Backup Lights

[mrmel2you]

I just noticed the backup lights on The Beast come on whenever the key is in the On/Run position or Accessory position.  Thought they only came on in the On/Run position, not both.  I put the shifter in Reverse, turn the key to On (engine off)--they come on (good so far)---put the key to Accessory--they come on (not so good, right?).  Wondering if this is a bug in the wiring, or if it was meant to be that way when it rolled off the line in '90?  

[cruiser54]

Check the switch on the transmission. Could be stuck.

[mrmel2you]

I replaced it last week when I replaced the brake light switch.  Figured I may as well, both might have been in there since new :)  Side note; it was doing this prior to replacing the switches.

[cruiser54]

Then the 2 wires going to the reverse switch are touching each other somewhere. 

[87MJTIM]

Based on your signature, you have a 2.5L, 4 sp.  Bear in mind, I am referencing he 88 electrical manual, but the power to the back up lights runs through the TCU fuse in the fuse panel.  That fuse should only get power when the key is in Run/Start.

 

Three parts that have power in Accessory mode are the blower, flashers and radio. (Lights are hot all the time.)

 

Focusing on the flashers, the only common connections are in the tail light harness.  So is a wire exposed in the tail that is making a contact with the BU lights?

 

(There is a additional wire that run on Access, but it stops in the back of the fuse box.  Unless a PO had tapped that at some time.)