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LED conversion - resistor location for brake lights and directionals

Help, Advice, Owners' Discussion and DIY Tutorials on Volvo's stylish, distinctive "P2" platform cars.

2001 - 2007 V70
2004 - 2007 V70 R
2001 - 2007 XC-70
2001 - 2009 S60
2003 - 2007 S60 R

user17600
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Year and Model: V70A, 04; XC70, 06
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user17600

LED conversion - resistor location for brake lights and directionals

Post by user17600 » Fri Feb 17, 2017 6:18 pm

All, for those that have performed a LED conversion (or thought about it) on a P2 V70 how did you identify the wires for the brake lights and directionals for installing a resistor to stop error messages on the DIM/cure the rapid flashing issues.

I did try modifying the shunt (as described here: viewtopic.php?t=51227), but was unsuccesful - when I completely sever that arm of the shunt I get no lights whatsoever, and without severing that arm (drilling a hole in that arm), I still get an error message (both even with a resistor soldered in place).

So I'm resigned to using resistors (I'm starting with 25W versions), but can't figure out which wire is for what in the harness, either looking at it in my car or on a wiring diagram. And I don't want to start poking around and damage anything.

So the question to convertee's: where did you place the resistors for the brake lights and directionals?

Thanks in advance.

Canadian Moose
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Canadian Moose

Re: LED conversion - resistor location for brake lights and directionals

Post by Canadian Moose » Fri Feb 17, 2017 8:14 pm

I did full LED conversion on my car.

I modified the shunts for brake lights and tail lights. I couldn't figure out a way to get the turn signals working by modifying the shunts so I had to use resistors. Resistors can be added anywhere in the circuit. You need 2 50 ohm resistors per side. I placed mine in the trunk cavity away from anything that could melt or catch on fire.

I highly suggest not using resistors for tail lights as they will get super hot.

Here is a video of my setup.



Here is a diagram showing how I wired my turn signal resistors.
turn signals.jpg

user17600
Posts: 28
Joined: Mon Jun 14, 2010 6:04 pm
Year and Model: V70A, 04; XC70, 06
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user17600

Re: LED conversion - resistor location for brake lights and directionals

Post by user17600 » Sat Feb 18, 2017 5:59 am

Thanks, Moose. You've actually done exactly what I'd like to do with my '04, including the headlamp conversion - I love the projectors and need to try to source the lenses rather than using my fluted ones.

I did try your shunt method, but as I said above, when I drill through the shunt and break that arm completely, I get no current at all for some reason, I even tried a variety of resistors without luck. Did you completely sever that second arm of the shunt (drill through and cut it in half) or did you leave a bit of the original metal, thus introducing a small path for voltage? Maybe I have a bad shunt - I'll go back and try another.

In terms of the big resistors, how far up did you wire them in? Did you tie them directly to ground or use the small black wire that feeds each lamp? I guess I was hoping to have them much lower like you do, but want to avoid any long runs of wire to support them. Maybe I'll trace back the green and green/white wiring and bridge it lower.

W/r/t the actual wires, what threw me is that that green wire voltage varies when the directional is on and is stable when the brakes are on. So I was completely fooled by which wire was which.

Thanks again.

Canadian Moose
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Year and Model: 2002 V70
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Canadian Moose

Re: LED conversion - resistor location for brake lights and directionals

Post by Canadian Moose » Sat Feb 18, 2017 6:24 am

I cut right through the shunt to sever the connection and then soldered a 10 ohm resistor in its place.

I actually replaced the wires that attached to the 50 ohm resistors with longer ones so I can hide them in the trunk. I attached to the black ground wires in the harness.

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