W140 Sudden Electrical Gremlin, any ideas?
 

It never ends....

Driving to work this morning, start merging into left turn lane. Hit turn signal, doesn’t come on. Battery and ADS light both come on. Radio goes off. Car keeps running, no signs of hesitation or stalling. Pull into lot, leave engine running. Speedo stuck at 38 mph, and Tach stuck at 1,250. Shut engine off, heard regular clicking (relay?) from trunk. Was able to pop trunk, but by the time I got to the trunk I could not hear the clicking anymore. Went back inside the car. Tried turning ignition on again, noticed that caution lights did not all illuminate as usual. Some did, others didn’t. ADS light stays on.

Went back out after researching on Forum...didn't find too much.

Opened door, no interior lights. Speedo and Tach still stuck. Clock stopped. Hazard lights don’t work. Trunk release works. Fuel gage zero. Started car, no problem. Battery light on, Fuel gage still zero and Low Fuel level light on. Oil level light on, oil pressure gage zero. ADS and Seatbelt lights on.

Pressing Hazard switch turns off all the caution lights except ADS light, and does not turn Hazard lights on. As soon as Hazard switch is released, caution lights come back on. Turn signals still not working. Climate Control works. Radio working, but stays on without key. Door close assist works. Rear window heater does not stay on. Light in rocker switch comes on, but won’t stay toggled on. Rear shade works.

I need to check fuses, battery voltage, Combination relay, and pull codes tonight.

Anybody have any thoughts on this?

wow!
 

you just sent a chill down my spine.obviously it's electrical.the first thing i thought of was main loom deteriorating but then i noticed that you have the V12 engine so i figured no way that was usually for the six cylinder models.then , while i'm writing this i realize that the V12 is like two sixes together , so maybe it is the wiring harness.klimas and the like don't apply to our model so i would suggest you check the wires and look for cracks in the wire sheathing or missing insulation altogether.good luck, keep us informed.

What's that famous. . .
 

. . line from that movie??? "they're back"!

Sounds more "looms" gone bad under dash . . . :confused:

Was driving across wilds of Kansas when suddenly cruise control disconnected.

Then, radio stopped.

Got to small town, where turn sigs didn't work.

Electrical system was shutting down due to low voltage.

Didn't start again once turned off ignition.

Needed new alternator.

Good car to get me to a town.

Yes, good . .
 

. . point! A low battery w/ a failing altenator will do that for sure!

Good thoughts everyone.

Wires under the hood look good. As some of you know, I rewired the AMM's and passenger ETA. Balance of wires look newer or in good shape.

I've had the dash apart a few times in the past, including pulling the instrument cluster out. All wires looked good. Nothing like those near hot stuff under the hood.

Battery was replaced 7/28/05. Voltage measured 12.75 with car off, right after short run. I will check alternator output voltage to see what alternator is doing.

Started the car repeatedly with no problem.

No codes other than those left over from my rear duovalve rebuild. Cleared those, they're gone now.

I'm suspecting the Combination Relay (N10, N10/2). This item controls wipers, hazards, turn signals, instrument cluster indicator lights, and rear window heater. I pulled it out of the fuse box, and examined the myriad of wires down inside the box. They also look very good. Can't see a way to get the N10 open to see what the insides are about. Also can't find a test procedure to see if it's working right. Whatever is going on, it's intermittent. Instrument cluster is back to life, along with turn signals and hazards.

Anybody know how to test the Combination Relay? Will start new thread with more specific title. Thanks Everyone!