05 Lincoln LS electrical gremlins

BrunoWilimek · February 26, 2009

I've got this 05 Lincoln LS with about 56,000km on it that has 2 unrelated(likely) intermittent problems that I have not been able to reproduce. First off, no DTC's that seem to relate to the problems. First problem, the turn signals make a "horrendous noise" in the words of the customer. It has done this several times for the female driver as well as her husband and son. She described it to me so I can't really say exactly what it sounded like(if you know what I mean). Posted Image Second problem is the heated seat switches that intermittently have the three red lights blink in sequence for each seat. Sort of like the lights on the front of the Knight rider's old Trans Am from the original TV show.(if I understood the description properly) The heated seats work fine the rest of the time, but she says when the lights are doing their funky disco beat, they don't heat up. I didn't spen a lot of time on this, just pulled all codes and checked OASIS without any idea where to start looking until I can duplicate and verify the exact symptoms. Posted Image Any thoughts would be appreciated.

Bruce Amacker · February 26, 2009

I'm wondering if the "horrendous noise" is coming from the radio during the blink cycle due to a ground loop. Also, a ground problem would answer the heated seat issue. I'd first check the schematic for a ground that is common to these three circuits, locate it, and verify it is clean and tight. Keep an eye open for aftermarket accessories installed improperly where they may have drilled or screwed into a harness.

If this was in my bay, I'd do a ground voltage check. Run the engine, turn on all accessories, put your DVOM negative lead on the battery negative (you did check the battery terminals, right?) with a 20' extender, and probe every piece of metal in the car to check ground voltage. I probe the engine block, trans (even though it's bolted to the motor), manifolds, every module bracket, ig key, park brake bracket, seat mounting bolt, etc. Probe every piece of bare metal that you can lay eyes on in the entire car, even the trunk. No voltage reading should exceed .050VDC.

Make a mental note of voltages and if some are a bit higher, concentrate in that area. Pay strong attention to ground voltages in the circuits that are giving grief- find the grounds for the turn signals, radio, and seat heaters and test those.

While you're there, check your charging system AC voltage. Most are in the .02-.05VAC range with the motor running, of course.

Good Luck!

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