Sorry it’s months since I looked at one but I’m sure its labelled as auxiliary heater or such like. Yes the system heats the water around the engine and allows this to use the normal cab heater to distribute the warm air. Once the pump seizes the heater over heats because the water doesn’t circulate and it cuts out. The pump is behind the o/s steps on a bracket behind the Heater unit, it vibrates gently when working.
eagerbeaver:
I reckon Colin is in for a night of ’ Maoster & Servant ’ if you know what I mean Tango
He’d love that 
Thank you Poleman for the suggestions. As for you other two muppets… 
Bit of pent up frustration there Maoster…
Get yourself over to Col and ’ work it off '. ( Lovely & warm in his cab ) 
Fur que!
poleman:
it vibrates gently when working.
It might not be the only thing vibrating now!
Check there isn’t any wires hanging off the fuel pump. We had a Daf CF where the night heater was dead, it had power but would not fire up. Turns out, there was two small wires that had come away from the top of the fuel pump on the diesel tank. These wires were key for the night heater to fire.
eagerbeaver:
I had the same yesterday mate! Thought it was me being a knob.Answers…we need answers…another thing; when you accidently touch the button with the clock symbol on it, how do you get the night heater symbol and the number 1 off the screen? Looks like I have ended up ’ setting ’ something.
Aaaaarrrghhh…
If you want to cancel a setting press clock button until night heater symbol flashes then change it with red or blue arrow button so it doesn’t flash then press clock button again, job done
Nice one Uncle! Does my head in when it won’t go off.
First press fire button and listen for pump clicking next to fuel tank.
Next check nothing blocking air inlet under bunk
Next most common fault glow plug fail easy fix new glow plug(even get the split socket to fit it)
Next common fault flame detector again easy fix buy a new one.
Next check for fan rotation (listen)
Glow plug is most likely as they dont like bio and the 10% in standard fuel buggers them up.
Now for a slaggin bring it on.
No slagging from me; you obviously know more about night heaters than I do tbh. It’s off to Merc today anyway so I’ll drink their coffee whilst they sort it. Thanks to everyone for their input.
the maoster:
No slagging from me; you obviously know more about night heaters than I do tbh. It’s off to Merc today anyway so I’ll drink their coffee whilst they sort it. Thanks to everyone for their input.
Hopefully won’t need a spare part from deepest darkest Germany to be shipped over what with the weather taking on a more chillier tone.
eagerbeaver:
Nice one Uncle! Does my head in when it won’t go off.
If you’ve got an iPhone or ipad there’s a free app called Mercedes Benz guide which gives a user guide on all merc models just download it and you can use it offline don’t know if it’s available on android though
bald bloke:
Hopefully won’t need a spare part from deepest darkest Germany to be shipped over what with the weather taking on a more chillier tone.
You men something rare like a filter or wiper blades
gardun:
bald bloke:
Hopefully won’t need a spare part from deepest darkest Germany to be shipped over what with the weather taking on a more chillier tone.You men something rare like a filter or wiper blades
My old company had a couple of Actros’s in the dealers for about 6 weeks waiting on some rare part to do with the clutch I mean where was this part coming from the moon !!
poleman:
There is a fuse in the n/s/lower foot well fuse box, if you pull it out and refit it after 10 seconds or so it will reset the night heater. These heaters suffer from injector, glow plug and water pump seizure failures. Most of the problems we saw were seized circulation pumps which pump the water around the heater pipes and engine pipes. If after removing and refitting the fuse it still flashes it needs to go onto the Mercedes computer.
Update; job sorted now, it was indeed a seized water pump which caused it to protect itself by shutting down. A watercooled night heater? Who’d have thought it? They’ve obviously come on a bit since the days that they were just a plastic box sat under the drivers seat!
I’m also planning on leaving it switched on until April at least (a bit like some people do with foglights).
the maoster:
poleman:
There is a fuse in the n/s/lower foot well fuse box, if you pull it out and refit it after 10 seconds or so it will reset the night heater. These heaters suffer from injector, glow plug and water pump seizure failures. Most of the problems we saw were seized circulation pumps which pump the water around the heater pipes and engine pipes. If after removing and refitting the fuse it still flashes it needs to go onto the Mercedes computer.Update; job sorted now, it was indeed a seized water pump which caused it to protect itself by shutting down. A watercooled night heater? Who’d have thought it? They’ve obviously come on a bit since the days that they were just a plastic box sat under the drivers seat!
I’m also planning on leaving it switched on until April at least (a bit like some people do with foglights).
A night heater that warms the engine? Do you live in Siberia?
Ce la vie.
the maoster:
norb:
The flashing light may be a flash code for the fault ,I know with the DAF with eberspachers ,the filter in the glow plug chokes upI counted the flashes Norb on the off chance it equated to a fault code, there’s consistently 10 long flashes followed by one quick one.
morse for DONALD. 
colds coming. 