Duster back up lights

[IMNCARN82]

So this has been like this since I got it. I've looked a bit and found no shorts so far.When I put it in reverse the alt. gauge drops really low.Lights dim. I have no backup lights.(they never worked)Checked bulbs.Sometimes the CD player goes off until I get it in Neutral. Figured it was a short somewhere. Any ideas?  Also it's fine most of the time but sometimes it will drop low at idle at night with all the lights on. Alternator seems to be working. It always starts right up.  Anyway...   I just suck at electrical.

1975 Duster /6  auto. all original.   Thanx electroguru dudes      R/T

[Bullitt-]

Seems to me the problem has to be either the transmission neutral/back-up switch or wiring from there to the backup lamps.  If you follow the wiring from the rear forward http://www.mymopar.com/downloads/1975/75DartB.jpg it starts out violet at the lamps goes into a plug position #6 changes to white & runs to the bulkhead connector position A http://www.mymopar.com/downloads/1975/75DartA.jpg where it changes to black & ends at the tranny.  Power is shared with the radio & heater fan so if those loose power at the time I'd think there is a short to ground(surprised your not blowing the fuse) .  You should be able to use an ohm meter to isolate the problem, with the car off disconnect any plug & see if there is continuity from the wiring to ground, to check the switch place the tranny in reverse.  It's even possible the problem is in the bulb or socket so inspect/check there also.

[dodj]

To narrow it down quickly, I would first pull apart the plug with terminals 1 to 8 (disconnects all the rear wiring) and start the car and put it in reverse. If the problem goes away, check all the wires, sockets and bulbs from the plug to the rear of the car. If the problem still exists, put the plug back together and unplug the bulkhead connector with terminals A-H. Start the car and put it in reverse and see if it still happens. Probably won't. Check the physical condition of the two black wires from the bulkhead connector to the reverse sw on the tranny - they often get burned by the exhaust. If the problem didn't go away with the second test, the bulkhead connector or wiring close to it (interior side) needs to be checked out. 

[IMNCARN82]

uh ok yeah what he said...               I'll read those two posts 20 more times.Then maybe...      Nice and easy. Deep breathes. 

Thanks ALOT!   

[IMNCARN82]

So I just unplugged the back harness in the trunk. Started it up and now the problem is gone.I've gone over the lights,sockets.About to shred the wire wrap.Nothing seems damaged,cracked,burnt,ect..   But it's got to be there...          I'll git that little bugger...     

[IMNCARN82]

Couldn't find any wiring problems.Kept looking at the slightly busted pass. tail light housing...(The brake light side)Decided to try a better one that I was saving for after paint. Now it's fixed!!! Got backup's!!! WOO HOO!!!     THANKS!!!   

[Bullitt-]

Good Deal....What I call Laying Hands On, sometimes that's all it takes.

[IMNCARN82]

The funny thing is I went everywhere else looking for the problem.There it was right in front of me.      First-over complicate it,Then locate the problem. 
Oh well...It's working!!!      Now if I can just figure out a way to get the drivers side defroster tube back on the dash.         Sometimes it's the little things that mean the most. Thanks again for the push. This place is da BEST! 

[dodj]

There it was right in front of me.     

Thats what makes electrical stuff so much fun  It's invisible 

[Bullitt-]

  Now if I can just figure out a way to get the drivers side defroster tube back on the dash. 

If I can recall from 30yrs ago, pull the instrument cluster out & it should be right in front of you. 

[IMNCARN82]

well the backups work,But it still drops sometimes.Not as bad. it's weird.   I'm still searching. Is it normal for the alt. gauge to drop in gear at idle with all the lights on?Now it goes down about 1/4 way...One line down on the gauge.Never a problem in Drive.If only at a stop sometimes. Hmmm... 

[dodj]

Is it normal for the alt. gauge to drop in gear at idle with all the lights on?Now it goes down about 1/4 way...One line down on the gauge.Never a problem in Drive.If only at a stop sometimes. Hmmm...

That would be 'normal'  ......although you can improve it with relays and ammeter bypassing.

[Bullitt-]

Did the radio drop out go away?  If not I think you still have an issue on that circuit.
As for the discharge at idle I have experienced this and was able to all but do away with by burnishing all contacts from the alt. to the voltage regulator to the battery as well as all grounds to body. You do have a ground strap from the RH head to the firewall?. At some point I also replaced the brushes in the alt.  At idle except with a heavy load, headlamps ++, my ammeter will sit steady in the middle. 

[IMNCARN82]

yea the radio drop out went away. It doesn't drop low enough now.  I'll clean up some more connections. Yes it has the ground strap to firewall. I have another alt. here I might try. Just because this one looks to be pretty old.  It's like a time warp under the hood.  THANKS for all the help you guys!!!