Gauge of wire needed for amp gauge?

[SIVAllan]

I'm adding an amp gauge to my Series I v6 car, and am starting from scratch
since the car didn't have one.

What gauge of wire is needed?

The alternator is 63 amps - does that indicate that 6 gauge wire is needed?

Electricity is "a last frontier" to me - one of several

Thanks in advance for any help you may provide.

 

[CRBASIN]

The chart above (from Google) shows wire requirement by length. Six (6) gauge seems like overkill given the wire length required.

Are you planning to replace the entire wiring harness? I installed a new one from Paul A. His added instructions and email support made for an easy job. Well worth the effort in terms of risk reduction. Also consider a new cable from the battery to the engine compartment. My NASA engineer neighbor declared the original one a fire hazard.

John

 

[Barry]

I'm adding an amp gauge to my Series I v6 car, and am starting from scratch
since the car didn't have one.

What gauge of wire is needed?

The alternator is 63 amps - does that indicate that 6 gauge wire is needed?

Electricity is "a last frontier" to me - one of several

Thanks in advance for any help you may provide.

Allan,

Are you determined to use an "original" Alpine amp meter?

Using a "shunt" type ammeter allows accurate current measurement without having to run large wires conducting high current from the engine bay to the dash.

Google "automotive shunt ammeter".

I think a voltmeter provides more "system information" than an ammeter, but that is a different discussion.

 

[Tom H]

Allan, Your alternator can put out 63 Amps, but your system will rarely, almost never, draw that much except quite briefly just after starting or under some fault (short circuit) conditions. Your ammeter wires have no need to be any heavier than any of the other heavy wire in your system, such as the output cable from the alternator. So you can safely use 12 or 10 ga wire. And just as a little lesson here, why would you think that the wire gauge would depend on the output capacity of the Alternator? After all, the ammeter is in place to show current going Into or Out of, the battery. How much current do you think the battery is capable of supplying? A lot more than 63 amps!

John, did your NASA engineer friend say why he thought the original battery cable was a hazard? I am an electrical engineer and find no flaw in that cable, other than that there is no protection - either a fusible link or a fuse- in the line. But if that's the concern then you can add a fuse or fusible link. No different than you would want to do if replacing that original battery cable.

One more thought. What are you using to figure out how/where to wire the ammeter? I have seen several articles that end up wiring the ammeter incorrectly. When wired correctly it will show all current going Into and/or Out of the battery, except current going to the starter.

Tom

 

[SIVAllan]

Thanks fellas.

Tom, I am using a Series I wiring chart, amended a little bit as the factory regulator was removed and the system straight wired.

 

[Tom H]

Allan, That'll work!

 

[SIVAllan]

Tom,

Here's the black face, red needle gauge I stumbled across, next to a stock amp gauge (red needle faded out).

If it works, possibly the stock amp gauge AMPS Lucas Made in England half face will fit.

 

[CRBASIN]

Tom,

My engineer neighbor condemned the battery cable because the insulation become brittle. And he did recommend an in line fuse, which I installed.

John

 

[Tom H]

Allan, It probably / maybe makes sense to use that 60 amp gauge, BUT understand that this results in lower "resolution" of typical operating situations. Unless you have lots of accessories added, other than for the first 2 minutes or so after starting, when the battery is getting recharged from the starting load, the gauge will almost never read more than about 10 amps, and in normal use you will hardly see the needle move. Note for example, that even now, the needle has a slight offset, of about 5 amps indicated. If you were driving during daylight and the alternator quit, your car would only be drawing about 5 amps - from the battery - and the needle would only deflect to the left to about "0" and you'd not even notice the problem on the meter. My Alt is a 35 A alt and typically my 30 amp ammeter needle gets pegged for a minute or so after starting. Sometimes I have to tap the meter face to get the needle unstuck. But I accept that inconvenience as a trade off to get a better indication of how my electrical system is performing and to have a better "tool" for diagnosing electrical issues. Assuming you do go with the 60n Amp meter, I would hope you would post here how it worked out.

Tom

 

[Tom H]

John, thanks. That makes sense. I have not seen brittleness in my cable. I have seen the vinyl insulation of wires running very close to the engine get brittle, but not the battery cable. May be related to avg temp of the local environment.

Tom

 

[loose_electron]

Tom,

My engineer neighbor condemned the battery cable because the insulation become brittle. And he did recommend an in line fuse, which I installed.

John

I have a 350A fuse back near the battery, so if the main battery cable chafes through anyplace, the fuse would pop instead of a meltdown.

As an EE, I strongly recommend a voltmeter over an ammeter. If you got 14V running down the road, your alternator is charging the battery.

Also, if you want reliable, at some point you may want to rewire the car end to end with a more modern wiring harness and proper fuse branches. Pete-Paul A on here sells one that works quite well.

 

[Paul A]

I have a 350A fuse back near the battery, so if the main battery cable chafes through anyplace, the fuse would pop instead of a meltdown.

As an EE, I strongly recommend a voltmeter over an ammeter. If you got 14V running down the road, your alternator is charging the battery..

I absolutely agree with using a voltmeter rather than an ammeter. From a practical matter they are easier to install and are safer. Pete

 

[Alpine 1789]

I had to pull my ammeter to correct an intermittent fault during an Invasion a few years ago. Tiger Tom happened to be nearby at the time, looked at the connections and pointed out evidence that the connections had been heating up. His opinion was that I wasn't far away from a catastrophe. I bypassed the ammeter at the time and later switched to a voltmeter and haven't looked back.

 

[Charles Johns]

Years ago a Street Rod friend almost burned his beautiful 1937 Ford tudor to the ground. AMP meters are tied directly to the battery and any under-dash wires that touch the AMP wires can short the battery to ground. Lots of burned wires under the dash made me think about using a voltage gauge. After that I switched to a voltmeter. I now have an old AMP gauge with wires and alligator clips in my tool kit if I need to check AMPS. If your alternator puts 14 volts into the battery you have an OK system. If it jumps way up and stays there, you have a problem. Once charged the voltage should stay near 12 volts.

 

[Ken Ellis]

"Someone" needs to do a clamp-on Hall effect ammeter that drives a (modified) vintage gauge. Maybe a mashup of a fuel or temp gauge with ammeter face, with possible intermediate control box. No penetration or termination of high-current battery cables, no high-current wiring in dash. Hall effect clamp could be disguised as a firewall grommet or something for the concours guys. You could even still use big wires to connect it if you want the look.

This already exists for the street rod crowd, just need to adapt to Sunbeam land.

Full disclosure: I 'currently' watch amps and volts, traditionally.

 

[65beam]

I had to pull my ammeter to correct an intermittent fault during an Invasion a few years ago. Tiger Tom happened to be nearby at the time, looked at the connections and pointed out evidence that the connections had been heating up. His opinion was that I wasn't far away from a catastrophe. I bypassed the ammeter at the time and later switched to a voltmeter and haven't looked back.

Many years ago Tiger Tom wired the amp gauge in my series 4 and after the restoration I reinstalled it just as he did. Everything was fine for years up until this past July but probably due to the age of the guage it failed in the middle of downtown Pittsburgh. Everything on the car went dead and there we set blocking the flow of traffic coming out of the car show in Schenley Park. Thankfully I always carry a connector to hook the two wires together. Needless to say it's still unhooked and will stay that way. The cars didn't have one when new.

 

[phyrman]

Heres my 2 cents on Amp gauges......dangerous and a Volt gauge is more indicative of charging
My dad added an Amp gauge, but it was mounted on the engine to reduce possible shorting of the heavy gauge wire as it goes thru the firewall

 

[65beam]

I grew up with idiot lights so I don't pay much attention to gauges.

 

[todd reid]

Is there a volt meter to be had that matches the look of the other stock gauges? If I understand Ken's post, I think that is where he was heading? What kind of voltmeters are people currently using?

 

[SIVAllan]

I haven't had problems with Alpine and Tiger amp gauges in the past but I'll chalk that up to good luck, I guess.

I do wonder if a problem would result from an alternator making 60 amps paired with an amp gauge for 30 amps - should the system draw say 50 amps from a new stereo or some other devices being added.