Whale Space Heating System: Controls, Bleeding & Fault Diagnosis
A complete guide to Whale blown-air and wet central heating systems in caravans and motorhomes — understanding the controls, bleeding the system, diagnosing common faults, and annual maintenance.
What This Is
Whale manufactured a range of space heating systems for the UK leisure vehicle market, including the Whale Expanse (covered in a separate guide), the Whale Heating System (a wet central heating system using a gas-fired boiler and radiators), and blown-air systems that distribute warm air through ducts to habitation areas. The Whale wet heating system is less common than the Truma or Alde systems but is found in a number of UK-built motorhomes and caravans from the 1990s and 2000s. It operates similarly to a domestic central heating system — a gas boiler heats water which circulates through small-bore pipes to panel radiators or fan-assisted heat exchangers. The system uses a 12V circulation pump and a room thermostat. Blown-air Whale systems use a gas burner to heat an air heat exchanger, with a 12V fan distributing warm air through flexible ducting to outlet grilles around the vehicle. These are simpler systems with fewer components to maintain. This guide covers both types, with a focus on the most common owner-level maintenance tasks and fault diagnosis.
Tools & Parts Required
- Small flat-blade screwdriver
- Crosshead screwdriver
- Radiator bleed key (for wet systems)
- Small container to catch bleed water
- Multimeter
- Torch or head torch
- Gas leak detection spray or soapy water
- Soft brush for burner cleaning
Step-by-Step Instructions
- 1
UNDERSTANDING THE CONTROLS: Most Whale heating systems use a simple wall-mounted thermostat with a temperature dial and an on/off switch. Some later models have a digital display showing room temperature and set temperature. The thermostat controls the gas burner — when the room temperature drops below the set point, the burner fires and the circulation pump (wet systems) or fan (blown-air systems) activates.
- 2
ANNUAL INSPECTION — BLOWN AIR SYSTEMS: Remove the front cover of the heater unit (usually 2–4 screws). Inspect the burner for carbon deposits, spider webs, and insect nests — these are extremely common after winter storage and are the primary cause of ignition failure. Clean the burner ports gently with a soft brush. Check the igniter electrode gap (3–4mm) and clean any carbon from the tip.
- 3
Check all warm air outlet grilles around the vehicle. These should be open and unobstructed. Blocked grilles reduce airflow and can cause the heater to overheat and shut down on the thermal cut-out. Vacuum any dust and debris from the grilles and the ducting inlets.
- 4
Check the combustion air inlet and flue outlet on the outside of the vehicle. Both should be clear of obstructions. A partially blocked flue causes poor combustion, sooting, and potential carbon monoxide risk. Clean with a bottle brush if necessary.
- 5
ANNUAL INSPECTION — WET SYSTEMS: Check the system water level. The expansion tank (a small plastic reservoir, usually near the boiler) should be between the MIN and MAX marks. Top up with distilled water mixed with a small amount of corrosion inhibitor (use a caravan-specific inhibitor, not a car radiator inhibitor).
- 6
BLEEDING THE WET SYSTEM: Air in the system causes cold spots on radiators and a gurgling noise from the circulation pump. To bleed, turn the system on and allow it to reach operating temperature. Then, starting with the radiator furthest from the boiler, use a bleed key to open the bleed valve (small square fitting at the top corner of each radiator) until water flows steadily with no air bubbles. Close the valve. Work back towards the boiler, bleeding each radiator in turn.
- 7
Check the 12V circulation pump (wet systems). The pump is a small cylindrical unit on the return pipe, usually near the boiler. It should be warm to the touch when the system is running. If it is cold, the pump may have seized. Tap the pump body gently with a screwdriver handle — a seized pump sometimes frees itself. If not, the pump will need replacing.
- 8
FAULT: HEATER DOES NOT IGNITE. Check the gas supply — is the gas bottle open and does the regulator show adequate pressure? Try another gas appliance (hob, for example) to confirm gas is flowing. If gas is available but the heater does not ignite, check the 12V supply to the heater (fuse and wiring). If both are fine, the igniter electrode or gas valve is likely faulty.
- 9
FAULT: HEATER LIGHTS BUT SHUTS DOWN AFTER A FEW MINUTES. This is usually caused by one of three things: (1) a blocked flue causing the overheat thermostat to trip — check and clear the flue; (2) a dirty flame sensor (thermocouple) that fails to detect the flame — clean with fine wire wool; (3) a blocked air inlet restricting combustion air — check and clear the inlet grille.
- 10
FAULT: THERMOSTAT DOES NOT CONTROL TEMPERATURE ACCURATELY. First check the thermostat is not in direct sunlight or near a draught, which will give a false reading. If the thermostat is correctly positioned and still inaccurate, the thermostat sensor may be faulty. Replacement thermostats are available from Whale and caravan accessory suppliers.
- 11
FAULT: WARM AIR FROM SOME OUTLETS BUT NOT OTHERS (BLOWN AIR SYSTEMS). This indicates a blockage or disconnection in the ducting. Check each duct run for kinks, crushing (common under seat bases), or disconnected joints. Reconnect or straighten as required. Ensure all outlet grilles are open.
- 12
After completing any maintenance, restore the gas supply and test all gas connections with leak detection spray. Run the heater through a full cycle, checking for correct ignition, stable flame, and proper shutdown when the thermostat is satisfied.
Common Mistakes to Avoid
- Not bleeding the wet system after winter storage — air enters the system when it is drained and must be purged before the system will heat efficiently.
- Topping up the wet system with tap water only — always use distilled water with corrosion inhibitor to prevent scale and corrosion in the small-bore pipework.
- Ignoring the flue after winter storage — insects and spiders nest in flues during storage and this is the most common cause of ignition failure in spring.
- Blocking warm air outlet grilles with cushions or bedding — this causes the heater to overheat and trip the thermal cut-out.
- Confusing the room thermostat with a fault — if the heater shuts off after reaching temperature, this is normal operation, not a fault.
Safety Warnings
- IMPORTANT: Any work on the gas valve, gas injector, or gas pipework must be carried out by a Gas Safe registered engineer.
- Never operate the heater with the flue blocked or disconnected — carbon monoxide poisoning risk.
- Always test all gas connections with leak detection spray after any gas-side work.
- Do not operate the heater while the vehicle is moving.
- If the heater produces yellow or orange flames, soot deposits, or a smell of combustion gases inside the vehicle, turn it off immediately and have it inspected by a Gas Safe engineer before further use.
- Install a carbon monoxide alarm in the habitation area — this is strongly recommended and required by many campsites.
When to Call a Professional
Call a Gas Safe registered engineer if: the gas valve is faulty, the unit produces yellow flames or soot, you suspect a flue gas leak, the unit has not been serviced in more than 2 years, or the circulation pump (wet systems) needs replacing and you are not confident with 12V wiring. Annual gas safety checks are strongly recommended.
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