Volt gauge wires

[Ethan]

I am putting new connections on at the bulkhead inside and under the hood along with the blocks. I got the inside done and installed auto meter oil pressure, water temp, and volt gauge. My question is can i leave the factor AMP gauge unhooked at the bulkhead sense i got the autometer volt gauge or does that wire power something else under the dash? Trying to eliminate that fire hazard if I can.

 

[Badvert65]

Two questions. First, are you installing VOLT or AMP gauges. There is a HUGE difference as to how they are connected, which leads to the second question.
The factory gauge should be an AMP gauge and not a VOLT gauge, so how are you bypassing, or replacing that gauge?

 

[MoparLeo]

Just curious. What exactly are we working on ? year/model ?

 

[Ethan]

1970 roadrunner with rally dash

Sorry after reading my post I had them flipped around. I installed autometer gauges. (Oil pressure, water temp, and volts) so can I leave factory Amp gauge disconnected at bulkhead connector under hood (pictured in first post) or does that negative and positive provide power/ground elsewhere? Sorry for the confusion

 

[Ethan]

Fixed the Original post to make sense as well. My bad

 

[Badvert65]

Ammeters are connected to electrical circuits in a specific way. The thing you need to do is connect the bulkhead connector just like the factory did. Then, on the dash, go to the rear side of the gauge panel and locate the ammeter connection. (do this with the battery DISCONNECTED). You will see that the ammeter has two studs with thick wires bolted to them. What you need to do is remove one of the leads and bolt it to the same stud as the other lead. Essentially bolting the wires together with the other stud not connected to anything. This will safely bypass the ammeter and require no hacking or splicing of the harness. I have done this to each and every Mopar I have ever owned. I have never had an issue ever. I am not a fan of ammeters in cars as most people don't know what to do with the limited information you can get from them. You get so much more practical information from a voltmeter and if a voltmeter fails, you won't be left dead in the road.

 

[Nacho-RT74]

 

[Ethan]

Ammeters are connected to electrical circuits in a specific way. The thing you need to do is connect the bulkhead connector just like the factory did. Then, on the dash, go to the rear side of the gauge panel and locate the ammeter connection. (do this with the battery DISCONNECTED). You will see that the ammeter has two studs with thick wires bolted to them. What you need to do is remove one of the leads and bolt it to the same stud as the other lead. Essentially bolting the wires together with the other stud not connected to anything. This will safely bypass the ammeter and require no hacking or splicing of the harness. I have done this to each and every Mopar I have ever owned. I have never had an issue ever. I am not a fan of ammeters in cars as most people don't know what to do with the limited information you can get from them. You get so much more practical information from a voltmeter and if a voltmeter fails, you won't be left dead in the road.

Iv had the dash apart multiple times and there is a 10-12 gauge black wire (negative) and a red wire the same size (positive). what are you exactly saying to do with those?. Just unhook one and tape it off?

 

[Badvert65]

On the back of a factory ammeter, there are two separate wires that bolt onto the ammeter terminals. Ammeters do not have a "positive" and a "ground". They have a "positive-in" and a "positive-out". Note: this is a very basic description of ammeter connections, I could get more technical but it isn't really necessary here.
Back on subject, the thing to do is to connect the 'positive-in' and 'positive-out' connections together. YES, bolt both leads to the same ammeter post and leave the other post 'empty. You have to connect them together to complete the circuit and bypass the ammeter, if you do not connect them together, you will have no electrical power to the rest of the vehicle. So, to recap, the ammeter has two leads, each bolted to a separate stud. Take one lead and put it together with the other lead on the same stud. This bypasses the factory ammeter, without any cutting or splicing of wires. This ONLY works with ammeters. You would NOT do this with a volt meter. It's late, but I can post pictures later.

 

[Nacho-RT74]

I am not a fan of ammeters in cars as most people don't know what to do with the limited information you can get from them. You get so much more practical information from a voltmeter and if a voltmeter fails, you won't be left dead in the road.

Limited information from ammeter? Woah! I get more and faster info from it than from a voltmeter!

I’m not saying the voltmeter doesn’t work, but Voltmeter is a referential reading while ammeter is a straight reading of the charge status!

Charge is load, and load is amperes while you can get high voltage but poor load.

Once got a short into the alt ( some rotor vent vanes getting friction with diodes bank while spinning ), ammeter was showing discharge while a multitester was showing me 18-20 volts at batt ( up to 24 reving up the engine ). Disconnected batt and engine stalled. What reading was the real one affecting the charge status? If I had voltmeter could think on overcharge status, not discharge, so the ammeter was the more realistic.

 

[Nacho-RT74]

On a side note, if you get a shunted ammeter system, you can get a damaged ammeter and everything still working. Shame this system was installed on Mopars since 75. A shunt system ammeter can be retrofitted on earlier models BUT need to find a shunt value for them. I have an M body ammeter ready to be modified ( installing a 71/74 B body amm face which I have extra ) and replace the full load ammeter on my 74 Charger, but have no idea about the shunt value for it. Aside that, M body amms gets a tiny led what lights up when voltage is low ( or high, can’t recall )

 

[Ethan]

On the back of a factory ammeter, there are two separate wires that bolt onto the ammeter terminals. Ammeters do not have a "positive" and a "ground". They have a "positive-in" and a "positive-out". Note: this is a very basic description of ammeter connections, I could get more technical but it isn't really necessary here.
Back on subject, the thing to do is to connect the 'positive-in' and 'positive-out' connections together. YES, bolt both leads to the same ammeter post and leave the other post 'empty. You have to connect them together to complete the circuit and bypass the ammeter, if you do not connect them together, you will have no electrical power to the rest of the vehicle. So, to recap, the ammeter has two leads, each bolted to a separate stud. Take one lead and put it together with the other lead on the same stud. This bypasses the factory ammeter, without any cutting or splicing of wires. This ONLY works with ammeters. You would NOT do this with a volt meter. It's late, but I can post pictures later.

Thanks badvert, that's easy enough. Does that eliminate the load going through the firewall at the bulkhead disconnects where the fires always start?

 

[khryslerkid]

Thanks badvert, that's easy enough. Does that eliminate the load going through the firewall at the bulkhead disconnects where the fires always start?

That's where they will eliminate the connectors in the bulkhead , drill a hole straight through the bulkhead and run a solid piece of wire through it.

There's a "how to bypass amp guage" on line somewhere. Help me out guy's, I'm out of time this morning.

 

[hunt2elk]

Check out the MAD ammeter bypass on his website, or Nacho-RT74 also has a different twist on it.

 

[Nacho-RT74]

I definitelly don’t bypass the ammeter. There is no need for that when you upgrade the alt. What I make is run a parallel path between amm and sources out of the bulkhead if bulkhead terminals are still good, or replace completelly the bulkhead paths with a new one if bulkhead is already melted and you don’t want to rebuild it.

Several notes can be made about this job.

And don’t worry about get a 100 or 120 amps alt with a 40 amps ammeter. The ammeter will read JUST what battery gets drained when alt is not working or barelly sourcing... or reads what batt gets recharged after a discharge period, won’t read anything else. All car loads are sourced out of the ammeter game AS FAR EVERYTHING IS CORRECTLY SOURCED... i.e: nothing sourced from batt post.


There is a mistake from factory with ammeter being labeled as ALTERNATOR when really is a Batt status gauge.

Of course, after 40 or 50 years of electricity abuses and wrong knowledgement about ammeters that every ammeter must be nowdays checked before keep them in use. Ammeter is a gauge hard to beat BUT STILL everything around it must be checked: isolations, studs still tight into the internal amm shunt... all the unnecessary heat because charge deficiency all these years of abuse get the studs loosen from the internal shunt, what produce bigger failures later.

 

[72RoadrunnerGTX]

You get so much more practical information from a voltmeter and if a voltmeter fails, you won't be left dead in the road.

Tell me about all the “more practical information” a voltmeter provides over an ammeter. Automotive voltmeters provide little more information than a simple idiot light, either charging or not charging. The original ammeters in these cars don’t spontaneously combust, failures at the ammeter connections are typically due to either loose or over-tightened stud nuts, resulting in failed insulators.

 

[RJRENTON]

Gentlemen,
For a high current installation, and you want to know AMPERAGE, I would recommend a shunt system. A shunt is a calibrated resistance that is inserted in the circuit and the AMMETER is connected across the shunt. For example, if you are trying to measure say 100 amps, the shunt will be calibrated to provide say 50 MILLIVOLTS when 100 amps are flowing thru the shunt. The ammeter connected to the shunt will measure the 50 millivolts across the shunt. The ammeter is a MILLIVOLT meter calibrated to show 100 amps. If less than 100 amps are flowing thru the shunt, the millivoltage reading will be proportional. Say if 50 amps are flowing thru the shunt, the millivoltage reading will be proportional or in this example, it will be 25 millivolts. DC systems are easy to underdtand, they are explained using OHM's law: E (expresed as Voltage) = I (expressed as amps) X R (expressed as Resistance) or any combination, such as I=E/R or R=E/R, depending on what you are trying to determine.
As for the wire size needed, my choice would be #8 AWG, type THHN / XHHW, stranded copper wire. This wire is rated at 600 volts (maximum) at 105 degree C temperature rating, and its available in many colors.
Confused?? PM if you need more info.
Bob Renton

 

[bearman]

thanks everybody very interesting read on this subject. everybody have a great fathers day

 

[Mike 71X]

You just re-started my heart. Had my gauge cluster out all winter for some rebuild. Don't have them back yet but wanted to fire the car today. No power! Wondered if related to the gauges being out. Your post answers that question. Thank you!

On the back of a factory ammeter, there are two separate wires that bolt onto the ammeter terminals. Ammeters do not have a "positive" and a "ground". They have a "positive-in" and a "positive-out". Note: this is a very basic description of ammeter connections, I could get more technical but it isn't really necessary here.
Back on subject, the thing to do is to connect the 'positive-in' and 'positive-out' connections together. YES, bolt both leads to the same ammeter post and leave the other post 'empty. You have to connect them together to complete the circuit and bypass the ammeter, if you do not connect them together, you will have no electrical power to the rest of the vehicle. So, to recap, the ammeter has two leads, each bolted to a separate stud. Take one lead and put it together with the other lead on the same stud. This bypasses the factory ammeter, without any cutting or splicing of wires. This ONLY works with ammeters. You would NOT do this with a volt meter. It's late, but I can post pictures later.

 

[Nacho-RT74]

Correct, ign switch gets the power AFTER the ammeter coming from batt. If you don't link the ammeter wires is just like cut the batt power everywhere but starter motor, but without a signal to trigger it or feed the ign system