The electric fuel pump makes a familiar “click... click” sound as it pumps fuel to the heater. It clicks faster depending on the heat required. The fuel pump is mounted inside a very soft rubber mounting ring which absorbs most of the vibration from the ‘pumping’ action. While most of the vibration is absorbed, some noise escapes. As the heater fan is so quiet when running on low, you may hear the pump clicking away in the still of night. The addition of sound deadening material around the fuel pump can deaden the faint pump noise almost completely.
It's been observed that if the installation does suffer problems, there is a good chance it's related to fuel supply - either a blocked fuel filter, because of dirty fuel and or other fuel related issues. Eberspacher don't recommend running the furnace, despite it being fitted with a filter, when refilling your diesel tanks. The obvious reason for this is that the contents of your tank are being stirred up and you may attract dirty fuel into the filter, which is quite small.
Switching the heater on for the 1st Time - How it performed
Running the heater for the first couple of times, you will get a little smoke coming off the stainless steel exhaust tubing, the result of lubricating oil used in the manufacturing process.
On my 10.6m RV, the cabin temperature took about 20 minutes to increase from 10 degrees C to a very comfortable 20 degrees C. The air temperature coming out of the warm air outlet (on full heat) gets up to 80C. Once the set point temperature was almost achieved, the blower speed starts to reduce, as does the amount of fuel used and the heat produced. When the heater dropped down to low mode and had settled into its 'sweet spot', the air temperature coming out dropped down to about 35 degrees C.
Even with an outside temperature of zero degrees, the heater continued to run on its lowest speed and fuel setting for about 50 minutes each hour. Occasionally, it gradually increases speed, for about 10 minutes every hour, once it senses it is losing the battle to maintain a delicious 20C degree cabin temperature. Then afterwards it dropped back to low mode again.
The furnace is well engineered and it is surprising how cool the plastic outer heater cover remains while the heater is running.
Running the heater without the muffler doesn't make a big difference to the noise level produced, I’ve been told it acts more as a spark arrestor.
This heater is not cheap, but it's also very well designed and both quiet and very efficient.
It’s very convenient to use if fuel is being supplied from your existing diesel fuel tank. You will hardly see a drop in your fuel gauge, unless you are using it 24 hours a day. Because of the 5,000 hour expected life cycle, you can install it and forget it (other than a few simple services along the way).
I’m very pleased with my purchased and highly recommend the Eberspacher product. The D4 is a great match for my size vehicle.