There’s a switch on the dash that says battery guard reset and I have to press it every five minutes because it keeps cutting the battery off, anyone know how to switch it off?
I thought those were only supposed to cut in when the battery voltage dropped to a certain level. You leave something on accidentally overnight, battery voltage drops, it kicks in, you arrive in the morning, press the button and its left enough juice to start it.
Check your battery voltage with a volt meter when the battery guard has cut in… Either:
A: Its working correctly and your battery voltage is 24.2V or less- and its saved your ■■■ by leaving enough power to start the engine. In this case you need new batteries
B: Your alternator is up the creek, not providing a full charge and therefor it cuts in quickly - i.e. if it floats at less than ±28V when running
C: The battery guard system is up the creek
Simples. (Meerkat squeak) 
I was given this lorry this morning and I was after driving it for two hours but left the sat nav and the daylight running lights on when being unloaded so I’d say the batteries are low and it probably did save my ■■■. Does the night heater use much power?, I might have to sleep in this lorry tonight.
jay0:
I was given this lorry this morning and I was after driving it for two hours but left the sat nav and the daylight running lights on when being unloaded so I’d say the batteries are low and it probably did save my ■■■. Does the night heater use much power?, I might have to sleep in this lorry tonight.
Your night heater shouldn’t affect it if all is ok
If your DLRs are LEDs then they also won’t affect the system,and the sat nav shuldn’t really affect it …
As you no doubt know by it’s name ,it is there to protect the batteries so you can start
Best bet is to get the batteries checked ,most workshops should have a tester that will print out the state of the batteries ,as in it will say replace battery.Also we are at the time of years when batteries take more of hammering
Get rate of charge checked
If you do a lot of town driving with multi drop then obviously the batteries may never get fully charged
Also lights left on for a couple of mins will trip it anyway
The night heater only draws power from the batteries to fire the glow plug on initial start up, if you have it on low all night it may keep stopping & starting which would draw more power rather than being left on all night at a constant chat.
I’d be getting the batteries checked ASAP.