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Old 05-09-2020, 08:56 PM   #1
Mini-Skoolie
 
Join Date: Jul 2019
Location: Asheville, NC
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Year: 1988
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12v Terminal Block Mayhem !

Hey all, got a little issue with my 12v terminal block/main 12v panel. The terminal is split into two parts, and only about half of the R side has power. (Tested with multimeter)

The positive terminals are the slide-on connectors with the orange wires behind the blocks themselves, the negatives are the screw on ring terminal connectors.

I’ve got barely enough terminals to power all existing accessories as it is.

Buuuut the issue here is that I’m trying to wire up 3 new things (radio head unit, 12v phone charger, and driver fan. Trying to figure out the smart move.

There are only two available positive ports. Most of the negative are already doubled up as you can see in the photos. Is there a big issue with hooking up multiple things to the same positive port given the connections are solid? It’s all just 12v right?

I was thinking maybe I could just solder two positive things to one terminal or use a 3 way y-connector to connect two things to one port. Any big issues with doing that and calling it a day?

Or should I try and dig into the wiring abut and try to fix the terminal block, or possibly even wire a new one?

All input is much appreciated. Feeling a little stalled out on this one!
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Old 05-09-2020, 09:41 PM   #2
Traveling
 
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I previously replied thinking you had a broken wiring block. Yes, you can piggyback multiple low load circuits off of a common feed, but it is not recommended as overloading can result in overheating and a fire. My advice is to wire a simple fused 12V relay direct to the battery, creating your own auxiliary circuit. You can then wire the trigger for the relay to be switched by any circuit you wish, including the ignition feed.

Switched 12V Relay Schematic.JPG
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Old 05-09-2020, 09:49 PM   #3
Bus Crazy
 
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What about adding another terminal block off the primary?
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Old 05-09-2020, 10:00 PM   #4
Traveling
 
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Quote:
Originally Posted by Danjo View Post
What about adding another terminal block off the primary?
Still risky, as you are increasing the load on already ancient wiring.

Don't Be *THIS* Guy

I attached a schematic of an appropriate relay and how to wire it up to me previous post. Older style GM relays from 1994 and older will have larger terminals and will be able to handle heavier loads. They are usually rated for about 20 amp if memory serves. You can get these things out of a salvaged car at the boneyard for probably five or ten bucks and get about 8 to 10 in of the wiring harness with it to help in installing. GM used these exclusively for many late model vehicles, fuel pump is a common utilization.
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Old 05-09-2020, 10:27 PM   #5
Bus Crazy
 
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Quote:
Originally Posted by CHEESE_WAGON View Post
Still risky, as you are increasing the load on already ancient wiring.

Don't Be *THIS* Guy

I attached a schematic of an appropriate relay and how to wire it up to me previous post. Older style GM relays from 1994 and older will have larger terminals and will be able to handle heavier loads. They are usually rated for about 20 amp if memory serves. You can get these things out of a salvaged car at the boneyard for probably five or ten bucks and get about 8 to 10 in of the wiring harness with it to help in installing. GM used these exclusively for many late model vehicles, fuel pump is a common utilization.
I meant off the battery post with a new primary to a new fuse block. Wouldn’t that be like having a “new” setup?
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Old 05-09-2020, 10:28 PM   #6
Bus Crazy
 
Join Date: Sep 2018
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Quote:
Originally Posted by CHEESE_WAGON View Post
Still risky, as you are increasing the load on already ancient wiring.

Don't Be *THIS* Guy

I attached a schematic of an appropriate relay and how to wire it up to me previous post. Older style GM relays from 1994 and older will have larger terminals and will be able to handle heavier loads. They are usually rated for about 20 amp if memory serves. You can get these things out of a salvaged car at the boneyard for probably five or ten bucks and get about 8 to 10 in of the wiring harness with it to help in installing. GM used these exclusively for many late model vehicles, fuel pump is a common utilization.
What would you use for the trigger?
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Old 05-09-2020, 10:29 PM   #7
Skoolie
 
Join Date: Jul 2015
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Engine: Ford 7.3 Powerstroke
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is this a full sized bus?

Quote:
Originally Posted by silvermachine View Post
only about half of the R side has power. (Tested with multimeter)

I’ve got barely enough terminals to power all existing accessories as it is.
if they filled up all the terminals from the factory, I'd be worried that they overloaded the boards somehow. the problem could be as simple as popped fuses, but if not you can usually figure out the problem with that multimeter (the ohmmeter is used a lot for this sort of thing in my shop). corroded grounds is a common one that can cause all kinds of problems.

Quote:
Originally Posted by silvermachine View Post
Buuuut the issue here is that I’m trying to wire up 3 new things (radio head unit, 12v phone charger, and driver fan. Trying to figure out the smart move.

There are only two available positive ports. Most of the negative are already doubled up as you can see in the photos. Is there a big issue with hooking up multiple things to the same positive port given the connections are solid? It’s all just 12v right?
voltage isn't everything. both the fan and the charger take minimal power (amps). a 6" fan draws less than 2 amps, and the charger is 2 amps (although it may be 2 amps per usb slot). there isn't much risk of overloading a circuit with current draw like that, and it sounds like you have two available inputs, anyway.

a typical head unit takes more like 5 amps (check the owner's manual), and with something like that, I'd want to wire directly to the fuse block, with a dedicated fuse.

Quote:
Originally Posted by silvermachine View Post
Or should I try and dig into the wiring abut and try to fix the terminal block, or possibly even wire a new one?
so often this kind of thing is something simple, but it can take FOREVER to track it down. it's really up to you whether you want to get into it. I can tell you that a new system isn't easy either, not even a prefabricated one like CHEESE_WAGON mentioned.

my suggestion would be to get it fixed one way or another. at least figure out which circuits aren't working, and what they do. that way you can make a more informed decision about how necessary they are.

with my bus, I found I was able to rip almost all the wiring out of the original DC distribution panel after I'd traced all the wires. I also installed 4AWG positive and negative cables (with a big ol' inline DC breaker) directly from my batteries. at that point I didn't have to worry about how much power I was drawing, and I had plenty of unused inputs.

this might fix your problems, too.
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Old 05-09-2020, 10:33 PM   #8
Skoolie
 
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wow. you guys move quicker than me haha.
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