Ammeter gauge wiring...

[lil_Blue_Ford]

I have an Ammeter gauge that I got awhile ago for my 2000 Ranger. It got mounted in the truck and more or less forgotten about because I couldn't decipher the instructions that came with the gauge (they give you 3 or 4 wiring options depending on how your vehicle is configured and make no attempt to explain exactly why it works plugging it in between wires for the horn or starter).

So if anyone knows the proper way to wire up an Ammeter gauge, please explain things to me...

The truck is a 2000 Ranger, 3.0L v-6, 5-speed. The Ammeter gauge I have is branded Summit Racing.

Also, after reading about the dangers of running an ammeter in a vehicle, does anyone have suggestions for fusing it in hopes that should there ever be a short, it would pop the fuse before causing a fire? Fuses are cheap, fires are expensive.

 

[shadetree]

For the ammeter to work properly it must monitor all current(amps) being drawn by the vehicle. I don't know why you would want an ammeter, but that is your business.

If your meter is hardwired, it will take a large wire to carry all the current being used by the truck. Usually, this is not good for you have a high current flow inside the truck, and one of the reasons mfgr's stopped using them.

Another type of ammeter uses a coil on the back of the meter to measure current flow. It still requires a large wire, but is not solidly connected to the meter.

Electrical feeds on Fords come from the fender relay, and have fuse links for protection. You would need to combine these feeds, and run the wire from the battery to the meter, then back to the feeds.

This is the standard method, there may be others, but I am not familiar with them. shady

 

[lil_Blue_Ford]

Due to having aftermarket headlights, a stereo, and some other add-ons, I'd like to know if I'm beating my charging system to death or not. I have experienced some weird things before related to my charging system. Thus the ammeter so I can see where I'm at with what turned on (positive draw - alt charging battery, negative draw - alt not keeping up).

 

[Bob Ayers]

I agree with Shady about the problems with an ammeter. If you have an accurate voltmeter, and know how to interpret the reading, you will be much better off. Bottom line, as long as the battery voltage is above about 12.6V (depending on the ambient temp) the battery will not be discharging.

 

[MAKG]

I don't see much problem with 40A through the cab. That's all many of those ammeters can handle. If you're really frightened, you can run some Romex through the firewall. That will take more than 5 times the power the ammeter can handle (remember, it's only 12V). But it's not necessary; you have significant power into the cab anyway through the ignition wire (inside the steering column), and the same 12 gauge wire will do just fine. Or 10 gauge if you want to overdo it.

But the real issue with a direct ammeter is that it functions as a fuse. Any short to ground will blow it out, disabling the entire electrical system. Older vehicles use shunt ammeters, which won't disable the vehicle, but aren't very accurate either.

The best solution would be an inductive ammeter, but I've never seen one of these for sale.

FYI, do not include the cranking circuit in your ammeter or you'll blow it up the first time you start the engine. The only place that includes the whole electrical system except for the cranking circuit is the segment from the starter relay to the power distribution box.

 

[shadetree]

Of course it can be done, but it is just not a good idea. High amperage does a lot of damage if it shorts or doesn't have tight connections. It can set the truck on fire. The wiring currently in the truck carrying smaller amperage can do tremendous damage, speaking from personal experience.

Current electrical systems are much larger than in days past when ammeters were in use, more wiring, devices, etc. If you burn up a wiring bundle in todays vehicles, you have a huge problem. (Ask Dodge about the dash wiring in some of their trucks).shady

 

[MAKG]

Of course it can be done, but it is just not a good idea. High amperage does a lot of damage if it shorts or doesn't have tight connections.

Shady, that's inconsistent with Ohm's Law.

A short to ground WILL give you high current, whether you have a huge 00 gauge wire in there with the entire electrical system connected, or a dinky 22 gauge wire with a single device. As long as there are no resistances upstream, it will draw as much current as its (extremely low) resistance allows. This is a voltage-regulated system; it is not current limited except by fuses.

And loose connections lead to open circuits. I.e., zero current. You can make sparks with high INDUCTANCE, regardless of the resistance.

Ammeters have nothing fundamental to do with the problem of lighting dashes on fire. You can do that by shorting the ignition feed to ground, as well. Or pretty much anything else, like the radio always-on power or the PCM power. Or the power lumbar seats from 1986 RBVs (which were only a fire risk because they were unfused, and the safety recall installed fuses).

 

[Bob Ayers]

I don't see much problem with 40A through the cab. That's all many of those ammeters can handle. If you're really frightened, you can run some Romex through the firewall. That will take more than 5 times the power the ammeter can handle (remember, it's only 12V). But it's not necessary; you have significant power into the cab anyway through the ignition wire (inside the steering column), and the same 12 gauge wire will do just fine. Or 10 gauge if you want to overdo it.

But the real issue with a direct ammeter is that it functions as a fuse. Any short to ground will blow it out, disabling the entire electrical system. Older vehicles use shunt ammeters, which won't disable the vehicle, but aren't very accurate either.

The best solution would be an inductive ammeter, but I've never seen one of these for sale.

FYI, do not include the cranking circuit in your ammeter or you'll blow it up the first time you start the engine. The only place that includes the whole electrical system except for the cranking circuit is the segment from the starter relay to the power distribution box.

With 95A and 130A alternator capacities, even 10 guage wiring isn't going to be big enough!!!

http://fj.asylumbrewing.org/docs/wire-gauge-chart.pdf

 

[MAKG]

With 95A and 130A alternator capacities, even 10 guage wiring isn't going to be big enough!!!

http://fj.asylumbrewing.org/docs/wire-gauge-chart.pdf

Umm, Bob, have you EVER seen a 130A ammeter gauge?

Most of them blow up with a loud POP at 40A or so. 10 gauge is completely adequate for that.

 

[Bob Ayers]

Umm, Bob, have you EVER seen a 130A ammeter gauge?

Most of them blow up with a loud POP at 40A or so. 10 gauge is completely adequate for that.

You just confirmed what Shady and I have been trying to say, don't use an ammeter with the newer electrical systems! With the accessories today, and the alternator capacity (both of these currents will go through the ammeter)
the old 40 AMP ammeters won't cut it!!! Why do you think the newer electrical systems have voltmeters?

 

[MAKG]

The appropriate ammeter is a function of load, not capacity.

Most vehicles draw NOWHERE NEAR 130A. You need SUBSTANTIAL aftermarket electrics in order to get near that.

I had a 40A ammeter in a Bronco II for years. The only thing that blew it was crushing the feed wire with a 2.9L during transmission removal. Dead short to ground; they don't like that.

 

[Bob Ayers]

The appropriate ammeter is a function of load, not capacity.

Most vehicles draw NOWHERE NEAR 130A. You need SUBSTANTIAL aftermarket electrics in order to get near that.

I had a 40A ammeter in a Bronco II for years. The only thing that blew it was crushing the feed wire with a 2.9L during transmission removal. Dead short to ground; they don't like that.

Your DEAD wrong on this one MAKG!!! If you have a discharged battery, with a 130 AMP alternator, the alternator will go to MAX capacity (130 AMPS) to try and charge the battery!!!

Just to verify this, here is Autometer's highest rated ammeter (60 AMPS) and if you notice, they say to only use with electrical systems with alternators
with a 60 AMP MAX output!!

http://www.autometer.com/cat_gaugedetail.aspx?gid=2770&sid=15


So, MAX alternator CAPACITY is key here, NOT LOAD!!!!

 

[shadetree]

A short to ground WILL give you high current, whether you have a huge 00 gauge wire in there with the entire electrical system connected, or a dinky 22 gauge wire with a single device. As long as there are no resistances upstream, it will draw as much current as its (extremely low) resistance allows. This is a voltage-regulated system; it is not current limited except by fuses.

True, but.......the smaller wire will open up much sooner than the larger wire. Fuses don't always do what one would think they would do. In either case, they can do much damage.

Explorers from the time they were introduced to around 1995 had a problem with the mirror switches. The copper printed circuit on the back of the switch pulls away from the circuit board and shorts to ground. The circuit is tied in with the interior lights thru a 15 amp fuse. The fuse never blows.

In my case, it burned the drivers door panel, dash, steering wheel, seat, carpet, headliner, and broke the drivers window, and the windshield. Outside trim, mirror, and paint. It smoked the rest of the vehicle. If this circuit had a large wire feeding it, I would be looking at extensive wiring damage. As it was, the small wire opened up before it could do that much damage to the wiring.

There is a service bulletin on the problem. The fix is to disconnect the mirror from the interior lights, and install its own 10a fuse.

And loose connections lead to open circuits. I.e., zero current. You can make sparks with high INDUCTANCE, regardless of the resistance.

Loose connections generate heat. Loosen your battery cable, then run the starter and see how hot the connection gets. I can't count the times I have tightened connections where it has gotten hot enough to melt the insulation at the connector.

Ammeters have nothing fundamental to do with the problem of lighting dashes on fire. You can do that by shorting the ignition feed to ground, as well. Or pretty much anything else, like the radio always-on power or the PCM power. Or the power lumbar seats from 1986 RBVs (which were only a fire risk because they were unfused, and the safety recall installed fuses).

I'm not talking about the ammeter itself, only in what is required for the installation.shady

 

[lil_Blue_Ford]

So after all this bickering... how the fawk do I wire it up??

 

[MAKG]

Insert it between the starter relay and the power distribution. You need to include every circuit except the starter motor circuit (which will blow it instantly).