MY BRAEMAR th5X23E showing reset -05 heater is not working at all

It appears to be an Australian unit. We are in North America, so this link might work better for you. The first thing you can try is cutting the power for 5 minutes, AKA a 'power reset'.

https://www.google.com/search?q=BRAEMAR+BM320+reset

..

I recommend a mechanic to do

not a car and truck question

try the user manual

http://www.braemar.com.au/get-support/get-support/owners-manuals

the product specs
http://www.braemar.com.au/heating/ducted-gas-heating/ducted-gas-heating-product-range-a-specifications

We had the same problem in our Braemar TA522, failed to ignite, flashes ‘reset’, and shows fault code 07. Tried a few simple fixes over several weeks, could not resolve it. Then tried simply cleaning the two flame sensors (see photo) with a small piece of wet and dry paper, and the problem was immediately resolved! They are easy to access - remove the lid of your unit (turn power off first), and you will see these two sensors attached to the flame burners. Clean the right-angled rod at the bottom, apparently it builds up carbon over time. You don’t need to remove them, with a small piece of wet and dry paper you should be able to get underneath the burners to clean them.

I had the fault code 05 (spectrolink controller) recently on a Braemer TG420 ducted heater. The heater would start and cut out on high temp as the room fan was not starting. I checked under the house and found the cable fitted to the return air thermistor had been chewed. I repaired the section of cabling and restarted the unit and it worked fine. Fault Code 05 is to do with the Thermistor in the return air duct.

Look for the error code on the right hand side of the display above the zone section and below the actual temp displayed.... refer to:
http://www.braemar.com.au/PDFDocuments/Section8_ServiceTroubleshoot.pdf

The Braemar heater I have is wired directly to the control unit. The only way to reset the time is to turn of the heater for 5 minutes - the remote display should clear, and turn it back on (takes a minute for remote to come back on) the time will be flashing - use the Up and Down arrows to set the time, and SET button to set the day of week.

sim lock

If a used unit check under lid for a pressure hose no thicker than a pen , black or clear, look for splits or if disconnected reconnect