wiring check

[moparfanatic56]

I am attempting to check the functions of all my electrical components prior to installing the motor in my 72 dart. I have all new m&h wiring harnesses through out the entire car. I put the battery in connected the red power wire from the bulkhead and a power wire from the battery to the starter relay on the inner fender. I currently only have the headlights and wiper motor that are functioning and nothing else no taillights, brake lights, dome light, side markers etc. Am I missing something else, at first I thought it was because I forgot to put the fuses in but the headlights and wiper motor worked without them. Any thoughts or help will be appreciated. Thanks

 

[Dana67Dart]

Some circuits are fused some are not.


Also grounds must be attached for many things ( lightbulbs,) to work.

 

[67Dart273]

Is this a "factory like" harness? Is the ammeter still wired up? If so, observe if it deflects with the headlights.

If that is so, not sure. As above, fuses?

What do you have the battery grounded to?

 

[Mattax]

I have all new m&h wiring harnesses through out the entire car. I put the battery in connected the red power wire from the bulkhead and a power wire from the battery to the starter relay on the inner fender. I currently only have the headlights and wiper motor that are functioning and nothing else no taillights, brake lights, dome light, side markers etc.

It would seem that there is a mismatch with the interior connections. Whether the mismatch is with the bulkhead connections or the key switch, is the question.
This assumes a standard wiring harness, not a option fleet or similar modified arrangement.

connected the red power wire from the bulkhead and a power wire from the battery to the starter relay

According to my cheet sheet below for '72, this should provide power to the headlight switch and items connected to the 'always hot' fuses in the fusebox. This includes parking lights, horn, and dome light.

If you have a voltmeter or test light, check the feed connection in the fusebox (12 or 14 gage red with white stripe).
Normally wipers get power from the switcxhed 'accessory' feed. Will need to check that with the '72 FSM


Although not relevant to your immediate problem, this terminal is not a great choice for the battery feed.

A

 

[moparfanatic56]

Is this a "factory like" harness? Is the ammeter still wired up? If so, observe if it deflects with the headlights.

This is the m&h harness from year one supposedly factory repro. The ammeter does deflect when I turn headlights on

If that is so, not sure. As above, fuses?

Checked fuses all good.

What do you have the battery grounded to?

Currently to the radiator support, maybe should go to frame rail?

 

[Mattax]

You have wipers.
Lets see how the 1972 Plymouth Service Manual diagram shows the power to the wiper switch.

B on the switch indicates power. regardless of the actual source of power alternator or battery, its always marked B or Batt.
2 in a diamond indicates a welded splice.
Q2 is switched accessory.

So key off, no power should be reaching the wipers.

 

[67Dart273]

I'm beginning to think there is something wrong with the harness. Review this simplified diagram, which is from the ammeter bypass article

Catalog

Bear in mind this is simplified.

In a stock harness, the main feed for the interior comes off the big stud of the relay, through the fuse link, and through the bulkhead on ammeter BIG RED. Through the ammeter, out the ammeter on BLACK, and to the WELDED SPLICE a few inches from the ammeter. From that splice, the BLACK branches off, depending on year

TO headlight switch
TO ignition switch power feed
TO fuse panel hot buss
TO bulkhead connector and out to alternator output stud

So get into your fuse panel, which, (factory) has THREE busses. 1 is hot at all times, 1 is hot only in "run" or "accessory" and the last is hot ONLY when the light switch is feeding power to the INST fuse for the dash lamps.

So find out if one buss in the panel is HOT always, and if not, find out. Check if the other is HOT with key in "run" or "accessory" and if not find out why

 

[moparfanatic56]

ok

I'm beginning to think there is something wrong with the harness. Review this simplified diagram, which is from the ammeter bypass article

http://[URL]http://www.madelectrical.com/electricaltech/amp-gauges.shtml

[/URL]

View attachment 1716093588

Bear in mind this is simplified.

In a stock harness, the main feed for the interior comes off the big stud of the relay, through the fuse link, and through the bulkhead on ammeter BIG RED. Through the ammeter, out the ammeter on BLACK, and to the WELDED SPLICE a few inches from the ammeter. From that splice, the BLACK branches off, depending on year

TO headlight switch
TO ignition switch power feed
TO fuse panel hot buss
TO bulkhead connector and out to alternator output stud

So get into your fuse panel, which, (factory) has THREE busses. 1 is hot at all times, 1 is hot only in "run" or "accessory" and the last is hot ONLY when the light switch is feeding power to the INST fuse for the dash lamps.

So find out if one buss in the panel is HOT always, and if not, find out. Check if the other is HOT with key in "run" or "accessory" and if not find out why

ok I dropped the fuse box and checked all of the leads that connect to the individual fuses on the back of the fuse block for voltage. I had 12 volts on all but the instrument, tail lights and cigarette lighter/ dome light. When I did the check the key was in the run position and the headlights were on. I did depress the brake pedal but they did not light up so I am guessing that the switch is either bad or I have the wires on the wrong plugs.

 

[67Dart273]

Forget the INST. The cig lighter/ dome light etc should be hot at all times. I'm beginning to wonder---either the harness is mis wired or the big splice in the black ammeter wire is broken.--Assuming it is actually "like the factory." Is there any larger feed wires like no 12 that you cannot account for?

You should be able to LOOK at the rear of the fuse panel and see the busses. They will be large brass pieces attached to one end of the fuses. As I said, one section will be "hot" only with key "on" and the other should be "hot" at all times.

The "key on" one feeds stuff like radio, heater, turn signals, that comes on with the key

 

[harrisonm]

I cannot answer for a 72 Dart, but the brake lights on a 69 Barracuda go through the turn signal switch. After a complete restoration about 9 years ago, I was going to take the car for a test drive, but there were no brake lights or turn signals. After hours of testing and looking at a wire diagrams, I found that brake lights and turn signals both went through the turn signal switch. I replaced the turn signal cancelling cam (TSCC) with a new (turned out to be garbage) part. On the back side of the TSCC, there are four metal prongs. or wires, that make contact with different copper nodes on the turn signal switch depending on the position of the turn signal lever. It turned out that those prongs/wires were not making contact with the nodes. So I bent each wire down (away from the TSCC) so they could make contact with the nodes. Everything was fine after that.

 

[67Dart273]

Is there any documentation with that m&h deal? Is is supposed to EXACTLY match factory wiring

If so you need to get ahold ( if you don't) a 72 manual, which you can download, free, from MyMopar.com

 

[67Dart273]

This is a shot out of the factory manual of the fuse box Look at "D" and "E" and the bar above it. This is the 'hot' buss. Go up and see wire Q3-14R. This wire (factory) goes to the big splice at the ammeter. Again that should be "hot" all the time.

We know the ammeter is getting power because the headlights work and you say the ammeter deflects. This comes from the same place. If you cannot resolve it, I would call the supplier of the harness. Otherwise, plan on disconnecting the battery, pulling the cluster out, and unwrap enough of the harness to find the ammeter (black) wire splice.

 

[moparfanatic56]

Ok so about half of the problem is solved, the red wire with the white stripe was unplugged on the backside of the fuse block. I now have park lights and brake lights but still do not have instrument lights. I checked the voltage for the instrument lights on the fuse block and no voltage there. I tried the turn signals but they did not work but the emergency flashers did, this a new harness also.
I apologize for all the questions but as you can probably tell electrical is not my strong suit. I deeply appreciate all of the help.

 

[Mattax]

he red wire with the white stripe was unplugged on the backside of the fuse block

STOP! DISCONNECT THE BATTERY!

I apologize for all the questions but as you can probably tell electrical is not my strong suit.

That's fine, but you've ignored the help I've provided.
If you do not know how to read the diagram that I posted, then ask.
You must disconnect the battery and leave it disconnected untill you have connected and secured all of the hot terminals so they do not accidently touch the body metal. In a similar vein, remove any wedding bands or similar metal jewlery from your hands when working on a car with the battery connected.

The way to use the diagrams is like a map.
Put your finger on the Battery positive. That's the power source. Follow the line representing the connecting wire.
Eventually it leads to a black circle. That represents a welded splice.
Every wire connected to that splice is at battery voltage.
Touching the bare terminals of any of the wire to ground will result in the battey discharging the highest current it can through the connection.

When the battery is connected these are always hot

There is no off switch for these wires.
The only protection to break a short to ground is the fusible link, and the wires that have fuses.
In the best case scenario the link will melt quickly and there will only be minor damage elsewhere along the path.
Reality is the link is a 16 gage wire and it may not melt quickly.

 

[moparfanatic56]

STOP! DISCONNECT THE BATTERY!



That's fine, but you've ignored the help I've provided.
If you do not know how to read the diagram that I posted, then ask.
You must disconnect the battery and leave it disconnected untill you have connected and secured all of the hot terminals so they do not accidently touch the body metal. In a similar vein, remove any wedding bands or similar metal jewlery from your hands when working on a car with the battery connected.

The way to use the diagrams is like a map.
Put your finger on the Battery positive. That's the power source. Follow the line representing the connecting wire.
Eventually it leads to a black circle. That represents a welded splice.
Every wire connected to that splice is at battery voltage.
Touching the bare terminals of any of the wire to ground will result in the battey discharging the highest current it can through the connection.

When the battery is connected these are always hot
View attachment 1716093764

There is no off switch for these wires.
The only protection to break a short to ground is the fusible link, and the wires that have fuses.
In the best case scenario the link will melt quickly and there will only be minor damage elsewhere along the path.
Reality is the link is a 16 gage wire and it may not melt quickly.

I did disconnect the battery before I plugged the red/white stripe wire back in, I also taped the alternator wire to pevent any metal contact there.. I am also understanding the diagram you posted but I am still at a loss as to why I do not have any voltage at the instrument light fuse. So correct me if I am not thinking the right way with this, I have power for the headlights but not the instrument panel lights, shouldn't the power for them come through the headlight switch which is hot constantly? I am trying to contact m&h to see what they think. Thanks again for your help and I apologize for my ignorance with this.

 

[67Dart273]

Here is how the INST lights work and it is a trick.

First, the HL switch has TWO power sources. One comes from the welded splice/ammeter wire and goes to B1, powering ONLY the headlights

The second power source is from the tail light fuse, goes to B2 at the switch, and powers tail, park, and INST lamps

The tail power........

when the switch is in park or head, and when the dimmer knob is twisted somewhat to the left, goes through the dimmer control, OUT on the tan wire and down TO the INST fuse. Through that fuse, and out to all dimmer controlled dash lamps on ORANGE wires.

1...So the park/ tail circuit has to be working
2....The switch has to be on
3....The dimmer control has to be somewhat to the left (CCW)
4....And for the dash lights to work the INST fuse has to be good.

 

[moparfanatic56]

Here is how the INST lights work and it is a trick.

First, the HL switch has TWO power sources. One comes from the welded splice/ammeter wire and goes to B1, powering ONLY the headlights

The second power source is from the tail light fuse, goes to B2 at the switch, and powers tail, park, and INST lamps

The tail power........

when the switch is in park or head, and when the dimmer knob is twisted somewhat to the left, goes through the dimmer control, OUT on the tan wire and down TO the INST fuse. Through that fuse, and out to all dimmer controlled dash lamps on ORANGE wires.

1...So the park/ tail circuit has to be working

The park/tail lights are working

2....The switch has to be on

So if the headlight switch is on I should have voltage at the instrument fuse correct?

3....The dimmer control has to be somewhat to the left (CCW)

I set it there but not all they way to activate the dome light.

4....And for the dash lights to work the INST fuse has to be good.

Checked continuity and it is good.

 

[moparfanatic56]

ok I contacted m&h and he says to check the headlight switch primarily the tan wire coming out for power. I will go with this and see what happens and let you all know the outcome.

 

[moparfanatic56]

ok, I am back again. I bought a new headlight switch and in the park position and the knob most of the way to the left i have my 12 volts at the fuse but still no instrument lights. Now when I turn the knob all the way to the right I lose my voltage at the fuse. My next question is does that ipv module (or whatever it is called) on the back of the instrument panel have anything to do with the lights.

 

[67Dart273]

Twisting to the right WILL kill power to the fuse. Re-read what I posted. The tan wire and INST fuse GETS power FROM the dimmer control. So if the dimmer control is not providing power, there will be no power to the INST fuse. From here you just need to chase the lamps. If you have LED lamps check polarity---most will not work if the sockets are turned 1/2 turn.

 

[moparfanatic56]

I gotcha now, in my feeble little mind I was thinking turning to the right would make the lights brighter its been 40 years since I messed with an older car. Now for the bulbs they are new but the old style not led and the bulk of the sockets are new also. So could I possibly be looking at a bad circuit board?

 

[67Dart273]

Maybe. If you can solder you can fix many of them, but most lamp / board problems are loose pins on the harness connector at the board ----clean and solder, clean up the board traces where the sockets contact, clean the socket contacts and bend the things for more tension, and run a separate ground pigtail from a ground point on the board to the dash frame or column support bracket. You can see where they ground just follow the traces,and there are several screws on the board mounting you can attach to one of

 

[Dana67Dart]

. Now for the bulbs they are new but the old style not led and the bulk of the sockets are new also

Did you get 1/2" or 5/8" sockets?

The 5/8 are the correct ones.

Also the dash has to be grounded for most of the lights to work

 

[moparfanatic56]

Did you get 1/2" or 5/8" sockets?

The 5/8 are the correct ones.

Also the dash has to be grounded for most of the lights to work

I did get the 5/8 sockets. I pulled the cluster out of the dash and did a continuity test. I followed the traces to the pins for the dash lights, turn signal lights and high beam indicator lights. I had continuity for the right turn signal and high beam indicator light but none for others. I wasn't sure about checking the oil pressure and brake light or the other gauges as they run to the voltage limiter. So are my pin connections bad?

 

[67Dart273]

See if they wiggle. If so clean and solder. I told you earlier, or tried to. Figure a better way than continuity checks. WHY? Because very low resistance, such as switch contacts and wire terminals, and connectors, are very hard to evaluate with continuity. Much better is to learn to use VOLTAGE DROP UNDER LOAD

Consider a VERY simple circuit--a 2 cell flashlight, spread out on a bench, 2 cells, a switch, and the lamp. Here's what you have

At ground to the shell, you have the spring terminal at the battery negative, either 1 or 2 trouble spots right there

Between the two cells, 1 more connection for trouble.

The connection from the battery + to the lamp, yet 1 more trouble possiblility

The connection from the lamp shell to the switch, yet one more trouble point.

Finally, the switch ground to the shell--making a round circuit

EACH 1 of those trouble points, PLUS the possibility of 1 or 2 bad / poor/ batteries, as well as the switch contacts, all "additive" trouble.

Imagine this all laid out on a "breadboard" circuit, with everything accessible.

The lamp is dim, maybe intermittent. How do you find? Pick a spot, such as the battery +, and move your VOLT meter probe along each point. Wherever there is drop, there is a problem.

For example, if you put one probe of the meter on the battery + of the two, and your other probe on the - next to it, there is nothing there except the connection of the two batteries. If it is corroded, dirty, loose (not enough pressure) you will measure more drop, the worse it gets.

Obviously, measuring across each cell will show the drop in voltage under load, and here, you want MORE V instead of less, showing that cell is in better condition/ charge.

THE FACT IS that with VERY LOW resistance circuits, resistance / continuity checks can really REALLY get you down the wrong road.

They are good for a "quick check" if you are looking for say, a bad lamp bulb, and such. But when you really get to digging into things, I rarely use resistance.