Back-Up Light Fuse blowing Question:

[Captain D]

Hello all,

It seems that we keep having our back-up lights fuse blow every time we install a new one. The car runs and drives perfectly fine, all the lights, switches, etc. all work fine as well - but for some reason the fuse furthest to the left inside the glove box keeps blowing out and no back-up lights. The last one I recently took out even showed a hint of a burn mark.

I recently had the transmission rebuilt and the plug on the transmission is good, I then checked the wires that run along the sill plate from front to back of the trunk area and everything is good to go too. At first, we began to notice that every so often it would give out but now, all I have to do is to start the car and 'thar she blows.'

Since its getting worse, is there anything else that I can check before it affects some other aspect of the car? The only thing that I had installed recently was a gauge cluster voltage regulator/limiter but I would think that something like this is unrelated. There is a big event coming up in just 2 weeks so I'm looking to get it straightened out before then for sure.

'Thank you' for any and all replies,
Aaron

[resq302]

Aaron,

When you say, you start the car and it blows right then, do you mean you start the car and it immediately blows or does it blow right after you put it into reverse?  If you do not have a factory service manual or a factory wiring diagram, I would strongly urge to purchase one!  They are worth their weight in gold!  IF you do not have one, I would try unplugging the back up lights and see if it then blows the fuse.  If not, you know the problem lies in the back up lights themselves.  If it still blows, you have to trace it back further.  Is your car an automatic or manual.  If it is a manual, try unplugging the back up switch on the trans and see if that still makes the fuse blow.  If you have an automatic, you might not be able to do this due to it having the neutral safety switch involved. 

Was it doing this before you had the instrument cluster out?  If so, chances are it is not related to anything you did with the installation of the voltage limiter.

[Captain D]

Hi Brian,

Thank you for your reply. Unfortunately, I do not have a manual yet - but I'm seriously thinking about getting one as soon as possible,  . As for my 69,' it is an automatic on the column and it kept blowing the fuses when put in reverse. I took your suggestions in unplugging the lights from the cluster. When I started, I disconnected the battery, then disconnected the lights from this terminal plug on the cluster, and then finally removed the old fuse in the glove box.

While the wires for the lights were disconnected from the cluster, I took some very fine sandpaper and gently cleaned up the terminal prongs behind the cluster and sprayed a little contact cleaner on both the wiring harness plug itself (since it looked a little dated) and the retainer clips that actually hold the fuse in place before re-installation of everything that I disconnected. To check the fuse in stages, I turned the key to the 'on' position (checked it), turned the engine over (checked it), and then I put the car in reverse and the fuse was holding fine for a change,  . I would think that if the problem was the back-up switch on the transmission - no matter what I did elsewhere on the car - either it would work or it wouldn't so that's why I'm thinking that its not this particular switch (but I could be wrong). I'm unsure if this is a genuine or band-aide fix or not, but before, it kept blowing as soon as I would put a new fuse in. Maybe I just wasn't getting a good contact in these areas that I just cleaned up...?

If it happens again, you are suggesting to unplug the wiring harness terminal for the lights (behind the cluster) and then start the car to see if the fuse blows without it being plugged in, is that right?

'Thank you' again for your time and guidance,
Aaron  

[Nacho-RT74]

being 69, IF the back up switch its at the tranny, I would check the NSS harness underneath the floor for some short with chasis. Tht's not hard to happen with this harness due the exhaust heat

[resq302]

That reminds me, I have to change out my back up switch on my trans.  The reverse lights haven't been working and would have to play around with the shifter in reverse ( take it in and out a couple times) in order to get the reverse light to come on under the dash.  Could be from lack of use the switch got some dirt or rust starting on the spring loaded ball and is causing the issue with not making a circut on my issue.  Easy fix though!  (hopefully)

[Captain D]

Nacho - That's a good point; something that I will definitely look into and keep in mind.

I'll run the car and see how well the fuse holds out. If I do end up having to replace the back-up light switch for the transmission, I've seen some sell for about $40 on average at Advance Auto, Auto Zone, NAPA, etc. But, before I jump on one is there one in particular that you guys would recommend (727 automatic w/ electronic ignition), just out of curiosity? I remember some good advice on the RTE limiters and didn't know if there is a switch that everyone recommends over another in like fashion.  

resq302 - Hey Brian, when you go to replace yours, please let me know how things go and any tips on how to go about doing it so that I can learn, if you could please.  

'Thank you' again for the replies,
Aaron

[resq302]

Aaron,

From what I remember (as I have had to replace it before) it is just like a giant bolt with an electrical connector on the end.  Very similar to an O2 sensor.

[john108]

This may be un-related but I had a problem with lights blowing fuses.  I traced it to the side marker light wire at the right front fender.  The wire was jammed between the fender and the framing attached to the fender behind the headlights.  It looked like the wire was routed that way at the factory.  The insulation wore away and there went the pop.

[Cooter]

Also, make sure some ding-dong didn't install a double contact bulb in a single contact socket. Wouldn't believe how many times this happens.

[b5blue]

Aaron your saying the fuse blows when not in reverse? 

[Captain D]

Hi gents - I apologize for the delayed reply (been puttin' in a few extra hours in at work),

But, yeah, its back to the drawing board - I went to put it in reverse to follow up on it and the fuse was blown again,  . It seems that all of the wires are all in good shape and I cleaned up the terminals, but maybe I just need to replace the back-up light switch for the transmission to see if that makes a difference or I'm getting a bad ground. If it was a poor ground since its blowing so quickly, where are the best places to look for something like this on the car before I go out and buy something new altogether?

Thank you again for any and all replies,
Aaron

[Nacho-RT74]

as I said, I bet is a broken or peeled off cover on one of the outer wires or plug to NSS. One of them must be energized allways with key in RUN or ACC... the other one just when put in reverse. Central is actually the NSS wire.

Do you want a try before get underneath the car ? unplugg harness to NSS at bulkhead, replace fuse and put it on reverse again... if doesn't blow, then problem is on that harness

[Captain D]

Hi Nacho - I'm glad that you reminded me about this area on the car, thanks man, and I think that you may be right about double checking the wiring harness under the car.

I had a little time to go under before I had to leave for work in order to get a closer/better look and, sure enough, there is a spot on two wires (at the same point) that are both fully exposed due to the heat of headers, more than likely. I'm off tomorrow and will see if I can carefully separate the two wires to individually re-wrap them and then both together before installing a new fuse altogether.  

Good info on unplugging the harness too in order to check a new fuse - I will spend the day tomorrow on it and let you know how things go  .

High regards,
Aaron

[Captain D]

Hi all,

Just to touch-base with everyone who posted and offered to help me out - I repaired the spot on the two wires right under the car (and above the left-side headers) a few days ago that I had mentioned in my last posting and so far the back-up lights have been working just fine with no blown fuses,  . Many 'thank you's' to everyone who posted under my thread - all good info and I enjoy learning about this stuff for future references  .

High regards,
Aaron    

[resq302]

glad you got the car fixed Aaron.  Now we just have to figure out what is going on with mom's challenger that started eating up distributor rotors!     you pass your gremlins on to us?   

[b5blue]

  Pop the dizzy cap and grab the rotor off the shaft. Hold the dizzy shaft and I'll bet it will move from side to side if you try moving it sideways. I had a new A-1 Cardone rebuild with a bushing so worn it was insane, total junk. The next one (And last A-1 Cardone part I'll ever buy.) had an advance that was so crapped up the rotor flopped around back and forth just spinning it with your hand.

glad you got the car fixed Aaron.  Now we just have to figure out what is going on with mom's challenger that started eating up distributor rotors!     you pass your gremlins on to us?   

[resq302]

Ok, pulled the distributor apart last night while I was at my parents house.  Shaft is perfectly straight and not bent.  Everything that I took out I put back the same way and nothing was put back wrong.  What appeared to be happening was that the pressure from the spring steel contact was causing the rivet to come out of the hole which held the two pieces of metal together.  (the spring steel piece and the tip that went and made the spark to the tower).  I think what was happening was that the cheap arse Carquest brand rotor plastic was heating up and would cause the rivet to loosen up.  the new BWD (I think its Borg Warner) is a LOT thicker and more solid / heavier gauge plastic.  Hopefully this was the problem as every rotor that went bad was the Carquest brand one.

The rotor is fully seated into the notch and the circular spring clip is back under the felt pad which I put a drop or two of oil on as I think that is a wick of some type.  So far, everything seems ok, of course, the other rotors were in and ran fine right away too.  Time will tell!

[Nacho-RT74]

so I WAS RIGHT!!! LOL

[resq302]

so I WAS RIGHT!!! LOL

I dub thee, new name of Sir Nacho- Mopar Guru of the electrical gremlins!        

[Nacho-RT74]

LOL... was a joke... I'm not a guru of anything!!! just sharing experiences.

Good you got to find the problem!