MAD Bypass Alteration - Risk?

[jrcr_15]

Concerns on this wiring?

I am installing a higher amp alternator to handle the accessories on my car: Dual cooling fans, electric water pump, MSD, Fitech, Snow Water meth injection etc.

My ammeter is already removed and a voltmeter added in its place. Thoughts on this modification. Based off the MAD design.

Essentially:
I am going to add a fuse block between the alternator and starter relay. Then run a wire from the SR into another fuse block, bypass the bulkhead altogether and feed the accessories .

My thoughts are this would be safer as opposed to running more amps though a bulkhead connector.

Additionally, I have a new wiring harness and will be installing a new fuse block too, my wiring will be in tip top condition.

Any foreseeable risks? I believe I have it all covered, but I am no electrical expert by any stretch.

 

[1969383S]

Smart thing to do for your instance! Not for all though!JMO

 

[67Dart273]

The way you show your voltmeter, it is powered at all times. It will draw enough that when parked for awhile, it will eventually run down the battery. Run it through the key

Why did you do away with the alternator black. If you simply bypass the ammeter, then run a large gauge FUSED (or breaker) wire direct from alternator to battery, the black and red through the bulhead then work together to feed power into the pass. bay. This adds "more wire" size and is not a bad thing.

I believe "Crackedback" on here sells those bypass wires.

 

[jrcr_15]

The way you show your voltmeter, it is powered at all times. It will draw enough that when parked for awhile, it will eventually run down the battery. Run it through the key

Why did you do away with the alternator black. If you simply bypass the ammeter, then run a large gauge FUSED (or breaker) wire direct from alternator to battery, the black and red through the bulhead then work together to feed power into the pass. bay. This adds "more wire" size and is not a bad thing.

I believe "Crackedback" on here sells those bypass wires.

Thank you for the info! In terms of the wire going into the interior, it is a larger gauge, so I think it should be plenty..? Really taking a less is more approach.. if that makes sense.

 

[Mattax]

Less is not more in this case.
How the feeds are routed should depend on where the power is going.
Except during start, the power source is the alternator.
Except for when the battery needs recharging, the most direct connection to the items needing power is by feeding the main splice.
(obviously if other electrical equipment has been added or feed routing been modified then this may not be so. so lets look at your case and see how it applies)

I am going to add a fuse block between the alternator and starter relay. Then run a wire from the SR into another fuse block, bypass the bulkhead altogether and feed the accessories .

My thoughts are this would be safer as opposed to running more amps though a bulkhead connector.

Absolutely better to power your new equipment from an auxilery fuse box in the engine compartment.

I don't see any advantage of running two feeds from battery to the new fuse box.
The disadvantage is each additional connection is a potential for resistance.
Also as a practical matter, is it possible to get maxi fuses in the same box as regular fuses?

 

[Mattax]

These are the two wiring suggestions from 67dart273

The disadvantage to the way I drew this is if there is a ground short inside the car, there are two paths for the battery to discharge.

Connecting all of the new items to power using an additional engine bay fuse box makes sense. I'd also power the headlights from there and have everything setup on relays. The MSD should not need a relay as they basically have one built in.

Size the maxi fuses that are equivalent to the fusible link size for the wires downstream of the battery. That's the main job of the fusible link - to break the wire in safe way when there is a short to ground. The unprotected factory wires inside are mostly 12 ga (sometimes larger but protection is always based on the smallest wire or weakest connection) so those need equiv of a 16 ga fusible link.

Its worth looking at some of the fleet and similar wiring schemes the factory used to see how they sized and placed the fusible links.

 

[burdar]

Why did you do away with the alternator black. If you simply bypass the ammeter, then run a large gauge FUSED (or breaker) wire direct from alternator to battery, the black and red through the bulhead then work together to feed power into the pass. bay. This adds "more wire" size and is not a bad thing.

This is what I did. The wire coming off the alternator is already in the harness so it would have been more work to remove it. I just left it there. Now the interior is feeding from two locations instead of one. I did add a fusible link to the original black wire coming off the alt. Now both interior feeds have fusible links on them.

The bypass wire from the alt stud to the battery/starter relay has a very low chance of shorting to ground but I wanted to add some protection if the alternator shorted to ground internally. I added a fuse holder in that line before it connects to the relay. I also have a short piece of wire running from the relay to a buss bar under the battery tray. The buss bar powers the headlights and convertible top pump.

 

[Lord Sparky]

Crackedback headlight relay harness and charge wire from alt to starter relay.

 

[ir3333]

i just ran an 8 gauge wire from the alternator to the starter relay through a fuseable link and kept my
alternator and bulk head wiring stock which lets me see charging current.
Keep your bulkhead wires and connections clean and covered with dielectric grease.
I really like my system but i didn't load it up with many accessories.