# Upgrading Old Fuse Box

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#### AaronsCars

##### New Member
Hi guys, I am looking for some electrical help on how to add a secondary fusebox to my car. I have a 1989 Maserati 430, these era cars came out of the factory with underpowered fuseboxes prone to over heating. Well, my box was toast when I bought the car and now that ive had the car a few months it has really quit and its time to make some changes.
My radiator fans and lights came on together, AC control unit had no power, dome lights had no power, horn lost power, mirrors had no power, the list goes on. I removed my old fuse box and I have some crunchy crusty circuits, its beyond my repair. I have a refurbished, tested box on the way. But I want to add a secondary fusebox to my car to separate the circuits.
According to my research, the AC, the window defrost, and the heat are what can cause the fusebox to over heat and melt the solder joints. I would like to get my AC/Heat, cig lighter, rear window defrost, and horn into its own box. Maybe even some more items depending on how difficult of a job it is.

There is a basic kit that I can get through a website called MIE that supplies all the old parts for these cars, but its just two relays that move the AC circuits out of the fusebox to an independent system. The kit is $135, but I know I could make it for much cheaper. Its two service relays, each with a fuse, and then the appropriate wiring. Personally I would think for around$135 I could install an entirely new secondary fuse box that contains more than just the AC circuits.

Thoughts and opinions?
I have the factory manual for the car, so I have the (crappy) wiring diagrams. I also have pictures of the fuse box.

I am not an electrical genius by any stretch. I know most of the basics. I know generally how wiring works, but in this situation I would like to have some expert input. Especially because replacement parts for some of the oddball electrical items can be a bit tricky to come by or extra .

#### dr pepper

##### Well-Known Member
Nice motor.
AC clutches usally only take about an amp or so, is yours motor driven or engine driven.
If you want to keep the original fuse type then you'd probably have to get one of the original type fuse boxes (ceramic fuses?), if not you could go to a auto electrical supplier & get a universal Ato or mini Ato style fusebox with 1/4 terms each end, and then for the relays you can get standard 3/4" box type relays with a tab on you can bolt to a bracket of your own, and then make out all the connections.
If you have trouble finding stuff try a chandlers, you can get all kinds of auto electical stuff for boats.

#### AaronsCars

##### New Member
My AC is belt driven by the engine, currently the AC is out and in need of repair so it will not be drawing any current. But this too will be fixed in the future.

I have no need for the original fuses LOL, it uses the old style bullet fuses.

I found a nice box on amazon for \$31 that I liked, its a smidge bigger than I was hoping for but I think it'll manage fine. It'll just take some creativity, like the rest of this car LOL. Its an IROCH Fuse box rated for 100amps, 12 way with negative bus.

My plan is to get the simple things onto this panel. Cig lighter, dome lights, and clock for sure.
In the future when I put in a new radio I will probably wire in the new one and wire it to this box, and leave the old wiring harness intact to the old box. I do not plan on going OEM with the radio.

Both boxes should be here friday, if all goes to plan I should have some things to work on this weekend.

#### AaronsCars

##### New Member
I’ve got the new fuse box started. I have it in the car, grounded to the ground bolt/body in the engine bay.
I have the sunroof grounded and the main fuse box grounded through this one. I found the main fuse box ground and it’s original grounding post on the car is corroded, thought better to just move it entirely.
Next I’m wiring the cig lighter and Ac Control box.

I haven’t added any power to the new box though. I have some questions.
I have never wired a relay. Is it safe to wire just one relay for the accessory fuse block?
I’m using this block so that it doesn’t get hot until after the key is turned. Would I wire it-battery>circuit breaker>relay>fuseblock?
How do I choose what size circuit breaker?
I do plan on putting the cars audio system on this block eventually.
Is 1 relay okay for switching the fuse box on after the key is turned?

#### Externet

##### Well-Known Member
I would get at the boneyard a healthy fuse box with intact good lengths of wire harness, relays and everything from a modern Gm, Toyota.... vehicle that fits your available room and junk the originality.
Perhaps with some adrenaline, transplant the troubled wiring from a similar featured vehicle. They all have the same devices to run at nearly same locations; but you must know how to read schematics from yours and the donor. Solder all splices and shrink tube them. If computerized controls are implemented, it may be over your skills.
Done that to four vehicles.

#### AaronsCars

##### New Member
That would be a terrible hassle on a car like this, apples for oranges.
The wiring on my car is fairly simple, the fuel injection and the turbo control are the only computers on the car. The rest of it is 12v+, ground, switches, and relays.
The fuseboxes were a known weak point but they weren't bad enough to remanufacture the whole system, or at least I have never heard of anyone doing such. Im just moving some accessories and the AC off the main block, items that come on after the key has been turned.

#### gophert

##### Well-Known Member
That would be a terrible hassle on a car like this, apples for oranges.
The wiring on my car is fairly simple, the fuel injection and the turbo control are the only computers on the car. The rest of it is 12v+, ground, switches, and relays.
The fuseboxes were a known weak point but they weren't bad enough to remanufacture the whole system, or at least I have never heard of anyone doing such. Im just moving some accessories and the AC off the main block, items that come on after the key has been turned.
I doubt solder is melting. These wires are usually crimped to spade connectors. Solder creates a brittle connection that can break due to strain/stress movements. I recommend crimping - make sure you buy Automotive grade wire (insulation is the key).

#### AaronsCars

##### New Member
Here’s the fuse box when I pulled it out of the car. It’s since been replaced with one that isn’t broken.

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#### gophert

##### Well-Known Member
Here’s the fuse box when I pulled it out of the car. It’s since been replaced with one that isn’t broken.
My fault. I was thinking about reliable automotive technology and completely forgot that the joy of Italian Design comes with the joy of Italian engineering.

#### AaronsCars

##### New Member
Lol yea! That’s the problem haha, it’s italian....it’s not under the normal electrical category...The Italians did weird things. The problem from what I have seen is that they over simplified it, and put too much faith in single circuits, then overload

#### dr pepper

##### Well-Known Member
The coil side of the relay is tha control side, and the contact side the load side.
I'd probably fuse or 'breaker the control side and load side seperately.
The control sides could be commoned to one breaker, except for critical ones such as engine/headlights.

#### AaronsCars

##### New Member
I won’t be messing with the headlights I don’t think. So those won’t be an issue.
So one breaker on the control side? Battery side or fuse box side?
How do I decide which size breaker?

#### dr pepper

##### Well-Known Member
Put the breaker close to the battery, with as heavy a cable as will fit.
The breaker rating wants to be a bit higher than the max perceived load, not necessarily all the loads combined, just the highest likely.
Supposing you have 5 relays than a 6 amp breaker ought to do.

#### KeepItSimpleStupid

##### Well-Known Member
A few things that might be useful. The newer cars are distributing power. In 1982, there was a block in the engine compartment. This particular vehicle had blade fuses for each low and high beam. I had a 1965 vehicle that put the headlights on a breaker that was part of the headlamp switch, One night my headlights had a 30s on and 30s off pattern, One of the headlamps developed a shorted filament,
So, this is a case where the headlamps draw a fair amount of power, so the box was placed in the engine compartment along with rellays to switch on the headlights.

Be careful with the ACC block. It normally goes dead when the the starter is engaged. The bower motor and radio die during start.

Incadesent lamps might draw about 10x more of the steady state current when cold, so it doesn't make sense to turn the lights off automatically with starter engagement.

Headlamps and exterior lighting are wired to BATT.

4-way flashers work all the time, but turn signals don't. They would be partially wired to the IGN block. That block would get the spark plug system.

The alternator generally gets a "fuseable link" and not a fuse. A fuseable link is a section of wire that would melt, The 1982 vehicle had wires in the engine bay fuse block.

There is some wackyness in how the alternator is wired so that there is no phantom load from the regulator when the car is off.

#### shortbus=

##### Well-Known Member
The alternator generally gets a "fuseable link" and not a fuse.
What make car is that? Any car I've worked on the fusible links are on the distribution side of the power not the charging side.

#### dr pepper

##### Well-Known Member
Yup me too.
I noticed later hondas have a data pid for the current in and out of the battery so they must have a shunt too.

#### AaronsCars

##### New Member
Ok, what I’m doing is a simple system I’m not redoing the whole deal.
All my plan is to move the hot wire from a handful of instruments to the accessory box, so they draw their 12V from box 2 instead.
Is it possible for me to use 1 relay for the whole fuse box, as in wire the battery to the circuit breaker, then circuit break to relay, relay to fuse box. So that when the key is turned it powers on the fuse box?
Because I’m not putting anything on the box that will be used when the car is off.

#### shortbus=

##### Well-Known Member
I don't understand the need for a relay or circuit breaker myself. I've never worked with an Italian car though. But in many of the old cars I've "hot rodded" I added an extra fuse block, I just tie into the existing battery feed on the old, original block.

#### AaronsCars

##### New Member
I don’t want the circuits drawing electricity all of the time. It doesn’t have a large battery or large alternator for one.
Plus in any standard auto fuse box, only certain circuits stay hot when the car is switched off. The rest are activated by the ignition switch

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