Shared Knowledge
"BMW Z3 - Intermittent Turn Signal"
14 March 2014
Summary: most likely not steering column mounted turn signal switch but rather hazard relay in fuse box under hood.
Background:
BMW Z3: 1997, 2.8 liter, 60,000 miles.
Right side turn signal intermittent.
Turn signal circuitry: turn signal switch on steering column; turn signal switch connector to wiring harness under left side of dash; hazard flasher relay in fuse panel under hood and wiring harness connections to light assembly in rear and connectors for front side signals and signal in headlight assembly.
Most likely hazard relay:
Thinking was turn signal switch, bought new one from dealer $100+
To install new switch, had to remove: top and bottom covers over steering column and lower dash in left side of car.
Lower dash removal not easy because of foot well air duct work.
Noticed 3 relays attached to side wall of foot well.
Replaced turn signal switch.
Took apart old turn signal switch and very impressed with its construction both mechanically and electrically. No evidence of electrical or mechanical trauma. ????
Right turn signal still intermittent!!!
Removed turn signal socket from headlight and found it has a connector on it that connects socket to wiring harness. Cleaned contacts with electrical contact cleaner.
Cleaned contacts on both front side turn signal side markers.
Turn signal still intermittent.
Removed left side of dash again!
Removed the 3 relays there from their mounting and tried turn signal switch to find which one was flasher. None of them!!
Reinstalled dash.
Opened fuse box under hood. Markings for fuses but no indication of what relays in box were for.
Turned on turn signal and let it flash on left side.
Found turn signal relay was the tallest of the relays installed.
Shut down turn signals.
Removed hazard flasher relay.
Removing relay: push down on fuse box and pull relay straight up. At first appearance, looks like relay is held to fuse box by white thumb-press-in-clips, but this not true. Simply pull relay up and out.
With relay out of fuse box, cleaned all contacts with electrical contact cleaner and when dry, reinstalled into fuse box.
Note that relay will only go into fuse box one way.
Note how white arms stick up out of fuse box and sort of latch around bumps in sides of relay. Not held in place all that well.
Turn signals now not intermittent but if it happens again, going to replace flasher relay.
Note here: have had many cars over the years and every single one had electrical problems when fuse box mounted under hood. No matter how covered, under hood fuse box subject to moisture and thus contact corrosion.
Replacement flasher relay:
A replacement flasher relay from the dealer is $80 - $100.
Can buy a new one off eBay or from BMW Internet parts dealers for $30 or so.
eBay and Internet dealers part is by same manufacturer BMW uses.
Suggest you do not buy used. Any electrical contact that opens and closes as many times as the flasher relay does eventually results in electrical contact trauma. New is better.