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Harry.O

Member Since: 25 Jul 2014
Location: Warwickshire
Posts: 704

Radio Interference with Headlights on Full Beam

Last week I disconnected the battery do do some welding which triggered the alarm and BBUS as expected. Since then whenever I put the headlights on full beam (and LED lightbar triggered by full beam), there is significant levels of interference from the radio which has never happened before, dipping the lights and the signal returns to normal.

Disconnecting the battery has reset the settings on the head unit but I'm not aware of any settings that would have improved the radio signal itself beforehand. The FM channels are the same frequencies as before and my journey to and from work has remained the same route so it shouldn't be a radio coverage issue.

Anyone have any bright ideas? It's a 2005 TD5.

Thanks, Harry 2005 Td5 110 Hardtop
1989 300Tdi 90 Soft top
1992 200Tdi 90 Truck cab with Land Cruiser axles

28th Nov 2019 10:23am

sako243

Member Since: 08 Jul 2014
Location: Wales
Posts: 1185

1994 Defender 110 300 Tdi CSW Alpine White

If I understand the problem - you're only getting the interference when you've got high-beam on?

I'm assuming that you still have filament headlights? If that's the case then the first thing I'd check is the light-bar. Disconnect it so that it doesn't come on and see if your problem still exists. If it's a cheap light bar then they've probably got utterly crap constant current drivers for the LEDs in them which got damaged by the welding.

Where was the welding being done? MIG or TIG (steel / ali)? Did you put the earth clamp close to the weld puddle? Ed
82 Hotspur Sandringham 6x6
95 Defender 110 300Tdi

28th Nov 2019 12:03pm

Harry.O

Member Since: 25 Jul 2014
Location: Warwickshire
Posts: 704

Thanks for the reply Sako243.

The interference is only on high beam, this also triggers an LED light bar via a relay. The headlights are JW Speaker LED units and the light-bar is a cheap version but they have both been on for over a year with no problems beforehand. I'll pull the light bar later and see if that makes any difference

The welding was to the towing assembly so quite high amp MIG to steel and the earth clamp was also attached to the assembly - circa 8 inches away. The battery leads were removed before we started, which caused the radio to reset to factory settings but I don't think that would have made a difference to anything else? 2005 Td5 110 Hardtop
1989 300Tdi 90 Soft top
1992 200Tdi 90 Truck cab with Land Cruiser axles

28th Nov 2019 1:03pm

sako243

Member Since: 08 Jul 2014
Location: Wales
Posts: 1185

Try the light bar first, then perhaps the headlights since they're easy to disconnect.

Failing that I'd suggest swapping out the head unit if possible as that may have also been damaged. Afraid it's just a game of narrowing down the problem.

Another (remote) possibility might be the alternator since when you turn on the high beam it might wind up how much its outputting. Ed
82 Hotspur Sandringham 6x6
95 Defender 110 300Tdi

28th Nov 2019 1:06pm

Shax

Member Since: 05 Oct 2010
Location: London
Posts: 391

2010 Defender 90 Puma 2.4 XS CSW Stornoway Grey

A common mode choke in the feed to the light bar will help cut some of the interference.. It works a bit like the suppressor capacitor you put on a petrol distributor... ... ,-------,
.. I [__][_]|__
.. I __ |"_|"__|
.. "(o)====(o)"
^^_-^-_^-^_^^^^^--^^^^
PAUL
G7ALW 14.200 USB
26FB458 / 27.275 SSB

4th Dec 2019 12:35am

captain slow

Member Since: 22 Jun 2011
Location: Herts
Posts: 350

2014 Defender 110 Puma 2.2 CSW Corris Grey

I had a similar problem. Gary @ audiofile (who fixed it) put it down to interference from the LEDs. have a chat with him - he knows his stuff.

https://www.audiofile-incar.co.uk/ he's very good with Defenders 2.2 Tdci 110 XS CSW Corris Grey
Prince Harry's D3 (gone but not forgotten)
300 Tdi 110 CSW (gone but not forgotten)

4th Dec 2019 3:01pm

Harry.O

Member Since: 25 Jul 2014
Location: Warwickshire
Posts: 704

Thank you for all the replies so far

unplugging the light bar saw the radio signal return with the headlights still on high beam but I noticed this weekend that switching on the rear worklights causes the signal to go again so pretty sure it's the head unit playing up since the switch is located besides the head unit... seems like an excuse to upgrade to DAB!

Harry 2005 Td5 110 Hardtop
1989 300Tdi 90 Soft top
1992 200Tdi 90 Truck cab with Land Cruiser axles

9th Dec 2019 10:34am

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