The stock amp meter on my 54 did not work so when I pulled the gauge cluster there was just a clamp loop on back no electrical connections.
When I check the schematics for it I find 10 gauge wire running from selonoid through clamp bracket then to headlight switch. Is that right?
With a 12v conversion would it still be #10 wire?
I've never seen something like this before.

 

the amp meter is inductive (no electrical connection) the wire passing through it (headlight supply wire) is how it was built... now if you are converting to 12v almost everyone switches to volt meter (at idle you will see 12v at any rpm you will see 13.8v on a normally working good charging system).
you left out the words fuse - everything should be fused or relayed, so yeah get ya a fuse/relay in there somewhere.

headlights pull a lot of juice, 10ga is correct.

If it was me and I was doing it again, i would look for the right 70's volt meter you can canibalize and fit in then either reskin it or buy a new one from parts house.

I believe "Julie" had a lot of diagrams on the amp / volt meter - do a search for julie electrical

Are you putting in an alternator, 12v generator, or?

 

Thanks Brian, yes the truck has a 12v GM internal reg ALT. The stock gauges right now only fuel works and I don't know how. When dad converted from 6v- a friend of his came over and ripped it all out and used old loomes to make a new one. I have the wiring harness from a 63 f100 but it only has a light. The aftermarket gauge I put on 14 yrs ago works more like an old Chrysler showing both drain and charge. I want all old gauges to work. I may buy th OE style from mid 50 that is volt gauge.
Truck does not have more that 2 fuses on it but has a circuit breaker in headlights (or so I was told). What if I ran the #10 wire that goes to key switch through amp meter. I may try and see how I wired the aftermartket and see if it might work.

 

amp meter is a "flow" meter - my understanding is that only the portion of the power that is being consumed (or recharged) through <b>that</b> circuit is shown. if you want your amp meter to read the entire flow in the system you'd have to have a huge 6ga wire running first from battery through amp then to distro block - a horrible idea since that is an unfused and highly dangerous setup.
To answer your question taking the key switch and running that line through the amp meter would work fine - gives you different info than the headlight though.

amp meters in my opinion aren't that good because they don't tell you "at a glance" how well your system is working they tell you at a glance if you are charging or discharging... when you are fully charged then there is no real flow and the gauge shows nothing.
(now if you pay attention to the gauge a lot, you can get a better feel for how the system is working by looking at the long term picture - they also tell you if your battery is not holding charge better than a volt meter IF you know how to read em).

Volt gauge tells you at a glance if the alternator is working (13.8v or no), if your batter is discharged (engine off, what's the volts - a fully charged 12v battery is 13.8), etc - more useful IMHO since people don't pay attention to their guages.

I think the harness which only has a light will power a volt meter just fine (put a volt meter on the line listed for the light)

 

Is there a 12 volt meter that will match the instruments in a 49?

 

The stock arrangement does measure all power flows, not just the headlights. The wire from the battery goes thru the loop, after which it connects on a post where the generator output is also connected. If the generator is charging the battery, flow in the wire to the battery is reversed, showing "Charge".

 

Ok thanks Ross that helps, but another dilemma. I read on HAMB that the temp gauge can be used as a volt gauge. I would need to change word but does this sound right? it did to me but .....
A) how would I wire it? simple power wire in and out on Acc side of key?
B) changing lettering to look stock.
C) should I even consider it?

 

It may be beneficial to look at it a little differently. Assuming that the ammeter is sensing the charge/discharge between generator (or alternator), battery, and current consuming circuitry such as headlights, then the meter would indicate as follows:
Negative - supply is not keeping up with demand at present. If this condition persists, either the wire is run through the sensing loop backwards or you have troubles that need attending to.
Positive - the battery got a little low and the charging system is replenishing the charge. This is to be expected after cranking the engine, etc.
At or near zero - the battery has been recharged and the system is regulating properly.

The key is that a regulating system will, after reaching balance, read at or near zero. That is the whole point of regulation. Of course, headlights, wiper and blower motors and other accessories will show additional current draw when on. Mathematically, one could think of them as an offset.
That being said (typed) it is absolutely correct that battery voltage is also an important indicator. However, solely observing battery voltage while parked (after a brief rest) will typically not show signs of overcharging until it is too late. An ammeter will make overcharging obvious during the drive. Thus, the two can be used together to best monitor the charging system's health.
I do not have a voltmeter in the dash but I pop the floor panel and check the battery's health about once a month at the same time that I check brake fluid level.

 

Truth be told, an idiot light (on an alternator) is a pretty useful alternative to either the ammeter or voltmeter. With an alternator the ammeter on my truck only deviates from 0 for the first 30 seconds or so after a start.

Kurt, can you link to that HAMB article? I can't think how it's possible to use the temp gauge without internal mods as a voltmeter, it has a bimetallic element in it. I wouldn't want to give up my temp gauge anyway.

 

Ross, I was wrong it's not on HAMB but it's here.
http://www.systemv.us/clemmie/finish/
Wrong page sorry I saw this in my history but still thought you might like it.

 

That makes more sense, having dual temp gauges on a flat V8.

 

Yes it does but somewhere I still have where they switched a temp to volt and took off the BATT gauge face and put it on the TEMP gauge. I think it still went through a voltage reducer. I have some mid 60's gauges and I think I will play and see what I find. Result to be posted and pictures if successful.