X70 Led Swap: The Thread


T5power
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  • 3 months later...
On 8/4/2013 at 7:39 PM, hasbeen179 said:

I read through - couldn't find an answer -

 

I've successfully replaced almost all the interior lights with leds.

 

My one issue is the courtesy lights over the rear driver's and passenger side doors.

 

I've used the "right" bulb, rotated them around re: polarity, even grabbed a couple new assemblies on my last trip to the u-pull. Tried different bulbs of the same type, just in case.

 

Nothing, except the stock incandescent, works. Can someone dumb this down for me? Thanks in advance!

Yeah yeah, old thread or whatever. I've started swapping over some of the dome/courtesy lights in my 1998 V70R over to LED and I got stuck on these lights over the rear seats too. Had me stumped for a good hour. LED bulbs worked fine when hooked directly to power, and the regular bulbs worked fine in the sockets.. there was no reason that I could think of why it wouldn't work.. Then I figured it out I think. Volvo uses a single power wire going to the light fixture (single wire plug) and the switch picks out which ground makes contact to either work with the dome lights or on constantly. They actually have the light socket wired backwards. The type of bulb used here would usually get power from the center stud at the bottom of the bulb and the outer casing (the pins) would be the ground. I'm this application Volvo uses the outer casing of the building as the positive and the center stud as the negative. This would have no effect on a regular bulb, but the LED will only work on a certain polarity. A simple tab bulb like a 194 would be easy to flip over and it would work, not the case as these would work the same no matter which way they are installed. So now the mystery is where to source an LED like this that is setup for reverse polarity. Has anyone found a solution?

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5 hours ago, tuner4life said:

Yeah yeah, old thread or whatever. I've started swapping over some of the dome/courtesy lights in my 1998 V70R over to LED and I got stuck on these lights over the rear seats too. Had me stumped for a good hour. LED bulbs worked fine when hooked directly to power, and the regular bulbs worked fine in the sockets.. there was no reason that I could think of why it wouldn't work.. Then I figured it out I think. Volvo uses a single power wire going to the light fixture (single wire plug) and the switch picks out which ground makes contact to either work with the dome lights or on constantly. They actually have the light socket wired backwards. The type of bulb used here would usually get power from the center stud at the bottom of the bulb and the outer casing (the pins) would be the ground. I'm this application Volvo uses the outer casing of the building as the positive and the center stud as the negative. This would have no effect on a regular bulb, but the LED will only work on a certain polarity. A simple tab bulb like a 194 would be easy to flip over and it would work, not the case as these would work the same no matter which way they are installed. So now the mystery is where to source an LED like this that is setup for reverse polarity. Has anyone found a solution?

Having a hard time understanding what you're saying; can you post a schematic, either from the manual or hand-drawn?

Are you saying the bulb gets current applied in both directions, depending on the use-case?

 

Since you opened the topic..  :happy:

Is there a good LED replacement for the 9148906 bulb?

Edited by gdog
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I don't have a schematic or anything and I've been battling photobucket to find the pictures that I took, but the basic summary is that the bulbs used in the rear courtesy lights (over the doors) on my 1998 V70R use the style of bulb shown in the picture here. I've labeled the + and - contacts for every application that I've ever seen. This is also the way that the LED replacements I have found are meant to be powered. Also to note, the front dome/map lights take this bulb also and are wired in the normal fashion because the LEDs work up there.  The light housings at the rear are switched. The bulb receives power through the outer casing and is grounded at the tip. The switch on the housing determines if the light is grounded at all times, or only when the door is open. So basically to find an LED that will work in this spot, we need to find one that is wired backwards of the normal.   

 

 

bulb 1.PNG

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I looked at the schematic and don't see any cases (unless I missed it) where the current might go in two different directions in the courtesy lamps.  If you pop out the light fixture, you should see a red (or red w/white tracer) wire supplying the 12V+ and black (or blue w/black tracer) wire supplying the ground.  Unfortunately the schematic I have doesn't have the lamp descriptions so I may be guessing in some of these cases.  They're all labeled 10/22, 10/24, 10/29, etc. on the schematic.

Is it possible somebody re-wired these particular sockets backwards?  Ck it with your VOM.

Edited by gdog
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