Need a little help determining what is what on the firewall of this 72 duster. I am doing away with the factory distributor and I am attempting to locate the wire which will feed the new hei switched 12 volts. I am only getting 7-8 volts on the blue wire which feeds the ceramic resistor on the firewall on the drivers side upper corner. What can be elimintated from the firewall to clean things up?? Also what is the rectangular metal box adjacent to the brake booster?
72 duster firewall wiring questions ???
- Thread starter tnts72
- Start date
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So, upon some more electrical exploration. Turn signals will not flash, maybe only one click of the flasher pot when going from left to right switch position, sounds like it's somewhere up under the dash on the passenger side...? Lights are working just staying on solid. Wondering if maybe the previous owner put the wrong bulbs in?? Hazards will flash though... Horn currently does not work - horn will sound if I put 12 volts to it directly. More time with the fluke and searching wiring diagrams. I also noticed I am missing the clip / plastic bushing that connects the wiper arms together up under the dash on the drivers side...
67Dart273
Well-Known Member
You have a shop manual:
http://www.mymopar.com/index.php?pid=31
The 72 manual, by the way, actually came from this site, compliments of AbodyJoe
On the firewall you cannot really eliminate anything except the resistor. Basically you hook everything together that comes to the two ballast terminals, then use the original coil+ wire to feed the new system.
You MUST have all the wires connected. This is because the key switched "run" line goes dead during crank, and originally, fires up the brown that went to the coil + side of the ballast. That is the ONLY source of ignition voltage during "start."
http://www.mymopar.com/index.php?pid=31
The 72 manual, by the way, actually came from this site, compliments of AbodyJoe
On the firewall you cannot really eliminate anything except the resistor. Basically you hook everything together that comes to the two ballast terminals, then use the original coil+ wire to feed the new system.
You MUST have all the wires connected. This is because the key switched "run" line goes dead during crank, and originally, fires up the brown that went to the coil + side of the ballast. That is the ONLY source of ignition voltage during "start."
Thank you sir! I tried opening up that manual earlier and it wouldn't load. Will have to pull it up on my desktop and print it! Any idea what the 2"x3" metal box is on the firewall just to the right of the brake master cylinder? Has a small plug with a couple wires running into it.
MOPAR4Me
Well-Known Member
If it looks something like this, it is the voltage regulator.
MOPAR4Me
Well-Known Member
Sorry duplicate.
MOPAR4Me
Well-Known Member
Or like this.
Also planning to do the ammeter bypass wiring. Prefer to avoid said issues down the road if possible...
Still a little curious why I am going getting 7-8 volts on my blue wire that goes to the ballast resistor on the firewall when the key is in the run position... Any ideas other than tracking the wiring from the battery - through the starter relay - firewall connection - ignition switch - to the ballast resistor...? Car was running and driving before like this with the standard Mopar points ignition, just trying to find a good 12 volt source for the new HEI distributor before she shows up.
http://www.madelectrical.com/electricaltech/amp-gauges2.shtml
Still a little curious why I am going getting 7-8 volts on my blue wire that goes to the ballast resistor on the firewall when the key is in the run position... Any ideas other than tracking the wiring from the battery - through the starter relay - firewall connection - ignition switch - to the ballast resistor...? Car was running and driving before like this with the standard Mopar points ignition, just trying to find a good 12 volt source for the new HEI distributor before she shows up.
http://www.madelectrical.com/electricaltech/amp-gauges2.shtml
67Dart273
Well-Known Member
Check to be absolutely certain you are measuring the "key" side and not the "coil" side.
"Key" side should be same as battery, that is within a few tenths of a volt.
"Coil" side (with points closed or ECU "live") should be around 6--8V
There are only so many places you can be getting a drop..........
Before the Mad mod, .................
Big red feed through bulkhead connector..............connector at ignition switch.........switch itself.........back out bulhead connector on blue "ignition run" wire
so you need to visit all those "points" in the wiring and check them.
I've written many posts on this. If you ARE getting low voltage due to a bad connection, this LOW voltage will also cause OVER voltage when running because the regulator is sensing that low voltage and ramping up the alternator output until the "sense" point becomes 14V or so. Meanwhile the battery is way way above that
In other words, "whatever voltage drop" there is between battery and the VR, that what the VR will RAISE the charging voltage at the battery.
nm9stheham
Well-Known Member
You really need to trace it out and measure what voltage is where. If you don't, the problem will be there to cause you plenty of headaches. The bypass does not address this particular issue.
Feel free to put your readings here for further help/comment. It is a good set of measurements to make and can show a lot. Sure makes it easy to figure things out over the www
67Dart273
Well-Known Member
Well LOL it DOES address the issue if the bad connection "happens to be" the red /black main feed, and tearing it apart to perform the Mad mod just might show you the rest of the bad connections in there
rayer: thank you guys for taking the time to point me in the right direction! I will be spending some quality time with the meter / duster / manual over the next few days.Any chance you have a link 67Dart273 about replacing the feed wire to the igntion switch?
So I should complete the ignition feed wire fix prior to the Mad ammeter Mod - plan on picking up some pre tinned 10 gauge butt splices rather than using my standard insulated crimp splices on this job.
You guys recommend installing the fusible links as indicated on the MAD modification? 16 ga link on the 10 gauge black wire feeding into the the car for factory welded splice which then powers the ignition, and a 14 ga link section between the alternator and the starter relay? I should then also just eliminate the blue wire blade connection at the bulkhead the same way with or without a fusible link? Should it also be 10 gauge wire?
67Dart273
Well-Known Member
"Replacing the feed." Should not be necessary. You can buy the packard 56 terminals to replace bad ones in the bulkhead connector, or just string wire through there if you are not that fussy. I got mine from "clips and fasteners" online, they are something like "Aweco" (spelling?)
The thing is, it depends on "where" you are losing voltage. As I outlined........might be the bulkhead, the switch, or the switch connector. You just have to check them. So even if you replaced all terminals "it might be" right in the switch contacts.
In rare cases the ammeter or the "welded splice" is at fault. See the mad article diagram. The welded splice is up in under the dash in the black ammeter wire. It has failed in a few cases.
The thing is, it depends on "where" you are losing voltage. As I outlined........might be the bulkhead, the switch, or the switch connector. You just have to check them. So even if you replaced all terminals "it might be" right in the switch contacts.
In rare cases the ammeter or the "welded splice" is at fault. See the mad article diagram. The welded splice is up in under the dash in the black ammeter wire. It has failed in a few cases.
All the under hood is done. Alternator charging wire ran back and landed on positive terminal of starter relay with 14 ga fusible link @ the relay end. Red feed wire ran into interior cockpit through bulkhead with a 16 ga fusible link at the stater relay end. Blue wire underhood cut loose at 3 way splice and new 14 gauge
Wire ran through bulkhead into cockpit. Will remove instrument cluster tomorrow night to get access to the back of the ammeter and the ignition switch. I have been taking some pictures along the way. Pretty amazed how intact the wiring is on this old girl. Taking my time soldering and heat shrinking everything I get into in order to preserve all the originality that I can. Planning to install a 10 amp relay behind the instrument cluster somewhere to power the switched 12V ignition source for the new autometer dash. Thanks again and I will update this post as I go!
Wire ran through bulkhead into cockpit. Will remove instrument cluster tomorrow night to get access to the back of the ammeter and the ignition switch. I have been taking some pictures along the way. Pretty amazed how intact the wiring is on this old girl. Taking my time soldering and heat shrinking everything I get into in order to preserve all the originality that I can. Planning to install a 10 amp relay behind the instrument cluster somewhere to power the switched 12V ignition source for the new autometer dash. Thanks again and I will update this post as I go!
I did find it interesting that the blue wire under the hood is a 16 or smaller gauge wire but on the interior side of the bulkhead it's a 10-12 gauge...? Seemed strange to me?? I put a 14 gauge lead on it at the 3 way splice and was planning on running it all the way back to the ignition switch, but may keep the factory heavier gauge wire if the landed end is good @ the switch.
Sigh of relief! I have 12 volts on the brown wire!!! I completed the Mad Mod and ran a 14 gauge blue wire through the bulkhead while I was at it. Had to untape the looms while wire tracing and soldering / splicing under the hood and a little in the car. I also added a signal wire off the keyed 12 volts to actuate my new relay for the autometer dash. Once I get things a bit more tidied up I will put up a conversion thread. Thank you guys for the advice and the wisdom! So much more to learn about these Mopars, one thing at a time. Feel like I owe you guys a beer at least!
One tip for those who don't already know, soldering iron does a great job of securing the heatshrink tubing in the presence of other wires you don't want smoked. Those of you that already do this please disregard - old maintenance trick I figured I would put out there for those that maybe don't know.
nm9stheham
Well-Known Member
BTW, make sure each of your wires that are soldered are well supported a few inches from the solder joint. The reason is that solder will wick into the wire strands and create a 'hard spot' in the wire just outside the connector into which they are soldered. This hard spot is where any bending force on the wire due to vibration will concentrate and can work harden the soldered wire just outside the connector, and eventually break it with the regular vibration of car operation. (This is from direct experience in a race car.)
Glad your brown wire voltage is solid now; that is good for the future of your car.
Glad your brown wire voltage is solid now; that is good for the future of your car.
67Dart273
Well-Known Member
Now that you've made all this progress you STILL (sorry!!) need to check if you are "in the zone."
That is, STILL might be voltage drop in the ignition switch or it's connector
Clip your meter to the blue "ignition run" wire. Do so with everything hooked up "normal" as you want current drawing on the igntion / VR / field circuits
Hook the remaining meter probe to the battery POS. This will measure voltage drop directly. With the key in "run" but engine stopped you are hoping for a very low reading, the lower the better. More than about .3V (3/10 of a volt) you need to pay attention to ign switch and connector
Another "way around this problem" is to have the blue "run" wire key a relay, and feed your underhood loads off that.
Voltage drop in this circuit causes OVER charging, because the VR has to make up for it, and jacks up the voltage at the battery.
Excellent points by both of you guys, I was planning to just use my small zip ties and loom the wires back up. Thinking I may end up wrapping them back up like they were, should support them better and give them some bit of protection... Just a bigger pain when rerunning / tracing any other electrical issues down the road. I will measure the voltage drop as you specified. I hope a second relay installation is not required, but it can be done if necessary. If I do have to install that relay just use the switched blue wire as my trigger and power the relay off the positive terminal on the starter relay?
Only thing I plan on running under the hood on the keyed 12 volt circuit would be the new HEI distributor. Just trying to figure out where I would break the blue wire to feed the relay. Would have to be after the blue / brown splice in order to not lose the 12 volts to the relay when cranking.
Terminal layout
30 outbound 12 volt terminal
85 Relay ground
86 Keyed 12 volt signal wire
87 Source power from battery positive on starter relay
Any of you guys ever use WAGO Wall Nuts?? Pretty handy for multiple wire splices like this keyed 12 volt deal
Only thing I plan on running under the hood on the keyed 12 volt circuit would be the new HEI distributor. Just trying to figure out where I would break the blue wire to feed the relay. Would have to be after the blue / brown splice in order to not lose the 12 volts to the relay when cranking.
Terminal layout
30 outbound 12 volt terminal
85 Relay ground
86 Keyed 12 volt signal wire
87 Source power from battery positive on starter relay
Any of you guys ever use WAGO Wall Nuts?? Pretty handy for multiple wire splices like this keyed 12 volt deal
To add that relay could I just cut the brown wire back I plan to use for the distributor and run it to the relay as the trigger and power the distributor off the relay which would be fed 12 volts from a wire off the starter relay + battery terminal...? That would be pretty simple, but would it fix the voltage drop if there turns out to be one? Sorry if it seems like I am kind of thinking out loud here...#-o
67Dart273
Well-Known Member
No you want to trigger the relay off the blue coming out of the bulkhead, (electrically) CUT the blue and then use the relay to feed the blue loads. You could actually hide the relay under the dash, and wire it in from there
If you mount it under the hood, yes, feeding the relay fused from the starter relay is a good plan.
If you mount it under the hood, yes, feeding the relay fused from the starter relay is a good plan.
Will most likely keep it under the hood just so its accessible in the future if I need it for any reason or if it ever needs replaced.
Think I understand what I need to do here:
1. Cut blue wire on engine side of bulkhead and plug into Terminal 86.
2. Supply 12 volts from starter relay positive post to terminal to 87 on relay.
3. Connect end of Blue wire leading up to Blue / Brown splice to output terminal 30.
4. Ground relay terminal 85.
Honestly this is probably a good thing to do anyway even if the voltage drop isn't more than .3V? Nothing saying a loose connection could not develop over time resulting in an overcurrent situation. The relay would prevent such such an occurance from creating a potentially serious issue like a burned up Duster...rayer:rayer:
Think I understand what I need to do here:
1. Cut blue wire on engine side of bulkhead and plug into Terminal 86.
2. Supply 12 volts from starter relay positive post to terminal to 87 on relay.
3. Connect end of Blue wire leading up to Blue / Brown splice to output terminal 30.
4. Ground relay terminal 85.
Honestly this is probably a good thing to do anyway even if the voltage drop isn't more than .3V? Nothing saying a loose connection could not develop over time resulting in an overcurrent situation. The relay would prevent such such an occurance from creating a potentially serious issue like a burned up Duster...
rayer:rayer: -
