Fusebox/Dash/Firewall Wiring Problems

[Smellslike1974]

Okay guys,a lot to read but you need the details for this one. Ready for this?!

I am having issues with my wiring. My battery has been draining,leaving the negative cable off would help but I'm still losing juice. So since I am doing my oil pump this weekend,and other stuff I wanted to fix my problem with my gas gauge not working. My dad checked the fuses for me(I cant fit between the seat and steering wheel ) and he saw two blown buss fuses. Upon changing the one third down from the top it heated up and blew. This happened without having keys in the ignition. So for some reason I am getting direct battery from somewhere.The only new wiring done to the car has been a new starter cable from battery,my radio and I have my gauge trio & tachometer back light running to a cheesy switch so they aren't constantly lit when I don't need them).This problem has to be something someone did before me getting the car because I always had dead batteries before I took my car apart.

I looked the fuse up in question on a diagram and the wire is labeled "Black TR " and it goes to the heater switch.


Now as I was typing this post I decided to go take pics of everything in question regarding wiring. While I was I went and turned the key and with the one new fuse in and I now have a green alternator light which I never had before...ever! Also when I turned the key but not starting I heard wires or something arching under the dash.

The other buss fuse that was replaced I also looked up. From that it is a pink and black wire,which splits.The black goes to the "hazard flasher" then to the "dome light". The pink goes to the "stop light switch"

Obviously something is severely wrong because why would putting a new fuse in the hazard flasher,dome light,stop switch make my alternator light work?

Besides that problem there are two questionable wires on the firewall that I don't know what they go to.

This one located driverside near wiper motor. I'm not sure where it goes...(right lick,view image)


The other is on the passenger side left of the distributor. It looks like a ground but its a hot wire,thats why I have it wrapped in tape.(or since i have this wiring problem maybes its not suppose to be hot?)It comes from the harness behind the distributor.


Whether or not they are part of the problem I'm not sure.

Any ideas???

I know one thing I am definitely taking my seats out so I can actually see whats going on under the dash!

[sdweatherman]

Wiring simply sucks. Best thing to do is to print off the wiring diagram for your car off of the mymopar site and sit down and start tracing wires. The pink and black wires you mention are part of the bundle that runs back to the trunk area. Maybe someone altered the wiring back there for an amp or something? The issue with the blown fuse is interesting. You definitely have a direct route from the battery to ground on that one. Nothing but tracing wires and testing voltage and resistance with a multimeter is going to solve that one. Good luck! Scott.

[1bluegtx]

Well the one fuse that was blown goes to the heater blower switch then the blower motor resistor and then the blower motor,so one of those is bad (my guess is the motor)I would also unplug the taps you have to the acc. and bat. feeds on the fuse box till you figure this out.(Why is one green?)

BRIAN

[Smellslike1974]

Yeah I have already printed out a diagram over 4 pieces of paper taped together. I am thinking about framing it and hanging it in the garage.I'm gonna need it!

We unplugged the battery and accessory and still had the same problem. After hearing the noise when I turned the key I unhooked my battery completely.I don't trust the wiring now,nor do I want to have to charge it again.

The green wire is to the coil from my tachometer.I'm gonna take my seats out tomorrow and do some cleaning up of my wires as far as the gauges go.I'll keep you guys posted.

[Smellslike1974]

Okay well I unplugged the heater blower,heater switch and the relay(under the dash passenger side correct?)

I also used a volt meter on the positive side of number 3 fuse port.Its reading 12. After having no change un plugging the heater stuff we unplugged the 4 plugs on the back of the fuse box on the firewall. One of the 4 plugs contained a wire to the starter relay SO I finally went a got a new one but I still have the problem. My dad did find a red hot wire that was hitting the radio. We thought this was the problem but fuse port #3 is still blowing no matter what.

Does anyone have a pic of their starter relay.One of the extra wires i have is right near it but there isnt anything to plug into. I do know that Im gonna have extra because i converted to 4 brl carb

[1bluegtx]

Well on my 71 (which i would think is the same as yours)the number 3 fuse powers the dome and brake lights.Here is a wiring diagram (remember you are looking at the back of the fuse box notice the acc. and bat. tap locations)the heater would be fuse 7 on the acc. side:


BRIAN

[Smellslike1974]

No its not exactly the same but It looks familiar and is pretty much the same concept.Thanks for the pick though.
This Is the one I am going by:
http://www.mymopar.com/downloads/1974/7 ... unnerA.JPG

I have tried pretty much everything I can think of. I even just took apart my ashtray because my lighter was broke,thinking maybe that was the issue.

Is there suppose to be 12 volts going to that 3rd fuse port??
And by the way one of the plugs under the dash on passenger side to the heater looked melted,but with everything unplugged I'm still blowing a fuse.

Things I have done:

checked all wiring around where I welded patches in for destroyed/burned wires.
checked all wiring around where I added gauges,radio,tach,everything is sound and correct
In general I checked the wiring around the firewall making sure none were cut,bare,backwards,loose...Also around fusebox and where the previous owner butchered the radio wires.

I have a brand new starter relay now. Thought It was that,It is not.

Number 7 is working fine. All my lights work,dash lights,MY FUEL GAUGE WORKS NOW!,wiper motor works...

I am lost.

[73X]

How did you fit down there to get pictures of the fuse box?

[Smellslike1974]

I took my seat back out.

[road chicken]

Ok, let's get some basics out of the way here first.

When looking at the fuse block, there are two terminals at the bottom. One marked "batt". And the other marked "Acc". Those are short for battery and accessory.

Battery has power all the time, it is unswitched and has a direct feed from the battery, protected only by the fusible link .

Accessory is switched, it has power only when the ignition switch is in the "On" or "Acc" positions.

All the terminals directly above the battery terminal have battery power, ( inside left )

All the terminals directly above the "Acc" terminal have accessory power. ( inside right)

The terminal on the outside edges of the fuse block are where the circuit wiring connects and goes out to the cars various systems. ( outside left and outside right)

The fuses connect the power feeds ( inside right and left), to the circuits (outside left and right).

Also under the dash, you will see 3 port connectors in red, yellow , orange and black. Red is battery power, yellow are. Accessory power, Orange is dash / instrument light power. The black is for a specific circuit ground.I will give you some places to look and take measuments. Later, but for now, every terminal above the batt will have 12 v to ground on it all the time. The Acc terminals will have the same only when the key is turned on.

[Smellslike1974]

Thanks for that! I had a rough idea on how that all worked but wasn't sure of the details.The fusible link your referring to is the one running from the starter relay correct? I'll have to look for those wires you mentioned.

[road chicken]

Yes the fusible link is at the starter relay post, dark blue, about 4 -5 inches long and has a tab on it that says......you guessed it.. fusible link

[road chicken]

Ok

Looks like you can read the wiring diagrams and know how to use a volt / ohm meter. Do you have a test light too? Between those two you should be able to test most of what you need to.

Just to start with the heater fuse blowing.

Battery connected , no fuse in number 3. Check to see if there is voltage on the circuit side ( outside left ) terminal. Shouldn't be anything there volt wise. If 0 disconnect the battery. This is just making sure nobody wired around the fuseblock some how.

If you still have everything disonnected, go to Ohms and check between the fuseblock terminal (outside left). And ground...should be open / no reading at all. If it shows ground that wire is shorted b etween there and the switch plug. If ok ..

Plug the connector back into the switch and test again from the terminal to ground, should be open

[road chicken]

Check the switch in all positions. If anyone shows a resistance other than open, the switch needs to be looked at as it is probably toasted. The other possibility is one of the wires between the switch and resistor is shorted. Just check each wire to ground. This is not too common but it does happen occasionally If this checks out. Then it is probably the motor. If the resistor goes bad it just makes you lose low or medium fan speed.

Let me know how that works out.