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How sophisticated is SAAB's lamp sensing system? Posted by MI-Roger [Email] ![]() ![]() |
I have a problem with the right tail light not illuminating on my 9-5. It first appeared about 18 months ago when I replaced all lamps in both rear cluster, then miraculously resolved itself within a week. Not really, but the lamp worked.
The problem reappeared again after manipulating the wiring harness to the right rear lamp cluster to verify wire colors to connect my trailer harness. I 'assumed' there was an issue with a bad crimp in the lamp board wiring harness connector body (which cannot be repaired) or a break in the Pink wire near the board/connector that provides the tail light power to the right rear.
My plan was to jumper around the break by splicing into the wire and placing a screw terminal on the lamp board conductor bar going to the lamp. I was trouble shooting this morning prior to installing the jumper by exposing a short section of the pink wire in the spare tire well, slitting its insulation, and placing my 12V test light probe on the bare conductors to validate power is there.
Naturally, by the time I turn on the headlights, wait for the SID alarm message, clear the message, run around the car to the trunk area, and insert my test light in the slit, there is no power!
Two possibilities jumped to mind:
1) the break is elsewhere in the trunk area. or
2) the lamp sensing circuity with Orange Relay is sophisticated enough to interrupt power to what the car sees as a non-function lamp.
I swapped Orange Relays with my Viggen when this problem occurred earlier with no change in error, so I am 90% certain it is not an Orange Relay issue.
Guess I will drag my wife out to the drive way to turn on the lamp switch while my probe is inserted. Maybe I will see a flash of its light. After testing the tester on a Brake lamp signal to verify the tester is working.
_______________________________________ Saabs owned: 2008 9-5 Aero Sedan, sold at 227K miles 2006 9-3SC 2.0T - Wife's daily driver 2000 Viggen Convertible - Sold May, 2022 1964 Quantum IV Formula Car - Retirement project 2000 9-5lpt Sedan, sold at 318K miles
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