Electrics

[caterhamnut]

Couple of things:

Horn - does not work - can hear a 'click' of a relay but no BBLLAAAGH of a horn. Any ideas?

 

Also, anyone got a 'map' for my fuse box. It is not the same as the one illustrated in the users 'manual' - it is rectangular, columns of fuses about 4x5 (approx - sorry, not by the car right now) and I really would like to be able to identify each fuse without going through a process of elimination each time. Car is '96 1.6SS k.

cheers

 

😬41,000 miles in 21 months!

angus@tinyworld.co.uk

Caterham pics

here

[Sheds Moderator]

Lost the post, I think. Here goes again. Sorry if this is granny and eggs. I imagine your horn is permanently connected to earth via the body. If not it will have 2 leads, one to earth and one to +ve.

 

1. Check the earth connection with a multimeter set to ohms. Should be c. zero. If it isn't then you have the electrician's favourite the Bad Earth, which ought to be a 70s heavy metal band. Then check the resistance of the horn between pos feed and earth. Should be a few ohms, or tens of.

 

2. With the tester set to volts, check for a pos feed with the horn button down. If there is an earth and a supply, dead horn. If not, trace the wire back to the source (you talk about a relay which is unusual, but there you go) and check there. Carry on in an orderly fashion, it is after all a simple circuit, the relay excepted.

 

Bet it's corrosion related.

[Chris W]

Angus

 

I agree with everything that Battered suggested except the relay bit. It's not actually unusual to have a horn relay.... it would be unusual not to have one. If you do get +12v on the meter at the horn positive itself when you push the horn button, the relay is working fine.

 

If not, check that the horn relay (which should be with the fuses) is well pushed into its socket (basically push all the relays well home cos you won't know which one is the horn relay!). Although you can hear its clicking, that doesn't mean all the terminals are necessarily connecting.

 

Otherwise it has to be a poor earth connection as Battered suggested or the horn itself is kaput.

 

good luck

 

Chris

 

1.8K SV 140hp see it here

[prs]

Have just fitted a set of air horns and had some fun as I didn't know there was already a relay fitted!!! but that's another story.........

Angus the horn relay is the TOP relay in the fuse box, if it clicks when you press the horn then it's working (if you put your finger on it you can feel the click). If the horns are still not working then it must be an earthing problem.

 

Phil AV02NJO 1.6SS

[Peter T]

It's quite possible that the diaphram has siezed up through lack of use! There is a small nut for adjusting the pitch or tone of the horn on the top of the uint, if you undo it and move it slightly then it might do the trick!. If all else fails then substitute the horn for a uinit that is known to work.

 

Anyone for Tennis?

[Chris W]

Just a point... got to respectfully disagree with Phil, hope this doesn't sound too pedantic.

 

The fact that the relay clicks doesn't necessarily mean that its working correctly. The click means that the relay coil is receiving current and the switch contacts are closing (that's the click you here). However, a switch contact could have broken from its terminal inside or a terminal may be corroded and thus not making proper contact in the circuit.

 

So while a click is a very encouraging sign, and probably means the relay is working, it is not of itself absolute evidence. This avoids those situations where someone says 'I've checked everything and still can't find the fault".

 

The relays used for the horn, lights and indicators are all identical (certainly on recent models) so substitution is a very sound method for checking the relay. If you pull the relays out noting which goes where, look at the labels to double-check they are indeed identical and try a substitution. Still the biggest chance is that the fault lies with the horn itself or its earth.

 

Chris

 

1.8K SV 140hp see it here

 

Edited by - Chris W on 21 May 2003 12:26:04

[I.Mupferit]

Angus, I've got a spare relay in the garage which I can bring along tomorrow night if you want to try it.

 

Let me know if you want it.

 

Brent

 

[caterhamnut]

Thanks guys - i will have a fiddle later 😳

Only realise how much you need it when its broken and some idiot cuts you up etc!

 

I'll try the substitution method first - funnily enough, ithe horn has always been a bit dodgy, so i suspect a lose connection somewhere.

 

Thanks anyway Brent - the other elays are indeed the same, so no need to borrow one.

 

😬41,000 miles in 21 months!

angus@tinyworld.co.uk

Caterham pics

here

 

Edited by - angus&tessa on 21 May 2003 13:28:19

[I.Mupferit]

Doh! Yep of course they are, wasn't thinking. Anyhow if it does prove to be a dodgy relay, let me know and you can have my spare tomorrow.

 

Brent

 

[Pierre Gillet]

My fog light does not work. There is no positive at the lamp when I turn the switch on. The lamp and fuse are OK.

Could the switch be broken ? Car is 1997.

I have also noted that there is no positive on the two leads that come in and out of the switch through the "back plug". The switch is lighted though when I turn on the general lighting switch and there is a positive on the "lateral" plus lead.

 

Pierre

[Sheds Moderator]

This could be another relay job. The fog lamps only work when the lights are lit and this is generally controlled by a relay. The fact that you have no supply to the back of the switch other than the supply to light the switch itself indicates the switch is probably not at fault and the problem lies elsewhere. I suspect the relay, so give them all a wiggle. Swap them as required. I have no wiring diagram here but I suspect that's how they work.

 

Cats are prone to corrosion, something to do with getting wet both sides, and I know you use yours the year round, Pierre. 5 or 6 years is a good time to get corrosion related electrical faults...

 

From memory the general sequence of feed goes something like:

 

+battery, common +ve somewhere in the fusebox area, fuse, switched contacts of relay, dashboard switch, bulb holder, bulb, body, earth return via chassis. The relay is only activated by turning the main lights on.

 

I reserve the right to be wrong here, especially with regard to the precise sequence of fuse and relay and dash switch, but the principle is the same. You have already established no supply to the back of the switch so you are halfway there.

[Chris W]

Pierre

 

Standard wiring for the fog lamp(s) is from the dipped beam headlights (ie: standard wiring will turn OFF the foglight with main beam ON). There is no relay specifically controlling the foglight other than the fact that of course the headlights are worked through a relay. If the dipped beams are working, then the headlight relay is working.

 

If you have no volts at the back of the switch, then you have a disconnect somewhere between the foglight switch and the supply from the dipped beam. The foglight is connected to fuse 5 (check you have power there). However fuse 5 derives its power from fuse 9... check this is OK and that you have power at both sides of it.

 

Chris

 

1.8K SV 140hp see it here

[Pierre Gillet]

Battered, Chris

thank you for your analysis. Will try tomorrow both sides of fuse 5 and 9.

Cheers,

 

 

 

Pierre