Thermal Comfort - Blown Air Heating Systems for Motor Vehicles

Comfortable temperature is an important consideration when designing working or living spaces in motor vehicles.
Blown air heating provides interior temperature control, warmth and ventilation in all seasons.

Blown Air Heater Applications:

Leisure vehicles including camper vans, motorhome, caravans, van conversions, and boats.
Heating systems in live-in accomodation vehicles used for van life. Off-grid living area heating.
Buses, minibuses, to provide warmth and improve passenger comfort.
Commercial vehicles including Hgv truck lorry cab heating.
Welfare vans, utility service vans, mobile canteens, mobile shops, library and sales vehicles.
Construction plant cab heating for excavators, bulldozers, and quarry dump trucks.

How Blown Air Diesel Night Heaters Work

Key components of blown air heaters include:
Heater unit outer housing for attachment to blown air intake , outlet ducting and vents.
Electronic controller mounted in heater casing
Variable speed blower fan assembly
Combustion chamber, burner tube, atomisation screen and glow pin
Flame detection and overheat sensors
Ventilation ducting
Wiring harness
External controller which may include on/off switch , timer, temperature setting, and sensing.
Fuel pump and filter assembly
Fuel lines
Combustion air intake duct
Combustion exhaust tube (24mm or 22mm stainless flexible tubing)

Heater Operation

When the night heater is switched on a ticking noise may be heard as the fuel metering pump operates to transfer fuel from the supply tank and prime pressurised fuel to the heater.
The pressurised fuel is injected through an atomising screen creating a fuel mist.
A red hot glow pin initially ignites the fuel mist causing combustion and heat within a combustion chamber heat exchanger unit.
A speed controlled blower fan module sucks air into the night heater inlet then blows air across the exterior fins of the heat exchanger causing output of warm blown air which may be directed through ducting and vents. You may hear the speed of the fan turbine increase gradually during start up to full speed then gradually decrease as the heater shuts down.
Hot exhaust fumes produced inside the night heater combustion chamber during the combustion process are expelled safely outside the vehicle via the nightheater exhaust.
Combustion flame, blower fan speed, and blown air temperature are monitored by a control unit.

Temperature Control

Room temperature control setting is selected using a programmer, thermostat and controlled by temperature sensors.

Safety features

Onboard night heaters have inbuilt safety features to prevent diesel fuel being pumped to the heater if the flame is absent.

Startup, running , and shutdown is monitored and controlled by an electronic control unit (ecu).
Repeated failure to start may cause the night heater to enter a lockout mode preventing further operation until reset procedures, sometimes requiring diagnostic equipment, are undertaken.

Safety Recommendation

We recommend fitment of Carbon Monoxide detectors where any nightheater is fitted in a vehicle. The combustion intake and exhaust must be fitted so as to draw air and exit exhaust gases to the fresh air atmosphere outside of any enclosed area. Do not run night heaters inside built up environments without suitable exhaust gas extraction equipment.

Typical faults which may prevent heater operation.

Glow pin failure

Build up of carbon and deposits on the glow pin, or electrical failure of the glow pin. Test resistance using ohm meter (multimeter). Replace faulty glow pin with new.

Internal Carbon Deposits

Carbon build up may cause the heater to discharge excessive white smoke from the exhaust.
Build up of carbon inside the heater combustion chamber and glow plug screen may cause ignition or combustion faults. Excessive smoke from the heater exhaust indicates that the heater needs servicing.
Servicing will require fitment of new gaskets when reassembling the heater.

Power Supply Voltage

Electronic control units rely upon having a reliable power supply at the correct voltage and good electrical connections.
Low or excessive battery voltage level may prevent heater operation and cause error codes to be logged which then prevents heater starting.
Wiring and connection faults can also prevent the heater operating.

Low power supply voltage may cause the night heater to log an undervoltage fault particularly where a night heater has been wired to operate from an auxilliary battery split charge system in camper van conversions and the split charge system is not operating.
Battery voltage too high may log an overvoltage fault typically due to an overcharging vehicle alternator.
Check battery, electrical wiring harness looms, connections, and controls.

Fuelling - Excessive white or black smoke emission

Excess smoke emitted from the night heater exhaust is often caused by incorrect quantity of fuel delivery or poor atomisation of the fuel

Check Fuel supply faults - fuel filter blockage, air entering fuel system, fuel pump failure or incorrect delivery, atomisation screen.
Fuel pump failure may result from electrical faults, controller, wiring, connections.


Blower fan motor failure

Blower fan speed is controlled and monitored by the night heater ecu.

Ensure all pipework and ducting is kept clean and free of obstruction.
Blocked vent air intake can be a particular problem where the heater is mounted in a truck cab behind the driver's seat.
Crushed or damaged ducting or exhaust will likely cause overheat sensors to activate, shutting down and locking out the heater.
Night heater exhausts are often fitted under the cab or vehicle floor becoming susceptible to damage. Generally stainless steel.
Night heater exhaust fumes must not enter the vehicle cabin.
Where a night heater is mounted below the floor pan of the vehicle this can cause vulnerability to water and dirt ingress and damage to ducting.
Motorhomes, Camper vans, VW Transporter vans T5 & T6 etc, often have the night heater underfloor mounted, sometimes below the driver's seat causing particular vulnerability to damage and failure.

Heater Locked Out

Heater control unit may lockout after failed start attempts. Lockout will prevent heater startup attempts until error rectified and fault codes reset. Erasing of error codes from the heater controller memory is possible using manufacturers reset procedure, which may require connection specialised diagnostic tools.

Cab Night Heater Repairs Shropshire

We stock certain Eberspacher and Webasto cab night heater components in case of breakdown.
Local vehicle nightheater breakdown callout around Shrewsbury Shropshire & Mid Wales (UK) area .

Vehicle Night Heater Application

Night heaters combine quiet operation to provide warmth with fuel efficient operation without the need for the vehicle engine to be running.
May also be referred to as:
FBH : Fuel Burning Heater
Parking Heater

Night Heater Electronic Diagnostics

Specialised computer diagnostic equipment, software, and specific interface leads may be required to access 12v or 24v night heater diagnostic features.
for example:
Eberspacher EDITH
Webasto Thermotest
Connection of control unit diagnosis equipment may enable the heater to be run off the vehicle for bench testing.

Heater fault codes

Many night heaters have fault code diagnostic functions allowing in service testing should a breakdown occur.
Manufacturers provide a list of heater specific fault codes listed within workshop manuals.
Specialist night heater diagnostic equipment and software may be required to access.
Problems during start up or operation may cause the heater control module to log error codes and lock out preventing startup.
Fault code memory may need to be reset to allow system start.
Some night heater component faults may require removal of the heater from the vehicle to allow stripdown and rebuild.

Blown Air Heater Output

Night heater kits are available for 12v and 24v vehicles in a range of models and outputs to suit the volume and interior space to be heated.

2 kW blown air heater

A 2kW night heater is the most popular size for cabin heating applications in vans, lorry sleeper cabs, camper vans and motorhomes.

3-5kW blown air heater

3 to 5 kW air heaters are popular for applications including minibuses ambulances and motorhomes.

Certain catering vans use blown air heating to keep mobile ovens warm.

Above 5kW blown air heater

Heaters above 5 kW may be specified for heating of larger vehicle interiors such as Library vans, Buses, Cargo areas etc.

Vehicle Heater makes and models

Manufacturer: Autoterm

Supply a range of blown air heaters including Planar.

Manufacturer : Eberspacher
Popular blown air heater models include
Airtronic D2 D2L M2 S2 D4 D4 D5 D8LC

Manufacturer : Propex

Propex manufactures a range of LPG gas and mains powered heaters for installation in vehicle conversions, motorhomes and caravans
link to Propex website (opens in new tab)

Manufacturer: Truma
Truma produces a range of blown air and water heaters generally aimed at the caravan and motorhome leisure markets.

Manufacturer : Webasto
Popular models include Airtop 2000 , Airtop2000ST, Thermotop

Manufacturer : VVKB

Manufacturer : Planar

Manufacturer : Airo

Oem names are used for reference purposes only

Unbranded Diesel Heaters

Common knowledge exists that a wide range of relatively low cost unbranded diesel 'parking heaters' are widely available in the UK from online marketplaces.
These unbranded heaters are often of far east manufacture and of varying 'lucky dip' quality with sometimes difficult to source repair components should they fail.
Quality control appears to be the major problem with many 'chinese' unbranded diesel heaters causing premature failure.
Budget electronic designs may result in radio frequency interference (RFI) which can consequentially affect other critical components.
Excessive CO gas emission can also be detrimental.

Which is the right specification of heater for my vehicle?

Many factors affect the specification selection of a standalone heater to heat your vehicle;
Use of vehicle
Times when heat is required
Seasonal Use
Volume of air to be heated : Length (L) x Width (W) x Height (H) in metres = Cubic capacity in Metres cubed.
Number of air changes required - number of times doors will be opened per hour
Ambient outside temperature
Body construction material and insulation - insulated - uninsulated - double glazed - single glazed -
Any ducting required and temperature affect of direct hot air on load or personnel.
Power system voltage - volt drop due to cable length and conductor size
Means of control and access to control panel
Fuel supply : Stand-pipe in existing fuel tank. T connectors to fuel lines. Standalone fuel tank. Mounting position of fuel metering pump. Noise insulation of fuel metering pump.
Air intake and exhaust
Purchase budget
Cost of maintenance and service parts
Mounting position of heater to maintain serviceability - is additional protection against water, road dirt and weather conditions required?
If heater is to be mounted in a box consider blown air intake and ventilation output, combustion air intake and exhaust access for servicing and drainage

Tel: 07703 558610 for Auto electrical & Diesel Nightheater mobile breakdown service in Shropshire, and Mid Wales areas.