@anon88169868, thanks for the manual. The regulator board is top left of page 79. On the bro-in-law’s boiler it is not installed, the 2 connectors are just sitting on the inner casing.
It is s simple implementation, just heating the water for a single circuit CH system.
It was set up such that it had to be set to “Manual” and would fire up until the internal temperature sensor matched the temperature set on the dial on the front panel. The burner would then shut down. If the room thermostat then switched on, all it would do is to start the CH circulation pump. As the CH water flows through the boiler, it cools it. The drop in temperature inside the boiler is sensed by its internal sensor triggering the burner to fire until the temperature set on the front dial is attained. That is how the previous owner had managed to bodge it into working.
I am trying to get it into a more economic mode of functioning without too much outlay. There is little point in spending money on such and old boiler, it would be better spent on a more efficient and cleaner system. They have a good woodburner in a central fireplace and electric AGA. They use this to keep the chill out overnight.
It’s not an unreasonable approach, you don’t have to have the pump running all the time and the burner will respond to demand, but won’t be lit if the return temperature is hot enough.
If not already wired as such I think that you need to make sure that the live connection to the boiler thermostat comes from the room thermostat so that there is no risk of the boiler firing without the pump running.
Older boiler control systems are incredibly simple.
Yep, that is how it is now. The room thermostat controls the lighting of the burner and the pump is running most of the time. If I can’t identify, and source, the DeDietrich control board I am thinking of putting the pump on a minuterie. That should provide a pump that starts up when the boiler begins its ignition sequence and a few minutes overrun when the room thermostat gets up to temperature.
I would put it back to how you describe the “bodge” with the pump controlled by the room thermostat and the burner by the room thermostat and the temp sensor in the boiler - that way the pump will not run all the time.
You could then power the whole lot via a timer.
I haven’t had chance to have much of a look at the boiler schematic. There’s usually a fan to draw air through the burner, possibly a pressure switch to confirm the fan is drawing air before starting the oil pump and ignition - what’s happening with those bits of the system?
Hi Paul, sorry I was not clear. Under the bodge the burner was not switched by the room 'stat. The boiler had to be set to “Manual” and was therefore on permanently. When the pump was running, water was circulated around the house, heating up the radiators. The boiler itself has a control to set the temperature of the heating water.
Under manual operation the burner ran until the water attained the temperature set on the boilers control panel. The pump alone was switched by the room thermostat. When the pump was off the boiler attained its pre set temperature quickly. When the pjmp came on, the circulation of water would bring colder water into the boiler. This would drop the temperature inside the boiler below its preset limit and it would fire up.
Without the pymp running, that internal temperature would slowly drop until it fell velow the limit and the boiler would fire again, until it reached the correct temperature. It would do that any time day or night.
I think I followed things well enough. 
Ideally the circulating pump would not be running unless the room needs heating, having the boiler firing without the circulating pump running is not that great - the risk is that the water boils in the heat exchanger damaging it.
A time switch is clearly a good idea but if you leave the circulating pump running it will consume power needlessly (as well as suffer extra wear but they tend to be pretty robust).
I’m not a heating engineer (my uncle was which is where I picked up the basics - albeit in the late 1970’s & early 1980’s) so don’t have masses of experience - just my own domestic set-ups.
I would, however, arrange things as I said above - time switch and room 'stat in series powering the boiler and its thermostat. That way the pump will only run when you actually need heat, not all the time and the boiler will only fire when the pump is running.