Having had a poke about t'internet with regards to your predicament I came across
this website. Based on your fault code they recommend the following solutions:
Fingers crossed for you they're not a cheap thing to replace.
Stage 4 Start failure.
Heater makes two attempts to start with no success and then stops completely, no smoke comes from the exhaust pipe or heater makes two attempts to start, may smoke for a while or smoke heavily and then it stops. Fault codes 52.
Eberspacher recommend servicing the heater annually so this would usually be our first step if the heater is producing smoke, especially if one had not been done recently, (see servicing pages for DIY servicing details).
White smoke is usually heated fuel and air mixture that has not been burnt, no smoke may mean no fuel is reaching the Eberspacher.
Check if you have run out of or are simply low on fuel, a tank pick up tube can be 50mm or more above the tank bottom. This ensures there will be enough fuel left to run the engine and prevents water and crud in the bottom of the tank from being picked up. As an example on one camper van the tank holds diesel for about 250 miles but the heater stops working after 200 miles.
If the fuel pipes were empty before starting check if purging of air is complete.
Check fuel is arriving at the heater, disconnect fuel pipe, fuel should squirt out on each pump stroke.
If there is no fuel look at the Fuel Supply Faults page.
Do the fuel quantity check, if the amount of fuel is insufficient -
Check the fuel lines and connections, fuel filter for air leaks and blockages. Check all clips are tight.
Check the fuel pick-up pipe, on some non Eberspacher types the tube pushes into the upper part and can have an air leak.
Check condition of rubber sleeves, they swell and can become porous as they deteriorate.
Check pipes butt together inside the sleeves, gaps can trap air bubbles.
Check pump has not been knocked or the fixing bolt become loose so pump is at an angle of less than 15 degrees. (see Fuel page)
Check for water in tank, water from condensation builds up in bottom of tank and it can be pumped instead of fuel.
Check if exhaust pipe / silencer or combustion air intake pipes are blocked, possibly with ice or water.
If a service is not done check the glow pin, clean ventilation hole above the screen in the glow pin chamber.
If the screen is removed check the fuel inlet hole is clear. It may also be worth blowing through the metal fuel pipe section from where the fuel pipe is connected to the glowpin chamber, it possibly may need an air compressor or a bicycle pump, before fitting the new screen.
Check fuel for degradation and floating debris, see fuel page.
Check also the
Eberspacher starts normally but stops whilst running, it may try to restart category as causes can be the same.
Good work. 
