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Interior turn signal bulbs fine; fuse fine; but left bulb won't work

Started by Oshroshr, May 18, 2014, 06:21:20 PM

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Oshroshr

have changed out fuses and checked bulbs. Why won't dash turn signal display work?
Outside signals work. H OShell

TJ Hopland

I don't have my books handy at the moment but since that was still an older body style (79-85) I would assume it was still like the earlier stuff where there were fusible links off the battery wire at the starter.   Typical for GM in the 70's and early 80's (which I am assuming this is) was 3 link wires.  One was to the headlight switch for the headlights.  One was to the fuse box for the stuff that stayed on all the time.  Last wire was to the ignition / key switch which then powered the rest of the fuse box for the stuff that came on with the key.

The fusible ink wires were typically about the first 18 or so inches of the wire off the starter.  They then spliced into regular wires and joined the rest of the under hood harnesses.   Being down by the starter and exhaust there is plenty of opportunity for damage especially if a starter was changed at some point and the mechanic did not take the time to get all the guards and wires back in their original locations. 

It was the mid 80's that they started doing the double stacked positive battery cables where one cable went to the starter and the other went to a distribution point where I think the alternator also connected.   I assume they still then used the fusible link wires but I am not sure what the distribution was.   After that design they went to the fuse / relay box under the hood in addition to the fuse box in the dash.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Oshroshr

Thanks for answering.  I will look and probably have more questions.

Oshroshr

Now have changed fuse.  Also changed out a few bulbs.  But question. The turn signal light in the dash on left side still doesn't work after changing bulb. What else could it be?

Commodore

Does the left hand front park/turn signal light work? If it does you have a bad left hand turn signal indicator socket or wiring. The turn signal indicator gets its power from a splice on the wire going to the front park/turn signal light.

KD

Ken Dennison

1935 Auburn S/C Cabroilet
1940 Cadillac V16 7 passenger Imperial Sedan (9033)
1929 Ford Closed Cab Pick Up
1960 Austin Healey Sprite

76eldo

Does the indicator light work when you use the 4 way flashers?

It is a bulb and it can fail. Also the socket gets its voltage from a ribbon cable like a printed circuit board. Either one can be faulty.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

bcroe

If I understand, the signal works, but not the dash indicator.  These are all
getting power from the same source.  There were plenty of problems with
poor contacts in those days.  If it was the signal/brake light, I built up the
solder bumps on the bulb to increase the spring pressure.  In the dash, the
first problem was dis similar metals increasing contact resistance from the
slow chemical reaction over time.  I clean & this time solder everything. 
Individual bulbs were mounted in a holder which twisted in place and made
contact.  Unfortunately the mounting material changed and got uneven
from pressure and/or bulb heat over time, no longer making reliable contact. 
I soldered a small flexible wire from each side of the bulb holder to the mounting
board; now the board contact didn't matter.  However, put it in backwards
and the wires will short the circuit out. 

cadillacmike68

If the bulb is known to be good, and the fuse is good (and if the other indicators like the actual front and rear turn signal lamps for that side are all working), then it is wiring - somewhere.

Check for voltage at the bulb and work back or from the harness and work forward.
Regards,
"Cadillac" Mike