Have an error code flashing on your Planar heater? 

The heater sometimes takes a while to prime (purge the air from the fuel supply pipe) before it will fire up. If the heater is not being run often it will take longer to prime the system.
The heater will attempt to prime itself when you press the start/heat button on your controller, however it will only attempt to do this for a short time, possibly not long enough to successfully prime itself.
If you have an unsuccessful heater start, then try to start it again, often two or three attempts will be fine if the heater has been stood for a while.If, however, this method is not working then try removing the heaters power (fuse) for ten seconds, then put the fuse back in and press start, this will reset the heater fault.  
Notes:

• Keep the inlet and outlet uncovered, clean and clear of items that could fall into the vents
• The heater may not run if your diesel fuel tank (that the engine uses) is too low
• The heater may not run if the van is parked on an incline as the pickup may be above the fuel level
• Water, bio-diesel, petrol and dirt can cause issues on older vans, the fuel tank should be drained and cleaned out if you suspect contamination (we do not offer this) 
• To avoid technical problems with the heater, turn it on regularly - once in two weeks on maximum power for 30 minutes even in the summer. These simple steps will make using the heater straight-forward.  

Download a copy of the manual for your heaters controller.

PU-5 SIMPLE CONTROLLER

COMFORT CONTROLLER

PU-27 CONTROLLER (now discontinued)