Webasto heater

[burtty]

It starts up however after a short while an HS4 error code appears and the green power light on the power management system starts to flash

 

[oldiebut goodie]

Supply voltage too high. ( look in the heater manual )
If that is supposed to be h84 = voltage too low.
( Give more details of heater model and controller would help with understanding what you have rather than guessing ) Details of the power management system would help also.

 

[Dellmassive]

And add a few pics too if you can?

 

[burtty]

Thanks it was a power issue