Underhood Ammeter Bypass

3175375

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I used some remotely resettable circuit breakers in some test equipment that we used in a testbed. The mission crew operated them and the air crew didn’t have access to them and they were not part of the flight systems. They worked great and once we got everything worked out, we never had to reset them.
 

James Romano

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I used some remotely resettable circuit breakers in some test equipment that we used in a testbed. The mission crew operated them and the air crew didn’t have access to them and they were not part of the flight systems. They worked great and once we got everything worked out, we never had to reset them.

ahhh... My aviation brother... speakin' my language! HAHAHA!

I was going to mention Flight vs Maintenance C/B's... but I thought best not to bore the piss out of everyone. LOL.
 

3175375

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ahhh... My aviation brother... speakin' my language! HAHAHA!

I was going to mention Flight vs Maintenance C/B's... but I thought best not to bore the piss out of everyone. LOL.
Ha
We modified the power distribution system to isolate one engines generators for our ‘experiment’. The flight engineer ‘gave us the generator’ and we then could power up the system under test.
All of the instrumentation operated via 60 Hz converters that we spec’d out.
Upon the completion of our tests, we shut down the system under test and ‘gave back’ the generator and the flight engineer re-paralleled the generator back onto the aircraft bus.
I learned a lot about control systems in these activities that spanned most of my 32+ year career...
 

James Romano

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By the sounds of it, you were on either an L-1011, 707, 727, DC-10, DC-8 or 747. Minimum 3 engines for that experiment.
 

saylor

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wait you said it yourself - "reset it"
so it breaks and requires manual intervention.

so OK dont use a auto-resetting circuit breaker.

what if the circuit breaker melts its contacts?

you know what you do it your way ill stick with my fuses.
 

3175375

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By the sounds of it, you were on either an L-1011, 707, 727, DC-10, DC-8 or 747. Minimum 3 engines for that experiment.
A-3s first
DC-10 second - used the APU for the experiment - limited to 25k feet as the APU flamed out at higher altitudes
727 - this one we did the isolation on. APU wouldn’t operate airborne as the exhaust was over the port wing root. The 727 is still flying...
 

James Romano

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A-3s first
DC-10 second - used the APU for the experiment - limited to 25k feet as the APU flamed out at higher altitudes
727 - this one we did the isolation on. APU wouldn’t operate airborne as the exhaust was over the port wing root. The 727 is still flying...
Just about everything Boeing built is made to last.

We said good-bye to our last 747-400s. It was tough man. The Queen of the Skies. Damn good airplane. Fuselage will live on in the -800, but mostly as long haul cargo
 

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I did it similar but used 0/1 AWG from alternator to battery. I also run a 95AMP. Also ran same AWG to the starter and replaced the engine ground with it too. Voltage drops gone and it cranks way faster too. Just an Idea. 12 or 10ga seems pretty thin... I also have a 150amp fuse between the alt and battery.
 

James Romano

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I did it similar but used 0/1 AWG from alternator to battery. I also run a 95AMP. Also ran same AWG to the starter and replaced the engine ground with it too. Voltage drops gone and it cranks way faster too. Just an Idea. 12 or 10ga seems pretty thin... I also have a 150amp fuse between the alt and battery.

I can see the logic behind why you did this. By laws of current it makes perfect sense to drop the wire resistance as low as possible to get the most out of the AMP flow to do work (that's why the starter cranks faster). But I will say this... you've now removed the component's "built-in" resistance expectations of the wire's design. Meaning... they are being hit a lot harder than they were designed for. There is a reason why 10/12 AWG is used in these circuits, and not 0/1 out of the factory....cost AND design. Current flow meets wire resistance and is designed to. Adding in a 150 amp fuse now locks in your components to fail before the rating of the fuse is hit. 150 amp is massive for a car. If you're running a 95 amp alternator, you're well out of range of the Alternator using a fuse that size. The wire and fuse are now stronger than the components in the system.

Your weak spots are now your components, first one being the firewall connector, and then the starter relay.

Time will tell if this was a good design. But I would definitely carry a fire extinguisher at arms length. You see this a lot with houses.. yeah, you can pull out that 100amp panel and install a nice 250 Amp main then load up your panel with a ton more breakers... but did you upgrade the drop from the outside to the panel? If not... the thick 100 amp rated cable running from your street connection to your meter is now your main breaker to your house.... not the one in the panel.

I'm sorry, I'm not trying to sink you're boat.
 

cbarge

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^^^^^^This^^^^^
What James said..
The goal in this thread is protect the components --not set them up for failure.
 
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Big_John

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The goal in this thread is protect the components not set them up for failure.

You know... Second time I've seen this.

There seems to be a real misunderstanding about fuses and fusible links. It's a penny in the fuse box where the wires and components are gonna fry well before the fuses ever blow. Hopefully, @James Romano 's explanation will sink in. The one I tried to explain fell on very deaf ears.

Any fire will all get blamed on the ammeter anyway no matter what is done along with kidnapping the Lindberg baby.
 

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At the relay use a fusible link. I used an 18 gauge with my 12 gauge wire.
Fury only has a 38 amp alternator.
On my other car,I am running a 78 amp alternator and used 10 gauge wire with a 14 gauge fusible link.

Hi CBARGE,
Is 18 awg fusible link the best size to protect a 12 awg circuit? Just curious, I've read that you go 4 sizes smaller than the wire size of the circuit you're protecting. Too, did you use an 18 awg female connector with a 12 awg male (or visa versa) or can you just use 12 awg connectors for both? I'm installing a new fusible link on my car too but am not familiar with connecting two different wire sizes. Thanks.
 

cbarge

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Hi CBARGE,
Is 18 awg fusible link the best size to protect a 12 awg circuit? Just curious, I've read that you go 4 sizes smaller than the wire size of the circuit you're protecting. Too, did you use an 18 awg female connector with a 12 awg male (or visa versa) or can you just use 12 awg connectors for both? I'm installing a new fusible link on my car too but am not familiar with connecting two different wire sizes. Thanks.
4 sizes is the norm.
As I mentioned it varies on the output of the alternator. The bigger alternator bigger wire.
You can use red or blue female butt connectors but as I demonstrated I used male and female connectors that are proper size to the wire. I did that for future road side repairs if needed.

Ultimately it is best to solder the link and wires together and use shrink tubing.
 

Rosco

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4 sizes is the norm.
As I mentioned it varies on the output of the alternator. The bigger alternator bigger wire.
You can use red or blue female butt connectors but as I demonstrated I used male and female connectors that are proper size to the wire. I did that for future road side repairs if needed.

Ultimately it is best to solder the link and wires together and use shrink tubing.

OucH! I heard no solder. Changes resistance...
I like the idea of solder on all the crimp connectors as well as heat shrink tape but thought that was a no no on the link connectors.
 

cbarge

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OucH! I heard no solder. Changes resistance...
I like the idea of solder on all the crimp connectors as well as heat shrink tape but thought that was a no no on the link connectors.
I guess it is a matter of personal preference.
Some I did solder if the car lives in either high humidity climates or winter driven being exposed to corrosive/damp environments.
Majority of the ones I had done not winter driven and used appropiately sized connectors.
 

Rosco

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I guess it is a matter of personal preference.
Some I did solder if the car lives in either high humidity climates or winter driven being exposed to corrosive/damp environments.
Majority of the ones I had done not winter driven and used appropiately sized connectors.

I guess after further reading, sounds like if your solder doesn't wick up into the insulation you're ok. Sounds like you're expected to do it right!!
I think using an uninsulated crimp connector and solder would make a great connection. Just can't be a bozo about the solder joint and feed 6 inches of solder into the wire. A little dab 'll do ya.
I've got a bit of a mess from my battery being hooked up backasswards. I haven't jumped into the electrical repairs but have a feeling I will get a lot of practice making new connections. We'll see. Thanks for your post.
 
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I will report back to this thread, whether my standard OTP fuse blows due to high charging current spikes or not. If so, I will replace with a 14 or 12 awg fusible link. It will be no earlier than March, when the driving season starts over here in the rust belt of Europe.

So I was advised earlier in this thread, that the 30amp OTP fuse I had used would probably blow due to high currents right after starting. And you were right; it did blow. Twice. I never managed to measure more than 18A in the bypass cable with my amp clamp, but it must have been more than 30 in some occasions.

I sourced a 14gauge fusible link and replaced the fuse with that.
 
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Is this bypass truly all it takes to make the car safe from electrical fires caused by ammeter or bulkhead connection failure... one wire from the alternator to the starter relay? For some reason, I thought this was much more complicated than that...

-Gregg B.


It took longer to do the thread compared to the wiring,LOL!!
But I cannot stress enough how important this 15 minute job is .
What it does is piggy back on the ammeter circuit. This wire takes 50% of the load away from the ammeter itself.
We all know the ammeter gauge is the achilles heel in our beloved old Mopars.
The fusible link is a safeguard should the alternator short out and not burn the dash or car to the ground.

You wil notice that the ammeter gauge will not swing as crazy as before and will not read 100% accurately.
But still works--until is does short out but the car will still function normally on a day to day basis.
An option is install an afermarket volt gauge.
Simpy hook it to a switched 12 volt source and ground it to body. done.

In laymans terms the Red wire at starter relay goes through the bulkhead and eventually to the ammeter gauge--which is hot all the time.
Hot I mean live as in anything that is run by battery no ignition key needed (headlights,hazards,dome light lighter,etc)
The black wire on the ammeter goes to the ignition switch which as you know powers anything that needs the key on.
So when the ammeter shorts out you have NOTHING!
This simple little addition is worth its time,trust me.

I cannot take credit for this mod.I first read about it in MOPAR ACTION
20 years ago writen by Richard Ehrenberg.
Hope this helps.
 
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I have a brand new 90 amp alternator I was given to me, and I intend to install this on my '68 Imperial. What gauge wire and fusible link should be used with this set-up?

-Gregg B.


At the relay use a fusible link. I used an 18 gauge with my 12 gauge wire.
Fury only has a 38 amp alternator.
On my other car,I am running a 78 amp alternator and used 10 gauge wire with a 14 gauge fusible link.
View attachment 378438
 
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