The Stovebolt Site Forums The Shop Area The Electrical Bay Ammeter bypass

I am installing a stock wire harness from scratch on my 1950 suburban. I had planned on not hooking up my Ammeter as it is not that important to me and will save $$$ not having to buy a new 12v replacement.

However....after digging into my wire harness I received from classic parts and I see that the main power runs through the ammeter to power your entire system.

Is there a way to bypass the ammeter safety?

-Cody

Ammeters are not voltage sensitive, just amp capacity, just hook the two wires together schematically. Then hook a wire to your voltmeter, the other side of which you ground.

It is best not to have a swarm of hot wires running around behind the panel, hook the big wires that used to to to the ammeter somewhere easily accessible for future loads and out of the way.

Ed

Here is a post that shows a way to use your original ammeter on a 12V system. There's no need to buy a 12V ammeter. Look at the whole thread as well.
If you do want to bypass the ammeter, like the other guys said, just route those wires to an accessible terminal block that could be used for other loads.

[on edit] Tim beat me to that thread link.

So I read though all that and I think I learned two things..

1. Make a jumper between the + and - on the ammeter.

2. Install some sort of an inline fuse between the starter and the ammeter.

Everything else is wired as usual...correct?

Yes, but make sure the shunt is something other than copper wire- - - -you need enough resistance to cause a little of the charging current to pass through the ammeter so the needle will still deflect +/-. A stainless steel radiator hose clamp works well, protecting the ammeter from high current surges, while still allowing the meter to function as designed. The fusible link is there to prevent a complete meltdown of the wiring harness in case a heavy wire gets a dead short and tries to discharge the battery. I usually place the fuse link at the battery cable connector at the starter.
Jerry

Can you be more specific about the fuse link at the starter...I have no idea what to buy

First time doing this as you can see....

Here's a start for you. Fusible Link
Get the wire gauge as noted in the linked thread. This was just the first hit I got.

It was covered in the thread earlier, but here goes again- - - - -"Reading Is Fundamental". Go to your local auto parts store, to the electrical display, and buy one or two pieces of fusible link wire. A piece about 6 or 8 inches long is plenty. Attach it to the end of the wire going from the battery cable connector at the starter to one side of the ammeter. Connect the fuse link to the charging wire by using a twisted "lineman's splice" AKA "Western Union Splice" instead of a crimped connector. If the wire from the ammeter to the battery cable is a #8 gauge, use a #12 fuse link.

https://www.stovebolt.com/ubbthreads/ubbthreads.php/topics/1310217/1.html

Now, back up a couple of pages on this thread and read the extensive discussion that's already been posted on fusible links- - - -what they are, why they're used, and how to connect them properly. All this information is also available to anyone willing to do a web search on the subject!
Jerry

Thanks Jerry. Dont mind doing the research but I cant help that the subject matter is very challenging to me.

Thank you for the clarification. What seems simple to some is amazingly complex to others (me).

I have a '56 GMC 100 and have rewired the entire truck. In doing so I removed the ammeter and replaced it with a voltmeter. In my research I came to understand that an ammeter was the cause of many a truck fire and their phasing out was a necessity. I was uncomfortable with the fusible link as a solution because I also did not feel confident about sizing, location and effectiveness. I also read that a voltmeter provides more pertinent information than an ammeter. One thing I recall is that the fusible link should be as close to the battery as possible, in fact there are numerous fuses which clamp to a battery post. Do more research on the effectiveness and necessity of the ammeter and if you really feel you need it instead of swapping it for a voltmeter then consult an expert in automotive electrical. It could save your truck. One last thing, because I did experience an electrical fire in my engine compartment (due to a mistake I made) I found it very important to install a cut-off switch. My immediate solution was a quick removal battery connection however, realizing that a fire could occur while driving, I decided to install a cut-off switch in the cab so I don't have to try to get the hood open and remove a battery cable if a fire occurs. Additionally, I purchased a Halon (clean-agent) extinguisher because the traditional extinguisher I used left a tremendous amount of residue and clean up was difficult.

" consult an expert in automotive electrical"

Like for instance, maybe some of us on the stovebolt site who have spent 50 years or more maintaining automotive electrical systems, and teaching it for 30+ years? There are also a few electrical engineers here who can contribute lots of theoretical knowledge and virtually no real-life hands-on experience at making a living by keeping these old rigs running from the time they were brand new.

Welcome to Stovebolt, BTW!
Jerry

Just wire the two wires from the ammeter together either at a junction block or bug them together and tape them off. I did this and use a voltmeter instead. Much safer too!

Ok, I have hose clamp in hand. Still need a fuseable link. Oreillys only had a 14ga. I think Jerry suggested a 12ga. So the search continues. Looks like I'm going to have an ammeter after all.

I was the guy that Jerry helped when I installed the shunt on the ammeter and the fusible link. I used a 14 gauge fusible link and so far it works great. If you read down MY POST that Jerry referenced, drdoug posted, with solid references linked, 4 gauges smaller than the wire you are trying to protect is recommended. So for 10 gauge wire use a 14 gauge fusible link.

I'm putting this thread into a time out.

So.....

I have been doing some reading on the old interweb. Some old Willys jeep guys wire both leads to one post of the ammeter and essentially use it as a junction post. Anybody ever try that?

It will disable the ammeter- - - -the needle will stay centered all the time and you'll have no charge/discharge indication.
Jerry