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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: buildanother]
#869950
12/03/10 12:14 AM
12/03/10 12:14 AM
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Joined: Jan 2003
Posts: 5,444
So Cal
Sinitro
master
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master
Joined: Jan 2003
Posts: 5,444
So Cal
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Quote:
Wiring and/or alternator problem. The alt has to charge to blow things out.
Sounds like the alternator threw out a very high voltage such as 18V if the regulator or something internal shorted for a split second driving it up. Note that fuses typically blow on current overload not voltage overload..
Just my $0.02... 
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: shamefulcuda]
#869952
12/03/10 01:49 AM
12/03/10 01:49 AM
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Joined: Sep 2003
Posts: 1,168
Vancouver, WA
MoparMarq
super stock
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super stock
Joined: Sep 2003
Posts: 1,168
Vancouver, WA
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Quote:
I would love to fix the problem with the lights coming on only in run, except I have no idea at this point. I realize wiring problem somewhere but keep in mind, I have been up and down this harness now, and Im not seeing any added splice. I have found 2 splices but wire was put back (in other words looks like it was broke and properly repaired).
It may look to be properly repaired, but looks can be deceiving. I hope you have a FSM to follow along on the schematic. My FSM is '72, so may be a little different. The feed to the HL switch is 12 gauge black to terminal on switch labelled B1. If, for whatever reason by PO, it was cut or replaced to be supplied only in run (maybe they ran down the battery for some reason), he might have used a dark blue ignition feed wire from somewhere in the harness to replace the black feed for the HL switch. If so, that would explain the on-only-in-run phenomenon, and explain the flicker at idle due to no charge from alternator and nature of power use by coil.
Additionally, if the dark blue wire he used was the one that goes out to terminal 23 on the bulkhead connector, that MIGHT explain why the VR gets low power and therefore doesn't allow the alternator to charge, even though the harness on the engine side of the bulkhead connector is new and in perfect shape.
Quote:
So nothing has been added in the harness. The engine bay harness is new. I will keep at it tomorrow, was hoping someone has encountered this. From what I can tell checking alt , it is not charging the car.
I may be out in left field here with what I described above, but a few things can be checked pretty easily. I assume the car runs fine without the lights on (except for the charging issue). With the car not running, but the key in "run", see if there is power to the blue wire on the electronic VR harness. There should be, if the car runs. If not, something is goofy with the new harness, and I'm at a loss. The problem is probably in the cabin side of the dash harness with the hot (black wire) factory splices and ignition feed (blue wire) factory splices. Maybe one of the black wire splices went bad at some point with the PO, and he pulled power for the HL switch from whatever he found that had power with the key on.
I'm really curious about what you find with this. I've never heard of it before. Good luck.
-Marq
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: shamefulcuda]
#869954
12/03/10 02:15 AM
12/03/10 02:15 AM
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Joined: Sep 2003
Posts: 1,168
Vancouver, WA
MoparMarq
super stock
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super stock
Joined: Sep 2003
Posts: 1,168
Vancouver, WA
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Quote:
I thought about the high voltage and so what I did is disconnected the bulkhead connector (1st plug in closest to master cylinder) to sort of eliminate the alt and charging system and that didnt change a thing. Rear taillights were still flickering with the idle of the car. I didnt dare rev it up as I didnt want to burn another set of bulbs (they arent cheap anymore)
'71 must really be different than '72, 'cuz if that connector is disconnected on a '72, it won't run (no power to VR or ignition coil). If the harnesses are the same between years, or nearly so, you've got something weird going on if your car still runs with the harness disconnected...
I'm really at a loss to figure it now...
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: shamefulcuda]
#869955
12/03/10 02:17 AM
12/03/10 02:17 AM
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Joined: Sep 2003
Posts: 1,168
Vancouver, WA
MoparMarq
super stock
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super stock
Joined: Sep 2003
Posts: 1,168
Vancouver, WA
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Quote:
What does PO mean? Drawing a blank on that.
PO = previous owner
OP = original poster
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: shamefulcuda]
#869957
12/03/10 04:39 AM
12/03/10 04:39 AM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
mopar
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mopar
Joined: Oct 2010
Posts: 606
Montana
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It's too darn late tonight to think clearly, but I think you have a problem in the bulkhead/ ammeter/ underdash in harness splice." I believe that a wiring fault has disconnected the battery from the alternator feed so that the lights are drawing power from the alternator, but the alternator is not connected to the battery. Check carefully in that area If that splice has broken loose in the harness, it's possible that part of the conductors are connected to the alternator feed, and part of them are connected to the battery For example, my '70 book shows that the black wire from the ammeter AND the feeder for the headlight switch both terminate at that splice. I'd be considering untaping the black ammeter wire until you find that splice I posted this out of my 67 manual because it's pdf  If you find the ammeter to the far right, note "R6A-12BK" at the bottom of the alternator and trace it back, where all that stuff comes together is a big splice "in harness." Now notice that L1-16-BK takes off to the lower right of the splice, and runs right down to the headlight switch. THIS IS the main feed that runs the lights. If somehow, that splice came apart in such a way that some of the car was "being fed" power and other parts were not, this could explain what's goin' on. (In my lifetime, I've found three cars that had one of those spliced fail. First one, I remember, was a buddies 68 Roadrunner--the ammeter would dance all over hell. We were sitting in the car in a driving rainstorm, the harness and dash all over our laps. I found it and fixed it, and he just could not believe it.)
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: shamefulcuda]
#869958
12/03/10 05:40 AM
12/03/10 05:40 AM
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Joined: Mar 2007
Posts: 3,281
West Coast, USA
jbc426
master
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master
Joined: Mar 2007
Posts: 3,281
West Coast, USA
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Why don't you start by putting a volt meter on the alternator and see whats going on there. Measure with the car off, with it idleing and s-l-o-w-l-y bring up the rpm's. It shouldn't go any higher than 14.4 volts.
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: jbc426]
#869960
12/03/10 02:28 PM
12/03/10 02:28 PM
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Joined: Oct 2010
Posts: 606
Montana
Yancy Derringer
mopar
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mopar
Joined: Oct 2010
Posts: 606
Montana
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Quote:
Why don't you start by putting a volt meter on the alternator and see whats going on there. Measure with the car off, with it idleing and s-l-o-w-l-y bring up the rpm's. It shouldn't go any higher than 14.4 volts.
This won't work if there's some sort of wiring problem that separates the battery. The regulator sense may well be operating from the battery, and so the regulator "thinks" the voltage is low, and has the field ramped up trying to charge the battery
(We used to run into this with those %%%%%% diode battery isolators when they failed. They would charge the heck out of the auxiliary battery, but the main would be going dead. There's been at least one boat had a bilge explosion because of them)
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: Yancy Derringer]
#869961
12/03/10 08:22 PM
12/03/10 08:22 PM
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Joined: Mar 2007
Posts: 3,281
West Coast, USA
jbc426
master
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master
Joined: Mar 2007
Posts: 3,281
West Coast, USA
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Quote:
Quote:
Why don't you start by putting a volt meter on the alternator and see whats going on there. Measure with the car off, with it idleing and s-l-o-w-l-y bring up the rpm's. It shouldn't go any higher than 14.4 volts.
This won't work if there's some sort of wiring problem that separates the battery. The regulator sense may well be operating from the battery, and so the regulator "thinks" the voltage is low, and has the field ramped up trying to charge the battery
(We used to run into this with those %%%%%% diode battery isolators when they failed. They would charge the heck out of the auxiliary battery, but the main would be going dead. There's been at least one boat had a bilge explosion because of them)
It will tell him the voltage at the alternator to start with. There's a whole series of test that need to take place in a systematic fashion, but first things first.
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: Yancy Derringer]
#869963
12/03/10 10:39 PM
12/03/10 10:39 PM
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Joined: Sep 2003
Posts: 1,168
Vancouver, WA
MoparMarq
super stock
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super stock
Joined: Sep 2003
Posts: 1,168
Vancouver, WA
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Quote:
I know exactly what you said, what I'm saying is, IF IF IF IF the problem is something on the wiring as I described, THE ALTERNATOR VOLTAGE WILL BE IRRELEVANT and may in fact be "very high."
READ IT AGAIN. If a wiring fault has disconnected the alternator output from the battery, and left the voltage supply to the regulator IGN terminal going to the battery, then the regulator will "think" the battery is low (which it WILL be) and will ramp up the field current, causing a HIGH voltage condition at the alternator output. IT WILL NOT BE nominal 13.5-14.5 V, it WILL BE in fact much higher and CAN in fact cause this very problem.
I go with this analysis also. It may be in the splice indicated above, OR, looking at the schematic for '72, he may get lucky. I believe it could be just on the inside of the bulkhead connector on terminal 18 where the alternator output comes through the bulkhead connector to feed that splice. It's possible that pushing the new harness on from the engine side pushed the terminal out of the bulkhead connector on the cabin side. If so, it'd be relatively easy to replace the terminal with one from an electrical parts store with the proper barb on it to retain it in the bulkhead connector sleeve location.
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Re: Headlight/ Electrical problem 71 Road Runner. HELP
[Re: MoparMarq]
#869964
12/04/10 04:13 AM
12/04/10 04:13 AM
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Joined: Mar 2007
Posts: 3,281
West Coast, USA
jbc426
master
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master
Joined: Mar 2007
Posts: 3,281
West Coast, USA
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I understand what your saying, and it could be that or a bunch of other things. I just like leaving all the if's, the maybe's, the might be's out of it and begin with a logical series of tests to see what is actually going on. Testing and troubleshooting have always served me well.
1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
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