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Bluest



Member Since: 23 Apr 2016
Location: Lancashire
Posts: 4217

United Kingdom 2007 Defender 110 Puma 2.4 XS CSW Java Black
Electrical conundrum
I’ve had Mobile Centre cruise control installed for a long time now and it has always worked perfect until recently. The fault is related to some driving lights I’ve fitted so I must have cocked something up when I installed those.

This occurs when driving with cruise control on. The problem is that sometimes, when I switch to main beam with driving lights activated so they come on with main beam, the cruise control will cancel, needing me to re engage it. This happens the instant I activate the main beam, and I re engage and drive with cruise control and main beam on. I’m thinking activating the driving lights is causing some sort of momentary drop or loss in power to the cruise control, but don’t see how.

The problem doesn’t occur on every occasion, only about 25% of the times I put main beam/driving lights on.

Doesn’t happen if using main beam without driving lights.

When the fault occurs, the cruise control unit emits two short beeps.

Cruise control is wired as per Mobile Centre’s instructions

Headlight/Mainbeam is wired through a Landreiziger Loom, powered straight off alternator.

Driving lights are wired through the dash switch so they are either off, or on with main beam, as per that pdf diagram that’s is floating about on this forum. Driving light power is taken straight off the alternator stud. Two Driving lights are 130w Halogen each. 2007 110 TDCi Station Wagon XS
Post #676375 6th Jan 2018 3:04pm
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pannawonica



Member Since: 21 Nov 2010
Location: Clackline Western Australia
Posts: 568

Australia 
Unusual electrical issues make me suspicious of a bad earth somewhere! Thumbs Up
Post #676527 7th Jan 2018 3:46am
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Screbble



Member Since: 26 Apr 2015
Location: Lancashire
Posts: 2108

United Kingdom 2004 Defender 90 Td5 XS CSW Zambezi Silver
I haven't got cruise control so can only offer a general comment.

I agree that it is probably likely to be a high resistance or faulty earth connection somewhere.

It might be worth taking a look (if possible) at the earth connections you have made for both installations. Are any of them common (if you pardon the pun)?

I know the wiring diagram you refer to so I'd have a closer look around the relay you've installed for the driving lamps as I recall the dash switch makes/breaks the earth to the coil.

With the two circuits being entirely separate, and the feed for the lights coming straight from the alternator, I can't think of anything else obvious.

Sometimes it's worth getting someone rise to look over the installation as they will see things you don't if you know what I mean. Easier said than done I know.

Hope you get it sorted Thumbs Up
Post #676547 7th Jan 2018 9:03am
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 17450

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
It may be a noise or inductance related 'feature'.

Ever since I rewired my headlights via relays I get a half-powered flicker from both indicator tell-tales on the Ipac and the trailer indicator tell-tale whenever I go from main to dip. I suspect that somewhere there's a 'switching transient' causing this, but I've never been concerned enough to do anything about it.

It could be a similar phenomenon witb your CC.
Post #676548 7th Jan 2018 9:09am
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Bluest



Member Since: 23 Apr 2016
Location: Lancashire
Posts: 4217

United Kingdom 2007 Defender 110 Puma 2.4 XS CSW Java Black
Panawonica, Screbble - I will check the earths. The spots are earthed to a bolt on the ac compressor, but I can’t recall where the earth for the cruise control went to. It’s possible the earth for that is shared with the driving light dash switch illumination/tell tale, which coincidentally failed recently.... Question

Black wolf. I too get the momentary flash of the indicator tell tales when coming off high beam. It irritates me but am not smart enough to understand the cause! 2007 110 TDCi Station Wagon XS
Post #676552 7th Jan 2018 9:37am
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rallysteve



Member Since: 10 Feb 2014
Location: Cumbria
Posts: 2237

United Kingdom 2002 Defender 110 Td5 DCPU Keswick Green
Both,
Using relays with a resistor built in (believe the yellow LR ones have this) should help with this. It is probably caused by back emf when the relay coil de energises. You could also use a relay with a diode built in but you have to be careful that the relay coil is wired correctly or you will have a short circuit. I believe diode relays are wired differently to the DIN standard 85/86 terminal designations.

Try swapping your headlight relays (assuming you have used 4 pin ones) for a couple of yellow ones in the fuse box and see if it goes away.


Steve 02' 110 TD5 Double Cab Rebuild Thread
Post #676559 7th Jan 2018 10:53am
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MadTom



Member Since: 10 Sep 2013
Location: Olomouc
Posts: 625

Czech Republic 1999 Defender 130 Td5 HCPU Baltic Blue
Or you can add diodes to the current relay coils. For the diode something like 1N5408 is more than enough, and cost nearly nothing. Diodes must be placed just next to the relay, with short wires connecting them. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo Smile
Post #676574 7th Jan 2018 12:09pm
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 17450

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
rallysteve wrote:
Both,
Using relays with a resistor built in (believe the yellow LR ones have this) should help with this. It is probably caused by back emf when the relay coil de energises. You could also use a relay with a diode built in but you have to be careful that the relay coil is wired correctly or you will have a short circuit. I believe diode relays are wired differently to the DIN standard 85/86 terminal designations.

Try swapping your headlight relays (assuming you have used 4 pin ones) for a couple of yellow ones in the fuse box and see if it goes away.


Steve


Steve, many thanks. I replaced the standard relays I had for dip and main with genuine yellow LR ones at the weekend and the flicker phenomenon has gone. It doesn't matter if the relays used are the Tyco or the Siemens type (both yellow and both genuine - I tried both types as I have a number of each), the fact that they have the on-board resistor appears to stop the flicker.

Another interesting feature which I hadn't noticed until fiddling around with relays at the weekend is that with the old, non-resistor-fitted relays, the flicker only happened if the engine was actually running. If the ignition was on but the engine wasn't running there was no flicker. Although I still don't quite understand the exact mechanism by which the ficker was occurring, the better relays have cured it.
Post #678650 15th Jan 2018 11:21am
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rallysteve



Member Since: 10 Feb 2014
Location: Cumbria
Posts: 2237

United Kingdom 2002 Defender 110 Td5 DCPU Keswick Green
Excellent Thumbs Up

Always nice when a theory works, cheers for confirming.

Steve 02' 110 TD5 Double Cab Rebuild Thread
Post #678652 15th Jan 2018 11:28am
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blackwolf



Member Since: 03 Nov 2009
Location: South West England
Posts: 17450

United Kingdom 2007 Defender 110 Puma 2.4 DCPU Stornoway Grey
Hmm, it seems I posted too soon. Big Cry

It was daylight when I swapped the relays around, and it was dark when I drove home from work. There is actually still a flicker from the three indictor warning lights after all, I just couldn't see it in daylight. It may be dimmer than before (it is hard to tell) but it's still there.

It is not a problem, but it is a puzzle.
Post #678742 15th Jan 2018 6:50pm
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