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Help! 1999 C-5 BAD B C M ?? OR TURN SIGNAL SWITCH ? OR ......?


Well-known member
Dec 18, 2008
87 z-51
suddenly my dash lites started to flicker, along with all the 'display lites' on the a/c control, stereo, and any other little letter or indicator lites.
The front day time marker lites are OUT, The front turn signals do not work but they both flicker fast. When I use the TS lever BOTH of the dash arrows lite up and both flash. When the dash is flickering I can hear a ticking from somewhere in the dash or near. Not loud, just a mild tic tic tic at the speed of flickering.
The front flashers BOTH flicker fast, not really flashing,,,,more flickering.
When I turn the parking lites or the head lites ON, the flickering on the dash STOPS, both arrows come on, stay on but the outside from is dark until a TS is used then it flickers again.

When I turn the Key to ON or RUN, all is normal for 5 seconds THEN the dash starts to flicker again. When I start it the same things happen.
The display for the, driver info seems to work, I CAN push the buttons to get gauges, trip miles, etc BUT the lite is flickering so its hard to read sometimes...

Does this sound like the BCM failing??? or the Turn signal lever shorted ??? or a short in the dash display ?

The ONLY thing that has been done lately is I installed sylvania silver star bulbs in the front running lites AND the blinker/marker lite about 2 weeks ago. Nothing else has been touched or changed. NO LED'S INSTALLED.
No,This sounds like a grounding issue............... grounds,Grounds,GROUNDS High Resistance or Non-Existent grounds make electronics do weird Sh*t!~! C5's have a bunch of them, Clean ALL of them.Splice packs and all!

Rob, Toms007, Tom Bryant ................. Somebody I can't find my Photos and Diagrams. Junk
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OK, I thoght about grounds but didn't think it was the cause since the symptoms are still there and consistent key ON eng OFF. The delay in the start of symptoms makes me THINK it's related to a module or ppackage of some kind...

Today I noticed the fog lites if turned on will flash when the headlamp switch is OFF.....going down the road everybody is waving and stopping me to tell me about it.......

BUT, when I turn the parking lites ON the flashing fog lites STOP flashing ! They stay ON.
No TS or marker. Rear TS still works no matter what.

It SEEMS that something is telling the dash & front markers & TS & fogs to flash. Not in every setting of the keadlite switch but some. IF the headlites are ON or parking lites are ON the dash stops flashing but the 2 TS arrows stay ON. BOTH will flash is I use the TS switch either direction.

I WILL got thru the grounds AND pull the BCM up to check for dampness under the module or water leaking in somehow...
grounds,Grounds,GROUNDS High Resistance or Non-Existent grounds make electronics do weird Sh*t!~!

I stand by that statement, I've repaired literally 100's of these cars with electrical problems,( C4's,C5's,C6's) 95+% without spending a dime on parts other than a can of CRC electronics cleaner, can of Boesheild and maybe a wire connecter or two. Fix one that has been hit by Lightning, Talk about a GROUND Nightmare!
Been There,Done That.......Just didn't wright a book. You want to talk in person PM me your phone # I can tell you the most problem areas of C5's to look. But when I get one acting like yours anymore,I just put it on stands,Remove the Battery, Lower Left F Fender Splash Sheild. Right & Left Kick panels ,Rt,&Lt trim panels behind the seats and start cleaning grounds Front to Back! If there is moisture in the floor compartment with the BCM, Your AC Udder is probly plugged and it's coming from the AC.

Don't hurt to clean all the udders in the cowel, Mine on the left side plugged last summer and flooded out my wiper motor. (3 on Left,2 on the Right) 1 behind the engine in the AC case.

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