Reverse Lights

[Schanen51]

Hey yall,

Haven't had backup lights since I bought the truck. To start, its a 700r4 trans. I've been diagnosing the problems as I've read from other threads that I've searched. I tested at the rear harness, and I get nothing. I tested before the harness, and still, nothing. The wires copper strands look to be corroded with a black look to them. Next, I checked the connection to my tranny. Everything appeared to be in order, but I wasn't sure whether or not to test the wires. I then check the neutral safety switch, and when I reached up to my column, I can't seem the locate any wires that are connected to the NSS (the terminals feel like there is no wire attached, and I got no fire with the tester). I tested the fuse, and there is fire to the fuse, which makes sense because my turn signals work. But anyway, where the hell do I go from here? At this point, I'm thinking of just rerouting it to a manual switch, but if possible, I'd like to get it right. So please good men of GMSB, any advice to get these things lit up?

 

[yevgenievich]

The switch at the base if the column should have wires for backup lights. Possible that it might jusy be unplugged

 

[Schanen51]

Thanks for the reply. I got up there and there is certainly nothing plugged into it... but isn't that was gives juice to the starter? I found a male plug that's not going to anything under my dash, but I'm not sure if it's the proper plug or not. Took pictures, maybe yall can help me identify.

 

[chengny]

Thanks for the reply. I got up there and there is certainly nothing plugged into it... but isn't that was gives juice to the starter? I found a male plug that's not going to anything under my dash, but I'm not sure if it's the proper plug or not. Took pictures, maybe yall can help me identify.

On the power to the starter solenoid:

Sometime ago (maybe late 70's or early 80's) the neutral safety switch was abandoned in favor of a mechanical lockout system in the upper steering column. There is a plate (maybe a sector plate) that has two slots. These slots align with the rack. The rack is what moves the ignition switch (via a rod) to it's various positions. The rack moves up/down within the column according to which direction the key is turned. The two slots will not allow the rack to move the ignition switch downward to the START position, unless the gear shift lever is in either P or N.

From then on the purple wire to the starter was a straight shot from the ignition switch to the S terminal on the solenoid - no color changes and no safety switches. If equipped with a manual transmission - then it comes out of the ignition as yellow and changes to purple after the neutral safety switch.

On the reverse lights wiring/switch issue:

When I initially read your post I did some research - mainly to provide you with the color of the wires that should be connected to the column mounted back-up lights switch. They are LT GRN & DK BLU, by the way.

Anyway, I was looking at wiring diagrams for the reverse light switch. When I found it I was surprised to see that incorporated into the same switch body as the back -up light switch was a P-N switch. I was interested as to what that switch was for. I looked at all the dwgs in 1987 & 1988 and all it ever said about the circuit was "used with auto transmission only". I did quickly find out that it is an input to for the ECM but never the actual purpose. But I was determined to find out. Went next to the service manuals and again the only explanation was that it is used "with auto transmissions only". I finally found a brief and rather vague explanation of it's purpose in the Driveability and Emissions manual. Here it is - and before I forget, the leads to the P-N switch are ORN/BLK & BLK/WHT:

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[Schanen51]

Chengny, you are the MAN. Thank you for sourcing those documents. Found the wires, rewired the plug and finally I've got fire to the reverse lights! Do you have any idea what that other plug I posted is for? Everything seems to be working, so I really have no idea what it's to.

 

[Bigred1985]

My reverse lights come on with ignition in my 1985 k30 I have no wires hooked up to the switch at the base of the column, lights do not go off ever until ignition is off..I have a 700r4 trans and am at a loss for what to do!

 

[Schanen51]

My reverse lights come on with ignition in my 1985 k30 I have no wires hooked up to the switch at the base of the column, lights do not go off ever until ignition is off..I have a 700r4 trans and am at a loss for what to do!

Bigred it sounds like the previous owner must have bypassed them somehow. Follow your wire that goes to your reverse lights (light green) and see where it takes you. You're going to need to go through that neutral safety switch for properly working reverse lights. If you can't track it, wire yourself up a dash switch so that you can at least shut the lights off while you don't need them and hit the switch when you go to backup.