot water” setting raises the water to about 149°F for 30 minutes to stretch a shower; mix carefully at the tap.
Air in the glycol and overheat faults
Alde’s manual describes air as the usual cause of overheat faults: running the boiler at high power with air pockets in the loop can trip the overheat protection (shown as “Overheat red fail”). Other signs are heat that stops 2 to 3 feet from the boiler and gurgling in the expansion tank after the system was refilled. Small bubbles in a freshly filled system are common; Alde says stopping the circulation pump for a few seconds often clears them, and if not, bleed the system.
North American Alde systems have an automatic air vent, and Alde gives owners a bleeding procedure in the operating instructions, including tipping a trailer front to back so trapped air moves to the bleeder screws. The key points from that procedure: switch off the circulation pump before opening any bleeder screw (opening one with the pump running pulls air in), and use the bleeder locations shown in your RV maker’s manual. For an overheat fault, Alde also says to check the glycol level, confirm the pump responds, and wait 15 minutes for the fluid to cool before restarting. If the fault comes back after bleeding, a dealer should check the pump and sensors.
Glycol level, type and leaks
With the system cold, the fluid in the expansion tank should sit about half an inch (1 cm) above the minimum mark. Alde’s requirements for top-ups are specific:
- Use ready-mixed propylene glycol boiler antifreeze with inhibitor, meant for aluminum heating systems.
- Do not mix different types of glycol; Alde warns that mixing can make the fluid coagulate.
- Replace the glycol every second year so the corrosion inhibitor stays effective.
Small losses over time can be evaporation. A level that keeps falling means a leak, and Alde lists the places to look: joints, drain cocks, and bleeder screws. Clean up spilled glycol thoroughly and keep children and pets away from it. Persistent leaks and fluid changes are a reasonable job for an RV technician, who can also fill and bleed the loop with Alde’s filling pump.
The safety/drain valve is dripping
The fresh-water tank has a combined safety and drain valve, usually with a hose through the floor. The tank is designed to keep a pocket of air at the top that absorbs pressure surges from the water pump. Alde says to renew that air cushion after 10 days of use by briefly opening the safety/drain valve, or by draining the tank. Without the cushion, normal pump surges can make the valve weep.
High supply pressure is the other cause. Alde lists 44 psi as the maximum pressure for the hot-water side, which is lower than many campground taps. Use a city-water pressure regulator that keeps the RV within that limit. If the valve drips constantly at normal pressure, or will not close after you operate it, it needs replacing. Never plug the valve or its hose.
Very hot water: Alde heats the fresh water and the glycol together, so tap water can get very hot when the heating demand is high or extra hot water mode is on. Alde recommends a mixing valve set no higher than 118°F.
Frost damage
Alde’s instructions say to drain the fresh-water tank whenever there is a risk of freezing and when the RV is not in use, and that the warranty does not cover frost damage. The glycol loop is protected by its antifreeze; the fresh-water tank is not. If water appears around the boiler after cold storage, close the water supply, switch the boiler off, and have a technician inspect it. A split fresh-water tank in the boiler is usually a boiler replacement.
What the RV technician will check
A technician with Alde training checks supply voltage at the boiler under load, the fuse and wiring connections, propane pressure at the appliance, the igniter and flame detection, and the exhaust fan. For communication faults they check the panel cable and boiler circuit board; for glycol problems they look for the leak, then fill and bleed the loop. The RV hub covers other RV water heater brands if your coach has a separate tank heater instead.
Frequently Asked Questions
Q: My Alde worked during the day but showed faults overnight. Why? A: At night the boiler, pump and other loads run on the battery. When the voltage sags, Alde says the gas burner cuts out below 10.5 volts and “Low battery” appears below 10.8 volts, sometimes with other misleading messages. Fix the charging or battery capacity before suspecting the boiler.
Q: Can I top up the expansion tank with plain water? A: Alde specifies a glycol and water mixture. If you mix your own from concentrate, Alde gives 60 percent distilled water and 40 percent glycol, with more glycol (up to 50 percent) where temperatures fall below -15°F. Plain tap water dilutes the antifreeze and inhibitor.
Q: Can I run the Alde with the fresh-water tank drained? A: Alde says the system can heat the RV without the hot water tank filled, and no settings need to change when only hot water is required in summer. What you should not do is leave water in the tank when it may freeze.
Q: Is the Alde hot water safe to drink? A: Alde’s manual says the hot water from the boiler is not intended for drinking or food preparation. Use cold water for that.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Alde Compact 3020 operating instructions (US/Canada) (opens in a new tab)Alde Compact 3020 heating system in North American RVs; fault messages, voltage limits, owner checks, glycol care, bleeding, air cushion and pressure limits.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
- CPSC: carbon monoxide fact sheet (opens in a new tab)Carbon monoxide hazards and emergency response.
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