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Converting to LED bulbs

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

2001 - 2007 V70
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Canadian Moose
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Converting to LED bulbs

Post by Canadian Moose » Mon Nov 28, 2016 8:22 pm

I am in the process of converting my 2002 V70 to LED bulbs. I already have HID projector headlights so LED everything else was the next thing to upgrade. Tonight I swapped the brake lights, one set of the tail light bulbs and license plate lights to LEDs. Tail lights work fine, no issues. Brake lights however are displaying a warning message on the cluster about bulb being out. Looks like I will have to mess around with current sensing shunt or add load resistors. No biggie.

Just curious as to what I should expect when I swap front and rear turn signals to LEDs? Will they hyper flash or will I simply get a warning message? What controls the flashing? Is there a lightning control module or sorts like a on some Fords that has a built in flasher or is there just a flasher relay like older cars? Would someone have a wiring diagram for the turn signals so I could plan ahead?

s10lowrider1994
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Re: Converting to LED bulbs

Post by s10lowrider1994 » Mon Nov 28, 2016 11:38 pm

I had to use a load equalizer thing on my bike to make them work correctly. Didn't cost much and was easy to wire up, I imagine you'll need something similar to avoid the quick flashing and bulb out warnings.

Canadian Moose
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Re: Converting to LED bulbs

Post by Canadian Moose » Thu Dec 01, 2016 7:48 pm

I think I figured out how to disable the warnings by modding the shunts. Will post details when I swap all the lights to LED and verify they work.

Canadian Moose
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Re: Converting to LED bulbs

Post by Canadian Moose » Tue Dec 13, 2016 9:07 pm

After screwing around with this for the last week I came up with a solution. I tried using load resistors initially and and they got so hot within a minute of having the lights on that I just wasn't comfortable having them in the car because eventually they would start melting things or worse, start a fire. Plus using load resistors kinda defeats the power savings of LEDs.

The solution turned out to be quite simple. It involves modifying the shunts and replacing a resistor with one that has higher resistance thus fooling the REM into thinking the bulbs are still present. This is essentially what load resistors do except this is done at the REM rather than the bulbs themselves.

I got the idea from this site.
http://www.xenonvalot.com/xenonfixvolvo.html

I went to a junkyard and grabbed a bunch of shunts to mess around with. After inspecting the wiring diagrams I came to a conclusion that the shunt has a couple of resistors inside that are used by REM to sense when the bulb is out.

The resistance values listed on that site appear to be incorrect though. My measurements showed about 2.6 ohms between pins 2 and 3 as well as 1 and 2.

Here is a picture showing what a shunt looks like inside as well as a modified shunt.

Top left shows what a shunt looks like on the inside. I took a grinder to it and removed top layer of the plastic that exposed the guts. The metal traces that you see there actually act as resistors.

In order to modify it one of the metal traces needs to be broken and a new resistor soldered in its place. I ended up simple drilling a hole through the metal trace. Then using a box cutter I removed plastic covering the traces so I could solder a new resistor in its place.

I soldered a 10 ohm resistor in there to try. My theory is that once the resistance is above a certain value, the REM assumes that the bulb is not burned out.

So far I tried this on brake lights and tail lights and this eliminated the warning messages. Next I will be trying this on the turn signals.
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