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JuStIcELiVeS · 11-01-2009, 11:11 PM

I am having trouble getting backup lights to work on my 79 400 auto. Bulbs are good, wiring looks ok, and I have just replaced the neutral/safety switch on the transmission but still nothing. Truck starts (or won't without switch connected) and wires do not look to have been modified in any way. Anyone else know what I should look for next?

justin · 11-01-2009, 11:13 PM

Are the sockets getting power when put in reverse? Could have a bad wire or loose ground somewhere along the line. May even be a bad socket...you can get them now from most parts stores.

Break out the test light or multimeter and start from the beginning.

JuStIcELiVeS · 11-01-2009, 11:21 PM

Thanks Justin. I was thinking the same but since my I already executed the bad idea of just replacing the switch ($40 lost apparently), I thought it best to start asking question being I don't see wiring issues jumping out at me. I will check this and reply back.

justin · 11-01-2009, 11:27 PM

Its pretty hard to diagnose wiring issues online, sometimes you just gotta jump in head first.

Your NSS could be out of adjustment, if you search you'll find instructions on how to set it correctly. After that, have a friend put the truck in reverse and put a test light in the bulb socket and see if you are getting power.

Break out your Haynes manual and start testing wires until you find the problem.

JamesH · 11-02-2009, 06:08 PM

Make sure you take a wire brush to all of the ground connectors in your lighting system (including the ones at the rear lights). That worked for me (scrub the metal that they attach to as well as the actual face of the electrical connector that bolts to the sheet metal).

JuStIcELiVeS · 11-02-2009, 09:43 PM

Cool, thanks guys for the tip. I had checked the bulbs already and found nothing wrong visually. I went back with a Fluke as Justin mentioned and sure enough, there was power making it back to both sockets even though neither one lit. I figured that I had made a mistake with the NSS switch so I swapped back in the old one temporarily and found it was indeed not functioning so I will stick with the new one. I finally got one side to power a bulb after cleaning up contacts. They didn't appear to be in bad shape but that it made all of the difference. Once socket puts out power but won't light a bulb no matter how much I scrub so I will probably replace it as well as clean up the ground. Thanks again for the tips!

justin · 11-03-2009, 07:24 PM

They sell new sockets with a few inches of wire in most parts stores in the bulb/electrical section. I think they were about $5-6 a piece. There are a few different styles so make sure to get the number off of it or take it to the parts store with you.

11-01-2009, 11:11 PM	#1
JuStIcELiVeS Registered User Join Date: Nov 2009 Location: Johnson City - NY Posts: 3 iTrader: (0) Bronco Info: 1979 Trailer Special - 400/C6 JuStIcELiVeSs Garage	Backup lights not working I am having trouble getting backup lights to work on my 79 400 auto. Bulbs are good, wiring looks ok, and I have just replaced the neutral/safety switch on the transmission but still nothing. Truck starts (or won't without switch connected) and wires do not look to have been modified in any way. Anyone else know what I should look for next?

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Backup lights not working

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11-01-2009, 11:21 PM	#3
JuStIcELiVeS Registered User Join Date: Nov 2009 Location: Johnson City - NY Posts: 3 iTrader: (0) Bronco Info: 1979 Trailer Special - 400/C6 JuStIcELiVeSs Garage	Thanks Justin. I was thinking the same but since my I already executed the bad idea of just replacing the switch ($40 lost apparently), I thought it best to start asking question being I don't see wiring issues jumping out at me. I will check this and reply back.

11-01-2009, 11:27 PM	#4
justin Registered User Join Date: Jul 2003 Location: Columbia, SC Posts: 4,582 iTrader: (21) Bronco Info: 96 XLT/5.0/E4OD justins Garage	Its pretty hard to diagnose wiring issues online, sometimes you just gotta jump in head first. Your NSS could be out of adjustment, if you search you'll find instructions on how to set it correctly. After that, have a friend put the truck in reverse and put a test light in the bulb socket and see if you are getting power. Break out your Haynes manual and start testing wires until you find the problem.

11-02-2009, 06:08 PM	#5
JamesH Registered User Join Date: Mar 2005 Location: Charlottesville, VA Posts: 83 iTrader: (1) Bronco Info: 1979 Ford Bronco, Built 400 JamesHs Garage	Make sure you take a wire brush to all of the ground connectors in your lighting system (including the ones at the rear lights). That worked for me (scrub the metal that they attach to as well as the actual face of the electrical connector that bolts to the sheet metal).

11-02-2009, 09:43 PM	#6
JuStIcELiVeS Registered User Join Date: Nov 2009 Location: Johnson City - NY Posts: 3 iTrader: (0) Bronco Info: 1979 Trailer Special - 400/C6 JuStIcELiVeSs Garage	Cool, thanks guys for the tip. I had checked the bulbs already and found nothing wrong visually. I went back with a Fluke as Justin mentioned and sure enough, there was power making it back to both sockets even though neither one lit. I figured that I had made a mistake with the NSS switch so I swapped back in the old one temporarily and found it was indeed not functioning so I will stick with the new one. I finally got one side to power a bulb after cleaning up contacts. They didn't appear to be in bad shape but that it made all of the difference. Once socket puts out power but won't light a bulb no matter how much I scrub so I will probably replace it as well as clean up the ground. Thanks again for the tips!

11-03-2009, 07:24 PM	#7
justin Registered User Join Date: Jul 2003 Location: Columbia, SC Posts: 4,582 iTrader: (21) Bronco Info: 96 XLT/5.0/E4OD justins Garage	They sell new sockets with a few inches of wire in most parts stores in the bulb/electrical section. I think they were about $5-6 a piece. There are a few different styles so make sure to get the number off of it or take it to the parts store with you.