backup lights, neutral safety switch problem - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72freak · 01-23-2006, 08:44 AM

When I built my 1972 Suburban I used the running gear and wiring harness from a 1990 model Suburban. The transition went flawalesly (almost). One of the few problems I have yet to work out is the backup lights. I believe on the existing 72 harness and neutral safety switch.....the backup lights only get power when the truck is put in reverse. Well, on the 90 harness and switch it works the other way...the back up lights are hot all the time and the switch completes the circuit. (I think) Atleast this is how they are working at the moment. Example....when it is all plugged up......the reverse lights stay on all the time and when I put the truck in reverse....the lights go out. I have swapped the wire on the plug going to the switch and that didnt work, I looked into switching the neutral safety switch thing to the 90 model one but that wont work. I have also looked into taking the 72 switch appart and re-working it on the inside and ofcouse there is always re-wiring the entire back up curcuit.

Have any of you had this problem? Is ther an easy fix?

Luvlegs · 01-23-2006, 09:02 AM

If you have the 72 column still, is there a chance you had it in reverse when you set the switch in place on the column? (and it might be backwards?) I don't know if its possible but could the switch be on the wrong side of the linkage that makes it "move over" when going to reverse? Hard to describe but when on the floor facing the truck, the switch sits on top of the column at the floor/wall. I wonder if you lifted it off, and either turned it around or put in any other gear (other than reverse) and set it back down, it that might not take care of it...... Just a thought...

72freak · 01-23-2006, 09:23 AM

Quote:

Originally Posted by Luvlegs

If you have the 72 column still, is there a chance you had it in reverse when you set the switch in place on the column? (and it might be backwards?) I don't know if its possible but could the switch be on the wrong side of the linkage that makes it "move over" when going to reverse? Hard to describe but when on the floor facing the truck, the switch sits on top of the column at the floor/wall. I wonder if you lifted it off, and either turned it around or put in any other gear (other than reverse) and set it back down, it that might not take care of it...... Just a thought...

The factory neutral safety switch has not been removed nor has the column. I have put the muti-meter on the switch and checked it against another spare I have and the switch and column seem to be workng properly. Its NUTTS!!

Also...if you look at the inside of the neutral safety switch on the 90 model and compare it to the inside of the 72 model...the contact points are different...They are infact made backwards of each other. Thats why I figured the 2 sytems worked backwards of each other?!?!?!

Luvlegs · 01-23-2006, 10:01 AM

When the lights are on, can you trace the power back to the bu switch? Then pull the plug off and see if the power drops off? Any chance someone else might have unhooked/rehooked something in the circuit during the build? Are the bu lights on without having the headlights or markers on?
Neutral safety switch = back up lights switch (in this instance) right? hmmmmm...

**pjmoreland** · 01-23-2006, 01:06 PM

The backup lights just have one wire going to them, which provides 12 volts to the bulbs, and the ground is provided through the light housing to the body, right? I don't have a schematic for your '90 harness, but I'm wondering if there is a relay that powers the backup lights that is inverting the voltage going to the lights. Could that be the case? If so, you could track down the relay and bypass it, and connect the wire from the reverse/neutral-safety switch directly to the backup lights. Or you could add another relay to invert the signal again.

01-23-2006, 08:44 AM	#1
72freak Rottenwood Garage Member Join Date: May 2005 Location: Marietta, Georgia Posts: 4,321	backup lights, neutral safety switch problem When I built my 1972 Suburban I used the running gear and wiring harness from a 1990 model Suburban. The transition went flawalesly (almost). One of the few problems I have yet to work out is the backup lights. I believe on the existing 72 harness and neutral safety switch.....the backup lights only get power when the truck is put in reverse. Well, on the 90 harness and switch it works the other way...the back up lights are hot all the time and the switch completes the circuit. (I think) Atleast this is how they are working at the moment. Example....when it is all plugged up......the reverse lights stay on all the time and when I put the truck in reverse....the lights go out. I have swapped the wire on the plug going to the switch and that didnt work, I looked into switching the neutral safety switch thing to the 90 model one but that wont work. I have also looked into taking the 72 switch appart and re-working it on the inside and ofcouse there is always re-wiring the entire back up curcuit. Have any of you had this problem? Is ther an easy fix? Attached Images

01-23-2006, 09:02 AM	#2
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: backup lights, neutral safety switch problem If you have the 72 column still, is there a chance you had it in reverse when you set the switch in place on the column? (and it might be backwards?) I don't know if its possible but could the switch be on the wrong side of the linkage that makes it "move over" when going to reverse? Hard to describe but when on the floor facing the truck, the switch sits on top of the column at the floor/wall. I wonder if you lifted it off, and either turned it around or put in any other gear (other than reverse) and set it back down, it that might not take care of it...... Just a thought... __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

01-23-2006, 10:01 AM	#4
Luvlegs Registered User Join Date: Sep 2005 Location: Smith Mountain Lake Virginia Posts: 1,537	Re: backup lights, neutral safety switch problem When the lights are on, can you trace the power back to the bu switch? Then pull the plug off and see if the power drops off? Any chance someone else might have unhooked/rehooked something in the circuit during the build? Are the bu lights on without having the headlights or markers on? Neutral safety switch = back up lights switch (in this instance) right? hmmmmm... __________________ "A cat will almost always blink when hit between the eyes with a ball peen hammer" (you don't always have to state the obvious) Wear your PPE! You can eat with false teeth but you can't see with a false eye. 1959 Studebaker Silverhawk 350/400 1972 C10 L6 3OTT 2005 F350 - Built - whew!

01-23-2006, 01:06 PM	#5
pjmoreland Senior Member Join Date: Jan 2005 Location: CA Posts: 5,400	Re: backup lights, neutral safety switch problem The backup lights just have one wire going to them, which provides 12 volts to the bulbs, and the ground is provided through the light housing to the body, right? I don't have a schematic for your '90 harness, but I'm wondering if there is a relay that powers the backup lights that is inverting the voltage going to the lights. Could that be the case? If so, you could track down the relay and bypass it, and connect the wire from the reverse/neutral-safety switch directly to the backup lights. Or you could add another relay to invert the signal again.



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