Newbie accessory question

-

stank71

Member
Joined
Mar 17, 2020
Messages
23
Reaction score
2
Location
Elma, Washington
So I have had many Mopars throughout my life but this time I am finally going to finish one. At least that is the plan. I have a 1968 Plymouth Valiant that has a /6 and no ac. I am going through the car entirely, and plan on putting a 360 in in it. I am working on the cabin now, and I am going to pull the dash harness and check/replace the wiring. My question is this:

I have purchased aftermarket Bluetooth stereo, power window kit, power lock kit, an aftermarket underdash AC set up and a universal cruise control. Do I need to add a separate fuse block for all of these? I do not know very much about auto electrical components. I suspect the load on the existing 52 year old setup was not intended for all the add ons. Is it safer to have a separate fuse block for the accessories? How would I do that? Any help and advice would be appreciated. Thanks FABO!
 
So I have had many Mopars throughout my life but this time I am finally going to finish one. At least that is the plan. I have a 1968 Plymouth Valiant that has a /6 and no ac. I am going through the car entirely, and plan on putting a 360 in in it. I am working on the cabin now, and I am going to pull the dash harness and check/replace the wiring. My question is this:

I have purchased aftermarket Bluetooth stereo, power window kit, power lock kit, an aftermarket underdash AC set up and a universal cruise control. Do I need to add a separate fuse block for all of these? I do not know very much about auto electrical components. I suspect the load on the existing 52 year old setup was not intended for all the add ons. Is it safer to have a separate fuse block for the accessories? How would I do that? Any help and advice would be appreciated. Thanks FABO!
The only safe way to do it. Maybe @Mattax can chime in. He's real sharp on this stuff.
 
Yes, I would add a fuse block, fused, off of the battery. And run new wires to all the added accessories.
 
I wouldn't run anything off the battery directly.
The ones that will be used when the engine is off, I might tie in with a terminal post.
The ones that will be used when the engine is running above idle speed, I might tie to the alternator output with a terminal post and/or additoinal fuse box.
You could use the empty accessory fuse slot in the existing fuse box - if the currents will not be too high.
There is only one slot there, so it can't be used for things that you wan to work with the key off, and also work with things that should work with the key on.
Each accessory should have the power it will need listed somewhere. It may be in Watts, it may be be in amps at 12 or some other voltage.
Get all that information and you can start planning a design for adding them on.
I think it likely to make sense to use one of the optional power feed wiring methods. And it almost certainly means using a later alternator.

Basic power circuits for 67 is explained in this post so read that first.
headlights not working
 
I wouldn't run anything off the battery directly.
The ones that will be used when the engine is off, I might tie in with a terminal post.
The ones that will be used when the engine is running above idle speed, I might tie to the alternator output with a terminal post and/or additoinal fuse box.
You could use the empty accessory fuse slot in the existing fuse box - if the currents will not be too high.
There is only one slot there, so it can't be used for things that you wan to work with the key off, and also work with things that should work with the key on.
Each accessory should have the power it will need listed somewhere. It may be in Watts, it may be be in amps at 12 or some other voltage.
Get all that information and you can start planning a design for adding them on.
I think it likely to make sense to use one of the optional power feed wiring methods. And it almost certainly means using a later alternator.

Basic power circuits for 67 is explained in this post so read that first.
headlights not working
Thanks, guys this is all great information. I really appreciate the help!
 
I wouldn't run anything off the battery directly.
The ones that will be used when the engine is off, I might tie in with a terminal post.
The ones that will be used when the engine is running above idle speed, I might tie to the alternator output with a terminal post and/or additoinal fuse box.
You could use the empty accessory fuse slot in the existing fuse box - if the currents will not be too high.
There is only one slot there, so it can't be used for things that you wan to work with the key off, and also work with things that should work with the key on.
Each accessory should have the power it will need listed somewhere. It may be in Watts, it may be be in amps at 12 or some other voltage.
Get all that information and you can start planning a design for adding them on.
I think it likely to make sense to use one of the optional power feed wiring methods. And it almost certainly means using a later alternator.

Basic power circuits for 67 is explained in this post so read that first.
headlights not working
Thanks, guys this is all great information. I really appreciate the help!
 
If you study the factory wiring diagrams you'll be surprised to learn that many of the accessories this car came with are not fused, other than the fusible link outside the bulkhead. You have only 2 fuses hot at all times, 2 fuses that are hot in run, 1 for dash lights. Most of these are shared by multiple circuits, reverse lamps share radio fuse for example.
So if you parallel another electrical system for all these addons you will need a higher output charging system. That one charging system has capability to send more current through all the OEM wiring too. 60 to 80 amps could travel a wire, through a switch, designed/rated for 42 amps max. Look closely at its condition, consider upgrades. Good luck with it.
 
If you study the factory wiring diagrams you'll be surprised to learn that many of the accessories this car came with are not fused, other than the fusible link outside the bulkhead. You have only 2 fuses hot at all times, 2 fuses that are hot in run, 1 for dash lights. Most of these are shared by multiple circuits, reverse lamps share radio fuse for example.
So if you parallel another electrical system for all these addons you will need a higher output charging system. That one charging system has capability to send more current through all the OEM wiring too. 60 to 80 amps could travel a wire, through a switch, designed/rated for 42 amps max. Look closely at its condition, consider upgrades. Good luck with it.
besides the alternator, what would I need to upgrade? the wires? the bulkhead connector? I am new to electrical work; I just want it smooth and safe.
 
All of your accessories need to be set up so they are on an ignition run type circuit. You never want them run to a fuse block directly from the battery, that makes then "hot" all of the time. If the car is parked for a long period of time without a battery tender type charger, the accessories that have a background memory will slowly sap the battery. Even modern cars have that problem, a case in point is my Dodge Ram, if I don't run it for we'll say two weeks & don't keep a trickle charger on it the radio/clock memory will sap the battery to nothing.
 
Yes.
Once you understand what the factory did, then the best way to add each of the new accessories can be figured out.
There will be more than one way and advantages and disadvantages to each. It's easy to describe changes as 'upgrades', but they aren't always.
That's why I didn't provide a specific answer before or now. Then you're just doing what I suggest, which would be based on very limited info about your accessories and how you intend to use them.
 
There's a great example. Demon racer would put them all on switched for a reasons he explained. If I had power locks I'd probably want them on all the time. Power windows used to always be on switched but the last decade many vehicles come wired so they work without they key on. You know much better how you intend to use them than we do. With that info and how much power they take, its much easier to come up with a plan.
 
1...Upgrade factory wiring. At minimum, do some sort of upgrade to the main charging line, consider bypassing the ammeter.

2...For darn sure add a second fuse panel. Feed it completely separate with oversize wire

3...Add a minimum of 2 switched relays, 1 to power the existing ignition circuit under the hood "ignition run" and one to switch off the original accessory circuit. That relay can "key" the added stuff without loading the original

4...Think carefully about fuses. You want them to protect the WIRE and you want them as CLOSE to the source of power as possible.

5...For sure upgrade the alternator, see 1 above

6...I would ignore the statement "don't power direct off the battery." After upgrading the alternator and associated wiring the battery is EXACTLY where you want to source the power

When an alternator is PROPERLY wired, NOT like the original, that wiring is no longer an issue. But the battery acts in some ways like a filter and is much less "noisy" (RF/ EMI issues) than the alternator output.

Alternator output wiring, especially when adding "more stuff", pumps, fans, big stero, etc, needs to be OVER sized 60-80A? I'd run about no6 wire to battery. If you don't have / can't get some, parallel, 2 or more no 10 wires

Here's a MARINE amp/ capacity chart. Remember, the distance figure is "round trip" as in a wood/ glass boat no ground return. So the 10' distance example is same as 5' of wire in your auto

https://www.westmarine.com/WestAdvisor/Marine-Wire-Size-And-Ampacity

ampacity.jpg
 
Last edited:
Here's another example. Say you're planning on cranking 300 Watt stereo while tailgate bar-b-q at the local football stadium. That's different than playing a 100 Watt unit moderately while driving with the windows down.
 
67, our comment about powering off of the battery was meant as not powering any accessories directly off the battery.
 
There's a great example. Demon racer would put them all on switched for a reasons he explained. If I had power locks I'd probably want them on all the time. Power windows used to always be on switched but the last decade many vehicles come wired so they work without they key on. You know much better how you intend to use them than we do. With that info and how much power they take, its much easier to come up with a plan.
I see what you're saying; I appreciate it. Frankly I am not sure I would have considered it-so Thank you.
 
1...Upgrade factory wiring. At minimum, do some sort of upgrade to the main charging line, consider bypassing the ammeter.

2...For darn sure add a second fuse panel. Feed it completely separate with oversize wire

3...Add a minimum of 2 switched relays, 1 to power the existing ignition circuit under the hood "ignition run" and one to switch off the original accessory circuit. That relay can "key" the added stuff without loading the original

4...Think carefully about fuses. You want them to protect the WIRE and you want them as CLOSE to the source of power as possible.

5...For sure upgrade the alternator, see 1 above

6...I would ignore the statement "don't power direct off the battery." After upgrading the alternator and associated wiring the battery is EXACTLY where you want to source the power

When an alternator is PROPERLY wired, NOT like the original, that wiring is no longer an issue. But the battery acts in some ways like a filter and is much less "noisy" (RF/ EMI issues) than the alternator output.

Alternator output wiring, especially when adding "more stuff", pumps, fans, big stero, etc, needs to be OVER sized 60-80A? I'd run about no6 wire to battery. If you don't have / can't get some, parallel, 2 or more no 10 wires

Here's a MARINE amp/ capacity chart. Remember, the distance figure is "round trip" as in a wood/ glass boat no ground return. So the 10' distance example is same as 5' of wire in your auto

Marine Wire Size and Ampacity | West Marine

View attachment 1715520681
thank you this ls very helpful!
 
-
Back
Top