oil pressure gauge (wiring)

[kieronriley]

hi ive been back on the boat today and wired the water light up.
now i have taken a look at the engine wiring hope i can explain this good enough for someone to understand,
on the back of the ignition switch there are four conections numered 1/4 a wire goes from no.3 to a block connector and from this there are three wires one going to the temp warning light then to the sesor,the second goes to the oil pressure sender then to the oil light and then on to earth and the third to a push pull on off switch then on to the ignition light then to the alternator,would i be correect in my thinking that the oil light should be wired in the same way as the water temp light,ie live to bulb then on to sender then earth,and if not could anyone tell me how to do it correctly.ande what is the switch for on the ignition light.thanks all in anticipation,Kieron

 

[VicS]

If there is no power to the ignition warning light the alternator will probably not start to generate ... (that is not, however, suggesting that switching the supply to the light off will stop the alternator generating once it has started)

Your oil pressure light can be wired like the temperature warning light or as it appears to be at present.

It is common for the positive supply to go to the light(s), the other terminal of the light(s) to go to the sensor(s) and then to earth.
Often there is no second connection on the sensor for an earth as the common ( automotive) arrangement is for the engine block to be the earth. In that case there is no alternative but to wire positive to bulb then bulb to the only terminal on the sensor.

 

[Billjratt]

Seems to be correct to me. All warning lights and/or buzzers will be fed by a common positive via the "ign " switch.
Each will then be grounded by their individual sensor switch except for the alternator ch light which is initially grounded by the field coil, then goes out as the field voltage rises to battery level. There has to be a historical reason for the switch in the alt circuit , as there would normally only be the "ign" switch in that circuit.
Personally, I'd get rid of it, as it's just more to go wrong. Perhaps the original owner had a manual method of controlling charging which has since been removed.

 

[kieronriley]

wirring

hi marsupial thanks.eveything works but that is after i rewired the water temp light yesterday after some advice on here,i am now wondering if the oil pressure should be wired in the same way as the temp light i.e live to light then on to sender and earth,and i just also wondered what the toggle switch on the ignition light is for .thanks,Kieron

 

[pampas]

a lot of small HP engines have the alternator switched to allow engine to run up to speed before exciting the rotor, usually done via the oil light cicuit eg, some Petter engines. If you are happy with your present system leave alone, if not go from the ignition s/w to the lamp.

 

[kieronriley]

wirring

hi pampus ,yes you are correct it is a petter mini twin and i have heard some time in the distant past that the alternator was wire through the oil swtch but could not and still dont know how to do it or if it is worth dooing,thanks all again,Kieron

 

[pampas]

The Petter oil switch has 2 terminals. (1) for the oil light (2.) for the oil side. Bit pricey if I remember so many folks did what you have to overcome the faulty switch, The only failure of this system is that one can start the engine and forget to fire up the alternator,
I have had to do this with a 60 Amp alt because it excites when the starter engages and the engine fails to pick up to idle revs.

 

[VicS]

The Petter oil switch has 2 terminals. (1) for the oil light (2.) for the oil side. Bit pricey if I remember so many folks did what you have to overcome the faulty switch, The only failure of this system is that one can start the engine and forget to fire up the alternator,
I have had to do this with a 60 Amp alt because it excites when the starter engages and the engine fails to pick up to idle revs.

The same could be achieved using the standard oil pressure switch and a relay.