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Eberspacher FAQ and general questions


How often should I get my Eberspacher heater serviced?

Eberspacher recommend servicing heaters annually (average of 2000 hours), every two years if heater is only used occasionally. Annual maintenance can prevent the heater failing in use, usually when you most need it. Our pages give DIY servicing details of some models. Servicing of other Eberspacher heaters should be similar enough to these to enable you use them as general guides. Alternatively use a dealer, list of dealers is on Eberspacher's website. Very old heaters like D1L, D2L, D3L, D4L, D5L are probably better left alone if the heater is working well.


Can you recommend a good dealer?

We are independent of Eberspacher and do not have direct contact with dealers except when purchasing spare parts. Thus we are unable to recommend specific dealers but larger dealers usually deal with more heaters so may be  more familiar with your problem than some of the smaller dealers. A list of dealers is on Eberspacher's website. Eberspacher UK are actively working with all their dealers to maintain and improve standards of service. A new accreditation scheme has recently been implemented so you should ask if your dealer is accredited.


Where can I get Eberspacher manuals?

See our manuals page. If all else fails contact us.


How long are Eberspacher spare parts manufactured?

Eberspacher cease manufacturing spare parts after 10 years, thereafter parts will be available only while they still have old stock.


Can you repair my Eberspacher heater if I send it to you?

We do this part of the website as a hobby not as a commercial business. Our other interests take up a lot of our time so we do not repair or service Eberspacher heaters. Dealers provide that facility.


Can I make it quieter?

When the Eberspacher is switched on and it reaches maximum power there is jet like roar. It is not loud but could disturb adjacent campers or boaters, especially in quiet locations. The noise reduces as the heater power drops. Fitting an exhaust silencer does reduce the noise level and I consider one essential for my own use. The vehicle type silencer is not gas tight so should not be fitted inside boats, boat versions are longer, they are also more effective. The combustion air inlet produces a low level noise, fitting a silencer reduces it further. More details on silencers are on our buying advice and silencer autopsy pages. Silencers are also available to reduce the blown air noise, they are big.

If the heater has previously been turned on and left in standby by reducing the temperature setting it does not go to the highest setting when restarting so will be quieter. The clicking of the fuel pump may be audible inside the boat or vehicle and can be reduced by fitting one of the newer rubber clamps in place of the older type clamp. (see buying advice pages). Metal fuel pipe can transmit this noise throughout the boat via the fixing clips. Fit the pipe inside cheap 6 mm internal diameter hose and clip that.

Blower motor bearings can wear and become noisy.


The controller setting does not give good control of temperature. / Will changing my controller improve the air heaters performance and which controller is best?

Eberspacher temperature control is not precise and adjustments will be needed depending upon ambient conditions. Heaters fed from fresh air must have a remote temperature sensor to control temperature, and some other installations may benefit from one,  details remote sensor page. There are a range of modern controllers available, all control the heater in the same way so performance will be the same. Digital controllers make it easier to reset to the same required target temperature and usually have a separate on/off button. We prefer controllers like the 801 and some 701 versions, these have diagnostic read out and reset facilities which can be extremely useful.


Can I fit a modern controller to my old Eberspacher air heater?

They can be used with D*LC and D*LCC models but ventilation modes may not work. Modern air heater controllers are not compatible with older heaters which use a thermostat like D1L, D2L, D3L etc.


Can I fit an old controller to my modern air heater and which wires should I use?

A rheostat controller will work with Airtronic heaters but will not give the ventilation function. Wiring details are on the wiring and controllers pages. Most older controllers were thermostats which are not suitable for modern air heaters. We have no data sheets on older controllers and no idea on wiring details.


Can I remove the 1 hour limit on my 701 controller.

Eberspacher 701 timers with a white logo are limited to 1 maximum on time. We do not have one and I do not know of a modification to increase this time but the 701 on/off can be manually bypassed with a simple switch. Details are on the controllers page.


Can I add a second controller to my Eberspacher?

Yes by using a switch to select the active controller, see twin controllers page.


Can I add a second remote sensor?

Yes by using a switch to select the active sensor, see remote sensor page.


Which type of heater is best Water or Air?

If the answer is not obvious you should talk to dealers or other Eberspacher users. Air heaters will not provide hot water. Water heaters on vehicles are usually installed by the manufacturers. Adding a water heater to a modern vehicle's engine water supply can cause problems, see the water heater introduction page.


What is the difference between a D4 and a D4 Plus?

The D4 Plus has a more powerful fan so can have longer air ducts.


What is a fan matrix?

A fan matrix is similar to a vehicle radiator, hot water flows through it and a fan blows air through transferring heat to the air. This allows water heaters to give hot air outputs as well as a hot water supply


My Eberspacher heater has stopped working, is it the ECU?

Unfortunately our crystal ball does not work very well these days, it is probably getting old, just like me! There are many reasons Eberspacher heaters fail to fire up. It might be the ECU is faulty but more often it can be due to many other causes. Eliminate these first as a new ECU is extremely expensive. See our faults page for guidance and diagnosis.


What fuel is best?

Eberspachers are designed to run on several types of fuel. See the manual or our Fuel pages. If the fuel is fed from the main engine tank that will determine your choice. For a separate tank Kerosene (28 second central heating oil) is the fuel we personally use. Derek ran his D2 on it for about 8000 hours, many of them on about 12 hours continuous low heat and it is still showing no signs of needing a service.

An Eberspacher technical representative told us that the Ultra Low Sulphur Marine Gas Oil burns almost as clean as premium kerosene (paraffin) so he advises it is not worth fitting a separate tank for kerosene.


Can the Eberspacher be altered so it does not automatically switch into standby?

Can the Eberspacher be controlled non automatically?

This request is usually asked because there is such a large temperature difference between when the unit switches into standby and when it restarts. The reason the heater switches into standby is simply if it kept producing heat the temperature would continue to rise. There are no manual override settings. Personally I would like a manual control on my van. When I spoke to Eberspacher they explained that there were no manual settings for two reasons. 1 If the heater is used continuously on low heat the burner will clog up, high heat burns off most deposits. 2  If the heater is used on one setting the flame always hits the same point on the burner tube, distorting it. Circumvention of the automatic control will void the guarantee.

One way to keep the ambient temperature below the switch off temperature is to open a window allowing more heat to escape, unfortunately my van windows are not accessible from the back. Another idea could be to fit a controllable splitter in the blown air duct and vent part of the heater output outside. I have produced a prototype DIY automatic splitter for this purpose, details will be added to the website later.


How can I increase the amount of heat?

Adding more insulation to the area will reduce the heat losses. If air ducting is long and passes through areas like lockers that do not need heating insulate the outside of the duct to reduce losses. An item like http://www.screwfix.com/p/thermawrap-loft-insulation-400mm-x-5m/76477 looks a good solution. Changing from fresh air supply to recirculated air would give more heat but can cause problems with condensation. We have met instances where people expect a heater like a D2 to heat a large boat. A D2 for example will supply 2000 watts so may be too small, upgrade to a larger heater like a D4. A D4 is physically larger and the ducting has to carry twice as much heat so its diameter will often need increasing.


My heater seems to take a long time to reach maximum heat.

The heater should reach its maximum heat output in under 5 minutes. It can seem a lot longer than that especially if the heater is only just large enough to cope. If the air ducts are long and unlagged through cold areas they can absorb the heat increasing the time taken for maximum heat to reach the outlets. See also previous item.


Where can I get Eberspacher heaters or parts cheaply?

The words 'Eberspacher' and 'cheap' are usually not related. Personally we use Ebay for most of our purchases. Please donate your faulty or unwanted parts, they help to improve our knowledge.


What are the minimum and maximum Temperature settings on controllers?

Information from Eberspacher documentation is contradictory.  One document for the D2 gives +10 to +30 degrees, the 801 controller gives 5 to 32 degrees C. Another document gives 47 to 97 degrees F (8 to 36 degrees C). Below this lower limit the heater will switch to maximum heat setting. In general the lower limit is only important where the heater is fed with fresh air without a remote temperature sensor.

The upper limit is higher than required for normal use so is unimportant.


What is the temperature of the heated air?

The temperature of the air passing through the heater on Boost setting is raised by about 175 deg F (80 deg C). A temperature probe held in the heated air close to the heat exchanger near the outlet on boost with no extra ducting fitted generally measures between 180 and 220 deg F.


What is the efficiency of the heater / Why is so much heat lost in the exhaust?

Gasses from the burning process are very hot. The heat exchanger absorbs part of this heat but some is still in the exhaust gas and this is wasted heat. A heater advertised as say 4kW outputs 4kW, it generates more heat than the 4kW to allow for losses through the exhaust.

Eberspacher air and water heaters are typically 84 to 86% efficient, ie only about 15% of the heat generated is lost. We measured the temperature of the exhaust gasses from a D2 on high power with no exhaust pipe fitted and an ambient temperature of about 10 deg C. A temperature probe held across the outlet pipe in the centre of the flow was about 440 deg C maximum. The metal surface of the exhaust outlet pipe both outside and inside measured with an infra red thermometer was about 105 deg C, just over the boiling point of water, a lot cooler than we expected.


I have some documentation that says heat exchangers need to be replaced every 10 years but no-one seems to do this.

Very old Eberspacher models like the D4L, D7L had a heat exchanger made from steel and after prolonged use could fail due to metal fatigue. Replacement after 10 years was made a legal requirement, presumably in Germany, I do not know if it applied to the UK. This law has never been changed. Later models have heat exchangers made from alloy which do not suffer this type of failure so it is ignored. Eberspacher UK do not know of any such failures on later models.


My heater has H-Kit on the label, what does this mean?

This label is on heaters from Summer 2008 to show it has a new version ECU which is compatible with the optional high altitude kit. This kit is only fitted to heaters working for long periods above 1500m, not needed for anywhere in the UK as it is not high enough. These heaters are also compatible with EasyStart controllers.


Can the Eberspacher heater be used while the vehicle / boat is moving?

Yes, ensure the exhaust and combustion air inlets are not pointing in the direction of travel and are not obstructed.


When replacing a bullet fuseholder with a modern blade type you advise replacing the 16 amp ceramic fuse with a 30 amp blade type fuse, surely it is dangerous to increase the rating?

Fuses are just a piece of thin wire which heats up as current passes through, when it gets too hot the wire melts and the fuse blows. Choosing a fuse rating is usually not an exact science as they are intended to blow only under fault conditions. If the rating is set to low it can blow when there is no fault, if it is too high wires could burn out and cause a fire. A fuse rated at 16 amps is designed to carry 16 amps without blowing, above that the higher the current the faster it will blow. A further complication is caused by the heat in the fuse and fuse holder building up with time which can delay the point at which it fails. 16 amp slow blow ceramic fuses were fitted as standard on earlier model heaters. These take about 20 amps while the glowpin is on. The thermal characteristics of that type of ceramic fuse allowed the fuse rating to be less than the actual current for that length of time. If a 16 amp blade type fuse were fitted it might blow. A 30 amp rating is normally recommended. Use a high quality blade type fuseholder. Cheaper low quality fuseholders are not suitable for high current equipment and may burn out or cause unreliable connections.


Your site url letonkinoisvarnish.uk is missing the familiar .co   how is that done?

We were one of the early websites which took advantage of the release of new domains including ".uk" in 2014. It was a first for both us and our website host technicians but by using a '501 permanent redirect' we were able to get anything going to our old site letonkinoisvarnish.co.uk redirected to letonkinoisvarnish.uk and also most importantly to transfer the original web rankings.

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