Volt vs. amp meter (1 Viewer)

[1Fine40]

Question: Why did Toyota apparently only offer ammeters in their FJ-40's? Or were there voltmeters as options??
2nd question, why is one necessarily better than the other?? Which one would you want and why? Just trying to understand the logic of the TEQ engineers....

(I personally hate the ammeter cause it doesn't really tell me an awful lot..)

Cheers!

 

[llih]

Go with a voltmeter. I don't think Toyota offered one at the time. Voltmeters are easy to hook up and you don't have the high amps routed into the dash. I was going to replace my stock guage with a SW ammeter, but changed my mind and went with a voltmeter. There was an article/link on the difference between voltmeters and ammeters that was posted here a while back. Try a search

 

[IDave]

I'll put in my vote for the ammeter, myself. It is very sensative and tells me a whole lot: When and if I'm drawing, whether my charging system is working. The volt meter tells me when my battery's gone dead. I'll know that when it doesn't start.

 

[BC Cruiser]

I liked my amp meter in the dash, it told me how much of elec load I was putting on the alt. I won't put one back in because for one you have to find a amp meter that's rated bigger then the output on the alt, and I don't like fact that theres large gauge wires in my dash. I'm putting a volt meter in place of the amp meter.

A amp meter works buy routing all the power from the alt through the meter then to the battery. So if your not using much power then it will read in the + range, but if you use your winch then it will read in the - range because your using more power then the alt is making.

A voltmeter can be pluged in were ever, because it acts like a pressure gauge.
Look at a wire like a water pipe, and electricity as the water. Voltage is the pressure of the electricity moving down the line, thats why you can put a volt meter anywhere, because its just reading the elec pressure and theres no flow moving through it. Amperage is the flow of elec moving through the line, in order to measure this you have to route all the electricity through a gauge, it works like a flowmeter on a pipe.

Hope I helped and didn't confuse you.

 

[Pin_Head]

This issue has been beat like a red head stepchild.

Search and

+1 for the amp meter.

 

[Mark W]

I prefer both.

This horse is a greasy spot on the ground by now. But there's always new folks coming along.


Mark...

 

[osagecruiser]

after reading all the info on both guages i too installed them both...

osagecruiser

 

[1Fine40]

Hmmmm. Where exactly did you search? I just did a few searches for volt meter and ammeter, and didn't find much...
I guess it really boils down to the fact that Toyota did not have an optional volt meter....(I wish they did) I didn't like the thought of punching yet another hole in my dash for something! I also have added a 140 amp alternator, and that doesn't work so well with the stock gauge....So, I'm rewiring kinda like the attached drawing from Mad Electrical... Can you all see anything you don't like about this??
Cheers!

 

[Pin_Head]

Hmmmm. Where exactly did you search? ....So, I'm rewiring kinda like the attached drawing from Mad Electrical... Can you all see anything you don't like about this??
Cheers!

I used amp + volt + meter in advanced mode and this came up:
https://forum.ih8mud.com/showthread.php?t=79285&highlight=Amp+volt+meter

That wiring diagram will work fine for a 140 amp alternator, but some of the things shown in the diagram don't apply to cruisers. MAD electric is a peculiar combination of useful information, things that are true but not really that important (remote sensing, running your headlights off of a relay system to avoid 0.5V voltage drop) and total BS (amp meters are worthless old school technology).

 

[FJ40_owner]

Amp vrs Voltmeter

Actually there are two types of Amp meters available. The cheaper and more dangerous ones run all the high alt current through the meter in series. Very dangerous!

Another style on many vehicles is a shunt type, that is a known resistance/voltage drop on one leg of the Alt output. Then you need only run 16 Ga wires to your meter because your are actually measuring Millivolts. Very accurate, pricey and not generally available at Napa.

Voltage is equally important because it is an indication of your batteries condition and your electrical system as a whole. If installed be sure to put it in series with a run relay contact or you'll drain your battery over time.

If I could only have one I would prefer amps, via the shunt. The largest range you can purchase (if you winch and or have dual batteries or lots of Ham or lights) I am able to watch the load and charging directly off my alternator, My accesories draw LOTS of AMPS

I liked my amp meter in the dash, it told me how much of elec load I was putting on the alt. I won't put one back in because for one you have to find a amp meter that's rated bigger then the output on the alt, and I don't like fact that theres large gauge wires in my dash. I'm putting a volt meter in place of the amp meter.

A amp meter works buy routing all the power from the alt through the meter then to the battery. So if your not using much power then it will read in the + range, but if you use your winch then it will read in the - range because your using more power then the alt is making.

A voltmeter can be pluged in were ever, because it acts like a pressure gauge.
Look at a wire like a water pipe, and electricity as the water. Voltage is the pressure of the electricity moving down the line, thats why you can put a volt meter anywhere, because its just reading the elec pressure and theres no flow moving through it. Amperage is the flow of elec moving through the line, in order to measure this you have to route all the electricity through a gauge, it works like a flowmeter on a pipe.

Hope I helped and didn't confuse you.

 

[FJ40_owner]

You are Crazy

To run all that current into your dash and into a meter. Get a shunt and a millivolt meter. Simple, accurate and safe.

Hmmmm. Where exactly did you search? I just did a few searches for volt meter and ammeter, and didn't find much...
I guess it really boils down to the fact that Toyota did not have an optional volt meter....(I wish they did) I didn't like the thought of punching yet another hole in my dash for something! I also have added a 140 amp alternator, and that doesn't work so well with the stock gauge....So, I'm rewiring kinda like the attached drawing from Mad Electrical... Can you all see anything you don't like about this??
Cheers!

 

[1Fine40]

To run all that current into your dash and into a meter. Get a shunt and a millivolt meter. Simple, accurate and safe.

Apparently you are not looking too closely at the diagram...the charging current does not run through the firewall......All high drain items are kept in the engine compartment such as E-fan and headlight relays, starter solenoid etc. I like the shunt idea, and will look into it. I wonder if the Toyota stock gauge is a shunt type? I can't believe those tiny wires can handle +- 30 amps!!!

Cheers!

 

[FJ40_owner]

My mistake

I thought the thing where the wire from the alt connected was the meter. In any case high current from an alt to a meter is unsafe. I know people who have burnned up their wiring harness jump starting someone, cause all that current goes through the firewall, into the meter and back to the loads.

Apparentley you are not reading what I wrote. A shunt type Amp meter measure Milli Volts, that is thousands of a volt. Kinda small.

Apparently you are not looking too closely at the diagram...the charging current does not run through the firewall......All high drain items are kept in the engine compartment such as E-fan and headlight relays, starter solenoid etc. I like the shunt idea, and will look into it. I wonder if the Toyota stock gauge is a shunt type? I can't believe those tiny wires can handle +- 30 amps!!!

Cheers!

 

[CruisinGA]

Apparentley you are not reading what I wrote. A shunt type Amp meter measure Milli Volts, that is thousands of a volt. Kinda small.

What he means by remote shunt ammeter is that you only have to route milliamps into the cab for the guage, the shunt itself sees the full current, not that it can only handle milliamps.

 

[1Fine40]

Yeah, I get what you are saying. If you look at the Toyota wiring diagram, it appears that the unit in our FJ-40's (maybe 55's too) is a shunt type meter...it just doesn't have the range necessary for a larger alternator....? At least that is what I see in my FSM...

Cheers!

 

[Pin_Head]

I wonder if the Toyota stock gauge is a shunt type? I can't believe those tiny wires can handle +- 30 amps!!!

All amp gauges above the milliamp range have a shunt. It is just a question of whether the shunt is internal (built in to the gauge itself) or whether it is external. Older (pre '78) Toyota amp meters have an internal shunt. It is the strip of metal between the two electrical connection posts. Note that if you stack these shunts, you can double or triple the amp capacity of the stock gauge.

Voltage is equally important because it is an indication of your batteries condition and your electrical system as a whole.

Not really. Your battery could read 12 V and not have enough power to start your truck. Your system could read 14.8 V running all day and your battery could be discharged. It does indicate that your alternator is working, but so does an idiot light.

In any case high current from an alt to a meter is unsafe. .

It doesn't have to be unsafe.

If the high current sources (battery, alternator) have a fusible link of the appropriate rating, it will blow if a short occurs. In any event, there is no avoiding high current going into the cab as the chassis of a cruiser can sink about 60-70 amps wiht everything running full bore at once.

 

[1Fine40]

In any event, there is no avoiding high current going into the cab as the chassis of a cruiser can sink about 60-70 amps wiht everything running full bore at once.

So very true! That is why Toyota ran a 10 gauge wire from the alternator into the gauge cluster! The small wire i was referring to may just be the fusible links on either side of the meter! I might try stacking up a couple of those shunts you mention to increase the capacity of the gauge....would be mucho better than seeing it pinned from time to time!! Thanks for the idea!

Cheers!

 

[CruisinGA]

So very true! That is why Toyota ran a 10 gauge wire from the alternator into the gauge cluster! The small wire i was referring to may just be the fusible links on either side of the meter! I might try stacking up a couple of those shunts you mention to increase the capacity of the gauge....would be mucho better than seeing it pinned from time to time!! Thanks for the idea!

Cheers!

If you increase the capacity of the ammeter, you should also increase the capacity of the wire to and from the ammeter, that is more the cause for concern than the guage itself. (Hence the reason an external shunt ammeter is the best solution)