Paging "andrejuan" - 4-way vacuum valve

macplaxton
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Posts: 1,373

Paging "andrejuan" - 4-way vacuum valve Sept 20, 2016 15:04:23 GMT

Quote

Post by macplaxton on Sept 20, 2016 15:04:23 GMT

Info:

The black thing you see is a diode (such as a 1N4001). In this circuit it is used as a fly-back diode en.wikipedia.org/wiki/Flyback_diode

On a DAF 66 it isn't important and is omitted as the only switching that takes place is through mechanical switches (such as the brake light switch, the low-ratio hold and the carb microswitch).

Where it comes into play is on later Variomatics which have a Tachometric Relay box fitted. If the diode is omitted the reverse voltage spike toasts the switching transistor in the unit. (see www.wouternieuwlaat.nl/reparatie_tachorelais.htm ) In that article an extra diode is fitted to the Tacho Relay as belt-and-braces if the one in the 4-way vac valve is shot.

The other side doesn't have one as it doesn't have anything electronic to fry.

Also from memory the later 4-way vacuum valves need two earths as they aren't internally connected.

Last Edit: Sept 20, 2016 15:06:25 GMT by macplaxton

1972 DAF 44 Estate. Just the one DAF, honest.

andrejuan Bigger Belter Posts: 208	Paging "andrejuan" - 4-way vacuum valve Sept 20, 2016 19:43:21 GMT Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by andrejuan on Sept 20, 2016 19:43:21 GMT Interesting thank you, so presumably whilst it is omitted on the 66, it won't do any harm being there?

macplaxton Technical Advisor Posts: 1,373	Paging "andrejuan" - 4-way vacuum valve Sept 20, 2016 19:57:40 GMT via mobile Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by macplaxton on Sept 20, 2016 19:57:40 GMT Correct. The only thing you might have to do with a later vac valve on a 66 is to make sure both earth terminals are earthed.
	1972 DAF 44 Estate. Just the one DAF, honest.

Tuning Data
Model	Plugs gap	Points gap	Timing	In. valve	Ex. valve	Idle
33-> Jul'71	0.8mm	0.5mm	6 BTDC	0.1mm	0.15mm	725
33 Jul'71->	0.8mm	0.5mm	5 ATDC	0.1mm	0.15mm	900
44-> Jul'71	0.8mm	0.5mm	6 BTDC	0.1mm	0.15mm	725
44 Jul'71->	0.8mm	0.5mm	5 ATDC	0.1mm	0.15mm	900
55	0.6mm	0.5mm	TDC	0.15mm	0.20mm	700
55 Marathon	0.7mm	0.5mm	TDC	0.15mm	0.20mm	700
66 all 1108cc	0.7mm	0.5mm	TDC	0.15mm	0.20mm	725
66 1289cc	0.7mm	0.5mm	6 BTDC	0.15mm	0.20mm	725

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Paging "andrejuan" - 4-way vacuum valve

Post by macplaxton on Sept 20, 2016 15:04:23 GMT

Post by andrejuan on Sept 20, 2016 19:43:21 GMT

Post by macplaxton on Sept 20, 2016 19:57:40 GMT