Iva Fog Light Circuit Testing

[Guest 2b cruising]

Definately gauge adapter.

[sj-bradley]

Ok then. That's going to be my next project when I get back.

 

After I finish doing a batch of steering column covers in various colours ...

I'm also wondering if I can make a vacuum forming machine as I could then make them in seconds rather than hours

 

Simon.

[fry61]

Fuel gauge adaptor/corrector would be welcome.

The ballast lamp is not necessary if an OFF --ON --ON ( spring return for second ON ) is employed -- as per a wiper plus wiper& wash switch. The first On position is used to supply relay switch +12volt from tapping the feed to the dip switch & the spring return ON feeds =12volt to the relay coil which is then held closed by a link wire from load side of relay switch. If this wipe/wash switch is returned to OFF rear fog goes out as normal , if fog light is left on then switching off the ignition or the headlights will break relay coil feed & fog light will go out & not be illuminated on further ignition or head lights being switched on as the spring return needs to be closed to power the fog light once more.

[fry61]

Good idea, but that ballast lamp could fail leaving you scratching your head as to why it's no longer working.

 

 

The ballast lamp is tested ( illuminated ) every time the rear fog is switched off normally --momentary 12 volt is fed to earth side of relay thus coil de-energised ( =12v each side ) plus full 12v across ballast lamp.

[sj-bradley]

So, does that mean if the ballast lamp fails that the Fog light then turns on? Also, are you momentarily shorting 12 volts to ground?

 

Curious,

Simon.

[fry61]

The ballast lamp is there to provide a low resistance path to earth for the coil & when +12v is applied to both sides of coil the ballast lights instead of there being a short circuit, ( as said +12v each side of coil & it de-energises ) if the ballast lamp fails that would be immediately checkable by momentary switch UP position. Should there be failure of this lamp fog cannot be turned on as there is now no path to earth for the relay coil.

 

Think my second circuit with the wiper/ momentary wash switch is better, no ballast lamp required & as before just the one relay fed from link wire between headlight switch & dip switch.

 

I used a lamp for an earth path as it has a very low resistance when cold & back EMF from the coil will reduce coil current once energised thus further reducing amps & lamp will not illuminate.

There is probably a better electronic type resistor that will serve but auto bulbs are very robust -- how often does a 5watt lamp fail on any of our cars?