Strange Electrical Glitches

[nico506]

Hi All,
Thanks to everyone who helped me in sorting my eletrical problems on the headlight wring on my S3 SE Elan -which has S2 wiring arrangement ( relating to the headlamp and dip relays located under the dash and engine bay respectively).

Having completed the wiring and fitted the above relays I now have further funny faults:

When I pull up the LHS headlamp the relay and flasher unit in the engine bay emit a loud buzzing noise and the LHS indicators glow faintly when this happens.

Also when I power up the electrics i.e connect the battery- the ign light comes on and the sidelights come on (faintly).

I must have a short somehwere and ask if the relays are meant to be grounded to earth in any way and before I had this fault - the headlamps lit up via the microswitches when pulled up and no buzzing.

Any ideas?- should the earth circuits be separated from the headlight, sidlelights and indicator circuits ?- I have all earths connected to a solid clean point.

Any tips or ideas appreciated.

Thanks

[paddy]

I would really suspect an earth connection.

When you pull up the headlamp unit, it activates the microswitch that is for the "headlamps up and flashing to get people to get out of your way" function. The microswitch grounds the relay, which then makes the light come on. I can't remember if the flasher unit is in the circuit for the relay coil, or in the main circuit for the lamp, but either way, it is meant to flash.

It sounds to me like the ground wire for the headlamp is connected to the ground wire for the indicator light, but neither is well connected to the actual ground of the car. Thus the current tries to go through the headlamp, then goes through the front indicator (in the reverse direction, so to speak), then through the rear LHS indicator (in the right direction), and finally to ground through the (good) ground connection for the rear indicator light. Thus all three lamps get only a fraction of the full 12v, and light dimly. In all of that, there is insufficient to activate the relay, or the flasher misbehaves, or something and the relay/flasher just buzz.

So I would double-check that the ground wires are all well grounded.

As a further diagnostic step, try removing the bulb from the front LHS indicator. You ought to find that everything stops completely (ie no buzzing, no lights). (Alternatively, it might do the same thing, but via the sidelight -> sidelight circuit).

Paddy

[handi_andi]

This regularly happens on my plus 2, solution is to pull the ground leads off the relays. All relays reset, alternatively and probably quicker pull a lead off the battery, and then reconnect and it goes away. My experience is that modern relays just aren't what they used to be and have a habit of sticking, particularly if not used for some time. Once all the relays in the headlight circuit have been activated a few times then I don't get the problem re-occuring until such time as I leave the car laid up for a while.

Andrew

[oldelanman]

Is your battery fully charged ? Might be nothing to do with your problem but I had a similar situation when reconnecting and testing my electrics. I had no battery so was using an old battery charger as a 12 volt supply to test each circuit. It worked fine until I got to the headlamps and there I had the buzzing relays and headlamps not working. Eventually I twigged that the charger could only supply 5 amps so it would operate the relays with no load on them but with the headlamps connected there was not enough power so the relays were cutting in and out. Bought a new battery and everything worked fine.
regards,