Bulkhead bypass vs ammeter bypass

[remytherat]

I would like to run a 90 amp alternator and I’m wondering whether I should just bypass the charge wires in the bulkhead or if I should bypass the ammeter entirely. Electrical draw will not be huge, just electronic ignition, headlights, electric fan

 

[RustyRatRod]

I would like to run a 90 amp alternator and I’m wondering whether I should just bypass the charge wires in the bulkhead or if I should bypass the ammeter entirely. Electrical draw will not be huge, just electronic ignition, headlights, electric fan

Opinions vary. Mine is, as long as the ammeter is working, the connections look good with no brown like they've gotten hot I'd leave the ammeter. Some say to do the whole shebang and eliminate it. I have my system completely factory intact on my 64 Valiant, because I don't intend on adding any heavy loads and everything works well.

 

[remytherat]

I’m rewiring the whole car because everything was trashed
The bulkhead connectors crumbled in my hands as I removed them and the wires were cracked and bare in some places.

I want the stock stuff to work, just want to protect the new harness however I can. Oh and I already have the higher current alt.

 

[dano]

Running a separate large charge wire (and mega fuse) from the alternator to the battery helps take the load off the bulkhead. Bypassing the Amp Meter prevents a potential issue at the Amp Meter itself. As stated, opinions vary, I'd prefer my 55 year old $30k+, blood, sweat, and tears investment not to burn my house down.

 

[RustyRatRod]

I’m rewiring the whole car because everything was trashed
The bulkhead connectors crumbled in my hands as I removed them and the wires were cracked and bare in some places.

I want the stock stuff to work, just want to protect the new harness however I can. Oh and I already have the higher current alt.

Well, if you're putting in a higher capacity alternator, I would go ahead and bypass the ammeter.

 

[Darter6]

I go both ways (No not like that...) If using a stock say 38 amp alt and not doing a complete re-wire
I tend to drill thru the bulk head connector(they have lots of empty spaces)then run a 10 gauge thru the hole to the ammeter. Doing anything more amps than a 72 amp then yes by pass the ammeter. We usually send the ammeter out and have it rewired for volts if doing a semi resto making it look stock to the rest of the gauges. My 2 cents.

 

[slantsixdan]

I would like to run a 90 amp alternator

Read this.

 

[RustyRatRod]

I would like to run a 90 amp alternator and I’m wondering whether I should just bypass the charge wires in the bulkhead or if I should bypass the ammeter entirely. Electrical draw will not be huge, just electronic ignition, headlights, electric fan

Why do you want to run such a high amp alternator? Are you adding electrical items?

 

[4spdragtop]

Follow slantsixdan's advice. He knows electrical. Everything I've read says to NOT over do the alt unless u need to. It will cause fires.

 

[memike]

Opinions vary. Mine is, as long as the ammeter is working, the connections look good with no brown like they've gotten hot I'd leave the ammeter. Some say to do the whole shebang and eliminate it. I have my system completely factory intact on my 64 Valiant, because I don't intend on adding any heavy loads and everything works well.

Same here broth, Victoria has grown and finding low amp alternators can be a pain, so before my sons claim it from my dead hands I better update it, keep up the music, I enjoy hearing you sing.

Read this.

Thank you Dan, you've helped me many times threw out my 66 build, this is the different routes to go.

 

[318willrun]

Some run a wire from the alternator to the starter relay battery post. Is this the same results basically, as running to the battery itself?? ??

 

[j_anderson]

I’m rewiring the whole car because everything was trashed
The bulkhead connectors crumbled in my hands as I removed them and the wires were cracked and bare in some places.

I want the stock stuff to work, just want to protect the new harness however I can. Oh and I already have the higher current alt.

I rebuilt almost every harness in my car except the main dash harness but mine was in good shape. I did check every wire in it.

When I rebuilt a harness, I sized up the wire 1 gage. The manual tells you which wires are which gage.

 

[remytherat]

Alright well it sounds like I will be fine to run the 90 amp if I add a large wire from the charge post on the alternator to the battery post on the starter solenoid or the positive battery post itself. My understanding is that it shunts current away from the firewall connectors.

 

[azaustin]

I tried the link to the slant six site on wiring a shunt but it didn’t work. A shunt seems like a viable alternative as long as you use the correct resistor in parallel with the meter. It would be nice to see how it was done. I’ve got two cars with ammeters and I’d like to keep them. They are nice if you understand what they are telling you, and if they are working correctly.

 

[67Dart273]

If you run an underhood bypass cable, fuse or breaker it. BUT THAT DOES NOT mean you don't have to fix the bulkhead, and then bolt the old ammeter wires together. the old big RED and BLACK still need good bulkhead terminals as then are not paralled infeeds into the pass compartment.

 

[318willrun]

Read this.

If you run an underhood bypass cable, fuse or breaker it. BUT THAT DOES NOT mean you don't have to fix the bulkhead, and then bolt the old ammeter wires together. the old big RED and BLACK still need good bulkhead terminals as then are not paralled infeeds into the pass compartment.

Some have run a wire from the alternator to the starter relay battery terminal. Is this the same results basically as running it to the battery itself?

 

[slantsixdan]

Some have run a wire from the alternator to the starter relay battery terminal. Is this the same results basically as running it to the battery itself?

It's basically widening and repaving the road from point A (alternator) more or less halfway to point B (battery), then just stopping and calling the job "done".

You're going to have wire and apropriate tools out, why not do the whole job properly?

 

[318willrun]

It's basically widening and repaving the road from point A (alternator) more or less halfway to point B (battery), then just stopping and calling the job "done".

You're going to have wire and apropriate tools out, why not do the whole job properly?

Thank you for answering

 

[DartGTDan]

I ran an additional 12ga wire from the alternator to the Battery + (protected with a 16ga fuse link). This provides a parallel path, taking 1/2 the "load" of off the original wire in the bulk head connector.

Because I've heard horror stories about some ammeters going up in flames I decided to bypass it. All I did was put both ring terminal lugs on one of the ammeter's studs. I removed the RED 12ga wire and put it onto the stud with the BLACK 12ga wire (that feeds the "welded splice").

 

[azaustin]

This has all been very interesting to me. I think we are giving Ohm’s Law some real exercise here. I’d really like to see some schematic drawings of some of these solutions to the Ammeter of Death problem (I know, I am inviting the FABO hate mail swarm of death here, but…). Also, the “type of conductor, length of conductor, and cross sectional area mantra” could have some impact here.

I’ve got my sword pointing upward and I’m leaning forward. Attack!

 

[BillGrissom]

The Magnum V-8 engines ran a thick wire (~8 awg) from the alternator output to BAT+, across the timing cover, so you could do that. I took that cable from a junkyard one (Grand Cherokee or Dodge truck) for my 1965. Mine doesn't run directly to BAT+, but near it. It runs to a back-back power diode on BAT+ which breaks down in forward bias ~0.7 V drop to shunt the alt current to BAT+ as the ammeter reaches its limit (around that voltage drop). I posted PN's and photos ~15 yrs ago.

 

[remytherat]

Thanks for the pointer, I have a magnum harness kicking around from my 5.9 swap.

So you’re basically running a zener that activates the shunt wire when the alt out is 0.7V greater than bat+?

 

[RLF Cuda]

If you want really good wires and terminals, BatteryCableUSA has what you need. Quality Copper Battery Cables Made in the USA! - BatteryCablesUSA
The battery terminals are first rate. I used the military grade terminals with side studs for connecting wires. The restoration shop built power and ground wires for a 80A alternator. The alternator power does run partly through the firewall so the ammeter shows some charging, but the bulk of the power runs through a 10Gauge wire with fusible link directly to the battery. Other than the cheap Chinese alternator from O'Reilly which I want to replace, all works well.

 

[BillGrissom]

Thanks for the pointer, I have a magnum harness kicking around from my 5.9 swap.

So you’re basically running a zener that activates the shunt wire when the alt out is 0.7V greater than bat+?

Not a zener. I forgot if silicon or germanium. The diode is forward-biased, in both directions (2 in parallel). It always conducts forward, just very little current until >0.5 V drop, then current increases exponentially with voltage drop. I tested that keeps the dash ammeter from pegging, perhaps tops out ~3/4 scale with a squareback alternator on full-field. Fine for me since I just care to see its charging after starting the car.

I recall ~200A rating (depends on heat-sink). Bolt terminals. Actually dual diodes in the package on an aluminum base. I cut in two, flipped one around, and bolted together to realize parallel diodes. Posted PN in the past w/ photos. You'll have to search. Few people here could understand or follow. One guy bulked up my post arguing (with an engineer) about current and voltage that he didn't understand.

 

[360notch]

Running a separate large charge wire (and mega fuse) from the alternator to the battery helps take the load off the bulkhead. Bypassing the Amp Meter prevents a potential issue at the Amp Meter itself. As stated, opinions vary, I'd prefer my 55 year old $30k+, blood, sweat, and tears investment not to burn my house down.

Could not agree more. Even a reman stock alternator will increase the alternator output from the stock 35 amps to 55 amps or more, which will increase the battery charging current and thus increase the heat in the bulkhead contacts, even without any additional loads. Heat is proportional to the square of the current.

A volt meter will show you when the voltage is high enough to charge the battery, so you can tell if the charging system is bad. If you want a nice looking voltmeter, Mr. Heaterox was doing ammeter to voltmerter conversions for ralley dashes. Mr. Heaterbox is a class act, honest, good turnaround time, reasonable price, and stands behind his stuff.