right low beam headlight shuts off immediately

2007 VOLVO XC70
114,000 MILES • 2.4L • 5 CYL • TURBO • AWD • AUTOMATIC
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MIKWIK
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I turn the key and both left and right DRL's come on, but the right dip light shuts off immediately, even before car starts. It stays off when I switch from DRL's to Headlights. Bulb works, fuse is good, and all other bulbs in headlight assembly work as they should. If I disconnect the main wire harness to the headlight assembly then start the car and wait a few seconds before reconnecting it, the dip light will stay on. Light functioned properly as I was shutting off the car and restarting it several times. When I tried again two hours later the same problem.
Dec 8, 2016 at 11:46 AM
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STRAILER
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Hey MIKWIK

Thoses cars have a main headlight controller that goes out, kind of like an amplifier which can't handle the load.

Here are some diagrams to help you understand.




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Dec 12, 2016 at 12:28 PM
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MIKWIK
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Thanks for the diagrams. It looks like a CEM issue. I'll check for continuity from CEM harness to headlight harness. I will check for a steady flow of power at the CEM B4 pin when the key is turned on.
Dec 13, 2016 at 5:27 PM
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STRAILER
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Please let us know what you find so it will help others.

Best, Ken
Dec 16, 2016 at 5:01 PM
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MIKWIK
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Problem solved. Bad CEM. Pin B4, blue/yellow wire(low beam power supply), connection to board was broken/cracked/loose???. When powered up, the pin would "shut down" in a milli-sec with or without a bulb in the socket. Wire harness and all connectors from CEM to bulb socket always had conntinuity. Replaced CEM with "better than new" reman unit from Xemodex. Expensive but all other "prone to fail" issues with the unit have been addressed so I shouldn't have any other electrical problems associated with the CEM. Thanks again Ken
Dec 18, 2016 at 2:18 PM
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STRAILER
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Nice work MIKWIK, thanks for getting back to us, please use 2Carpros anytime, we are here to help.

Happy Holidays!
Dec 18, 2016 at 5:44 PM