Looking at the picture of your edge connector (earlier in this post), I notice you have a wire connected at pin 12. On later dashboards that incorporate BOD pin 12 connects to the high oil pressure switch but you say you don't have a second oil pressure switch. I also notice that the wiring colour codes seem odd from pin 8 to pin 13 and I will need to check my manual to try and identify which year model dash your van actually had fitted at new. (The DOPS system has been found in vans manufactured around mid '85)
OK, if you are absolutely sure you don not have a second oil pressure switch (near the water pump )then you can do either of the following:-
1. Connect PIN 12 to earth and ensure that PIN 13 connects to your oil pressure switch (near the push rod tubes). Question is - why do you have a wire at pin 12 and where does it connect too at the moment?
2. Remove or disconnect the BOD PCB as it is doing absolutely nothing at the moment other than triggering the Buzzer. Removing or isolating it will not stop your tacho functioning. Without the BOD you will need to have the oil pressure LED function directly off the low oil pressure switch (as in pre 86 vans). The BOD connector that needs to be removed is shown below and is left disconnected once one of the mods descibed below is carried out..
(a) Replace the oil pressure led with a 12v type (Available as a RED flashing type or standard red) and place a wire link in the vacant connector in the postion occupied by the resistor as shown below.
(b) Keep the existing non flashing Red LEd and insert a resistor of any value between 470 (min) and 1500 (max) as shown below.
