Allegro Club International

[Colin T]

The wiring diagrams for S3 cars show a 'front foglamp fuse'. This is connected to the headlight position of the main lighting switch and to the rear foglamp switch, and can also be connected to the front foglamp circuit.

There appear to be two options as to how to connect this fuse:

Option 1 - Directly from the headlight position of the main lighting switch to the rear foglamp switch.

Option 2 - Connected as a 'side-branch' off from the wire coming away from the front foglamp switch (which continues on its own to the front foglamp relay) and then continuing to the rear foglamp switch.

These options can be chosen by swapping the blue wire with male connector near the wiper motor from the female connector with one blue wire (option one) to the female connector with two blue wires (option 2). The front and rear foglamps both work with either option.

Is Option 2 the correct option to use when front foglamps are fitted? It appears so to me as it seems to add the fuse to the circuit, but as some sort of by-pass option from the main power supply to the front fogs. (I don't really know much about electrical circuits).

Can anybody explain exactly how this fuse works in the circuit?
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Colin T]

OK, this is more complicated than I first thought.

With Option 1, the font and rear foglamps operate independently. The fronts can come on with the sidelamps or headlamps, the rears only come on with the headlamps.

With Option 2, the front foglamps will work independently, but the rear foglamps will only work when the front foglamps are on. Both front and rear foglamps can come on with the sidelamps or headlamps.

I just don't understand any of this............
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!

[Richard Howe]

Option 2 isn't completely insane; it's the default in my Merc. I think the reasoning is that your need to see where you're going kicks in before your concern for those coming up behind you I think it makes the most sense, just be sure your MoT tester knows that the rears won't work without the fronts, or better still put them both through a single 3-position switch - this is how the Merc works, you have to use the same switch in 2 positions for either Front or Front & Rear fogs.
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...that's why Allegro will look as good 5 years from now as it does today.

[Colin T]

OK, I now understand how the wiring works for the foglamps.

What I have described above is correct in terms of the operation of Option 1 and Option 2.

My handbook, which appears to be the first edition of the Allegro 3 handbook, states that the rear foglamps work with either the sidelamps or headlamps. This is incorrect as seen in operation and by tracing the wiring. The error in the handbook has been corrected in a later edition, which was used for Feb '81 facelift cars onwards. The later handbook states that "The rear fog-guard lights only work when the headlights or front fog lights are switched on." This is correct, in terms of Option 1 and Option 2 above, but is slightly unclear as you could reasonably assume from what is in that handbook that you could put the headlights on and then the rear foglamp will work - but it won't if you have Option 2 selected!

Also, looking at the wiring makes me come to the conclusion that the item marked as "No. 45 - front foglamp fuse" is in fact a fuse for the rear foglamps! If the wiring is connected such that neither Option 1 or Option 2 is selected, then I think the front foglamps will work fine and the rear will not function as power to the rear foglamps passes through this fuse from either the headlight position of the main lighting switch or from the front foglamp circuit (I would check this but I've just found that my car's battery is flat, having stood since Saturday night!).
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Hell has frozen over...... the car formally known as 'Heap' is back on the road!