Fitting a new circuit into the fuse box

[donkmeister]

I am planning to fit a few accessories to my Vectra that will need new circuits adding in. Keen to keep an OEM appearance, I don't want to add in a new fuse box or "piggyback" any existing fuses.

From reading on here, it appears the fuseboxes on these cars aren't a simple passive device with a couple of 12V rails inside, and need to be Tech 2'd when various things are added. Is this true if I want to add in, say, a 30A fuse and a relay into the underbonnet fuse box to power an airhorn compressor?

[mrk]

AIR HORN leave it out m8

[donkmeister]

Not a Colonel Bogie horn! The standard horns in a Vectra are a tad... limp. So this is a set of truck horns, albeit will be fitted under bonnet rather than on the roof!

[chrisvectra]

Vectra horns ain't usually limp you sure both the horn units are working or do u just wanna scare the bejesus out if people lol

[donkmeister]

Well, there's two times you want to use a horn:
1) To politely signal to someone who hasn't seen you ("dear boy, would you mind awfully terminating your reverse manoeuvre as you are about to back into me")
2) To assertively signal to someone who isn't paying attention that they're on a collision course with you and no matter how hard you are braking they still need to get out of the way.

Number 1 is served admirably by the parper on the Vectra, however when someone decided to change lanes on a motorway whilst I was alongside, I found capacity for number 2 frankly lacking. I don't want to go full-on train horn - whilst fun, that could just cause people to get scared and crash anyway. A truck horn is designed for use on the road, so a truck horn it will be.

So, I have bought some decent airhorns, complete with compressor. This requires a 30A fuse to power it, and as I will be activating it with a relay (and a switch in-car so I can deactivate the airhorn at will), I will also install a 30A relay.

I have installed amps to cars before, so have installed additional fuseholders, battery terminals and the like but it's always looked Heath Robinson in my eyes. However, I have never dismantled my fuse box before so wasn't sure what would greet me when I did, and if I would need someone with a Tech 2 to activate the spare ways in the fuse box.

So, anyone?

[keith1983]

When you say you will deactivate it at will do you mean you will turn it off and hope noone asks about it come mot time? It would be interesting to see what an mot station made of these horns. Or do you mean you will have to activate it on the road before using it? In which case that would be a bit pointless as you use such things in an instant and in my eyes at least it would be ineffective if there was the delay of switching it on in the first place?

[donkmeister]

Town and Country, I believe it's called! Couldn't find anything in the MOT guide that would forbid an air horn (musical horns are out, of course!), but say I am driving into the sort of situation where you may need to give a gentle parp to someone (festival car park field, supermarket car park etc), I can switch out the air horn. Out here you sometimes need to be able to toot an animal out of the way gently, again an air horn wouldn't be a great idea as it would spook it.

Right, so we've established the motive and means of use of air horns. Can you advise on the fuse box query? Please?

[donkmeister]

Right, so on closer inspection the spare ways in my fusebox do not have metal terminals within them. I will need to get hold of some additional terminals to install, and take it from there.

Either I will need to run dedicated wires through the back of the fusebox (easiest option) or find spare ways on the bus-type connectors into the back of the fusebox and insert pins The latter is the more difficult option, if nothing else because I need a 30A terminal and spare ones may be hard to come by as it's got most of the toys fitted already. We'll see!

Of course the auxiliary fusebox option would be easiest of all but I'm avoiding that if possible.

[nokiaman1978]

think the Vectra horns are loud enough as standard.

[Handyandy-UK]

There's plenty of scope for horn upgrades just staying within OE items as the setup varies with trim levels :

1	13109056	6228138	HORN,ASSY.,335HZ. (NLS.- USE 13173094 62 28 027)	1
1	13173094	6228027	HORN,ASSY.,335HZ.	1
2	13210448	6228033	HORN,ASSY.,370HZ. (NOT USED WHEN FRONT FOG LAMPS FITTED)	1
3	13105269	6228135	HORN,DUAL,400 HZ.,RH	1
3	13105270	6228136	HORN,DUAL,500 HZ.,LH	1
4	13183104	6228143	HORN,DUAL,400 HZ.,RH (EXCEPT CHINA)	1
4	13253736	6228035	HORN,DUAL,400 HZ.,RH (FOR CHINA)	1
4	13183105	6228144	HORN,DUAL,400 HZ.,LH (EXCEPT CHINA)	1
4	13253737	6228036	HORN,DUAL,400 HZ.,LH (FOR CHINA)