Main Beam Problem

[Guest ali2992]

Basically when I flash/turn main beams with sidelights on, the relay buzzes. This only happens when sidelights/dipped are on, otherwise they flash normally, is this a dodgy earth problem? Or feedback through the loom or something?

[WallerZ]

I have a relay that buzzes when my foglight comes on. The car is loud enough that I don't hear it when running so I left it. Plus the fog light never gets used as i'm never driving it in fog....now at least lol.

 

When I looked into it, I think i read that it was faulty....although as I write....I might be thinking of a diode...as I got 2 and one didnt buzz but one did.....I should think before I type...

[Guest ali2992]

I could cope with the buzzing if main beam actually came on when it buzzed, but it doesn't, I should add that when it buzzes, my voltmeter starts dropping and illumination on gauges etc dims

[Guest 2b cruising]

Have you tried a new relay yet?

[Guest ali2992]

I'm not convinced it is a relay problem as it works fine without sidelights/dipped on, if it was the relay it wouldn't work at all would it?

[Longboarder]

Relays usually buzz (if it's a rapid on/off switching buzz) when the effect of switching the relay on causes a voltage drop sufficient to stop activating the relay which then switches off again which restores the voltage which switches the relay on again which causes the relay to switch off and so it rapidly cycles creating a rapid switching buzz. This suggests a short in the circuit from the relay to one of the main beam filaments or a barely charged battery.

Are these circuits fused correctly?

Is the battery fully charged?

 

Nigel

 

ps missed the last post while typing. So is the battery fully charged?

Edited June 3, 2015 by Longboarder

[nigelt]

Sounds like you may have something wired wrongly to the relays for the side/dipped headlights. In other words when the relay for the side/dip is on it is also connecting the main beams circuit to ground, so that when you then try turning on the main beams the live feed is feeding to ground through the side/dip relay. this would be why the volts drop and then causes the chatter. A quick test (if you can) would be to disconnect the relay for the side/dip beams. Then turn them on from the stalk, as if they were connected and try the main beams again. Hope that makes some sense. However, as Nigel(Longboarder) says they should be fused and so this should blow.

 

Nige

[Guest ali2992]

Ok, I think I'm getting somewhere. I've managed to stop the buzzing. Initially the main beam relay earth was connected to the earth terminal of the dipped beam relay. I gave it a separate earth and the buzzing stopped. However, another problem arose. The gauges light up when sidelights are on, when they are lit up, and i then flash/switch main beam on, all the auxilliary gauges (they have separate switched live to rev/speedo) lose power (complete power, not illumination), turn main beam off and they come back on again. The loom connector for the gauges has 2 switched lives and 2 earths (i assume it was so you could spread the connections out, so I have speedo/rev using one of the switched lives and earths, and other gauges use the other two. I measured the voltage across the wire for aux gauge switched live and earth, and as soon as main beam comes on it drops to 0.

 

I also measured the voltage across the aux gauge earth connection, and chassis earth, now i'm relatively new to circuits etc but isn't the voltage across an earth wire going to be 0? Either way, the aux gauge earth wire would read 12v across it ONLY when main beam was turned on with dipped beam on. (Which leads me to believe its a dipped beam issue.) Strangely, the warning light panel (has a separate connector) loses an earth connection when main beam is turned on, as the main beam warning light wont show, indicator warning lights go off etc yet battery light and handbrake lights (using switched earth) remain on.

 

Finally, I tested the fog light, and blew either the main beam or dipped beam fuse (for some reason the 2 fuses have the exact same coloured wires coming off them.)

I have a few questions that might sound a bit silly but bear with me I'm learning as I go, the lost earth connection on the warning light panel and the voltage seen across aux gauge earth, is that caused by the current flowing the wrong way? I.e something short circuiting?

 

I have at most 2 earth points for the dash loom (gauges, ecu, warning lights etc), is that a problem?

 

Is there any tricks/methods to narrow down the source of this?

 

Sorry for the wall of text!

[Guest ali2992]

Also worth noting, the original mx5 that the stalk assembly came off used a switched earth system for controlling lights, the loom used a switched live system of relays. I took the earth connection used by the stalks as their switch point, and instead used it as switched live. I had to add in an extra relay to account for the 2 methods of switching main beam on (I wanted to be able to flash whenever I wanted, but be able to turn main beams on only if dipped were on) - the new relay was activated by dipped beam being on, and sent power to main beam relay (flash goes straight to main beam relay) - I used diodes to prevent anything going back the wrong way, it worked, but could this have introduced any issues? Its worth noting, the buzzing relay existed before I added in the extra relay

[nigelt]

This might help you if it is a MX5 stalk. It would appear that a great deal of the switching is done from the stalk and only one relay for headlights and main beam. Cluster lights are driven from the LG (Light Green wire) via a second relay. So your wiring maybe shorting out through the stalk.

 

Nige

[Guest ali2992]

Thanks, I've narrowed it down further today, I've got a significant voltage drop on several of the grounds (one from the aux gauge earth and one from warning light earth are the main ones) - does a voltage drop on the ground side mean that its an earth problem or a problem with the component that shares that earth? Particularly because there's a smaller (1v, still substantial, drop when sidelights turned on, then a full 12v drop when main beam on) Could it still be the stalk? I'm wondering if its shorting because I've changed how the stalk controls the switching (going to switched live rather than switched earth)

[Guest ali2992]

OK, I think I've fixed it. You'll laugh. It was one of the earth connectors. Cut it out, put a new one, miraculously everything works! Now I need to put the car back together as I took most of it apart trying to trace it...

[Guest Ian & Carole]

The law of sod strikes again. :ph34r: