The left turn cornering light for my 1990 has been out for some time.  Since winter has been so bad I am considering fixing it.  I am sure it is in the turn signal switch as I have tested out the circuit at the plug that is on the steeing column.  This is the last plug before going into the turn signal switch.  According to my manual, power comes from the head lamp swich and goes to the turn signal switch.  Since the right cornering light works but not the left then there must be power to the switch.  Since the wiring to the light checks out there is only one thing left-the turn signal switch.  Here is where it is getting confusing:  The manual says I have a 11 pin plug for the switch.  I look at the plug and there are 14 wires there.  I look at the picture for a new switch from Autozone and they have 13 wires.  If you look at ebay: 13 wires.  So I am not sure what the right answer is.  Anybody been here before?  Whats the chances the problem can be fixed without a new switch?

Is it just the cornering light? or the turn signal also?

The turn signals work fine.  Thats a " gotta have" in my book.

Can you run an ohms test of the power wire for the cornering light? the wire may be broken. Also check the plug I have seen the pins back out.

I applied 12volt power just upstream of the plug on the steering column and the cornering light works.  This test verifies the wiring and all known plugs and connections between the column and the light.  New information: I called the Wells "hot Line" and inquired.  They claim the turn signal switch (sw317) is the correct switch for the application.  They claim the matching GM number should be GM 1995974.  They indicated this could be on the connector itself.  No explaination was given as to why I have extra wires. v/r

Good detective work, Sounds like time to check the connectors. I would still want to know what the other wires went to, GM did not just add wires to nowhere!! Do you have a FSM to check the wiring?   Good Luck

The switch might fit other vehicles with different options, or accessories. As long as it has the wiring/terminal count that you need, and the connectors will plug up, you should be fine. It is strange that only one cornering light would fail due to a turn sig switch, but...stranger things have happened. Glad you got it figured out!

Once you get the new switch, I would suggest plugging it in first, and checking to see that everything functions as it should, before going thru the hassle of swapping them, and then finding out it doesn't work.

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|UPDATED|2/21/2014 7:28:41 PM (AZT)|/UPDATED|

More Information:  The 14th wire on the plug (turn signal switch side) is a ground wire.  The wire is about 8 inches long and connects to the steering column itself.  You can only "feel" the connection on the column.  The good news is that this should be workable with the 13 wire switch.  However it also begs the question of what was GM trying to ground on the other side of that plug?  Worst case is to by-pass the plug and wirenut the wire to ground as the new turn signal switch does not have a 14th connector pin.  Still seems like a lot of work (and risk) of going into the column for just the left cornering light, on the other hand we ARE vette owners, right?

The horn. The column has to be grounded for the horn buttons to work.

Here's a link to a diagram that you could use to make the cornering light work without repalcing the TS sitch.  I could do it in 20 minutes and $7.50 spent at JK Electronics with this circuit. I've used it for other things. It works.

http://www.the12volt.com/12voltimages/turninglights.gif