# Why am I blowing a fuse on my voltmeter?



## PatricioIN (Jun 13, 2008)

ok.. so my 120v charger has a three pronged plug and a black and red wire out put. I have the outputs wired to most neg and most pos on my traction pack. Spliced into those output wires I have some 16gauge wire that goes to a small strip in an electrical box by the charger. Each (red and black) 16 wire is then used to feed the power to the Curtis fuel guage and my voltmeter through inline 2amp fuses on both pos and neg.

I've not had any problems with the Curtis guage, but have blown two fused on the negative line to my voltmeter. Any ideas why or what could be causing this?

note: this is BEFORE I ever plugged in my charger


----------



## PatricioIN (Jun 13, 2008)

Beuhler?? Anyone? lol


----------



## TheSGC (Nov 15, 2007)

Do you have a sketch and what voltmeter are you using?


----------



## etischer (Jun 16, 2008)

do you have the meters probes plugged in the port to read volts, or amps? If you are using the amps port on the meter it will be a dead short, the meter may even be set to read volts.


----------



## ZenDaddy (Jul 22, 2008)

Is your meter from KTA? Is it a westburg? If so, it is pretty foolproof (you are no fool) pos to pos, neg to neg and all that.

Check the continuity across the voltmeter and see if it came to you shorted. 

ZD


----------



## PatricioIN (Jun 13, 2008)

my meters are lcd displays that I picked up off eBay and they were both working fine until I f-d up and stuck a higher than recommended fuse in the one the kept blowing... the one the blows is the negative load lead from the charger wires that go straight to the battery pack.. 

I did stray from the kta wiring diagram in that I pull power for the meters (they need power like the backlit westberg's do) from the power window line (thinking they're only "on" when the key is in "run"). Maybe because that power line pulls more amps - but then why would the only fuse to blow be the voltmeter load ground?....

When I get my new meters, I will redo all the wiring just to make sure I have it all right and be certain NOT to use a fuse that is too big!


----------



## PatricioIN (Jun 13, 2008)

update:

fried ANOTHER SET OF METERS

got my voltmeter back some time ago.. reran the voltmeter load line (according to the KTA diagrams - spliced into charger pos/neg going to batt most pos/neg) voltmeter worked fine after that - no fuse blows... 

got my ammeter back and it seemed to be working fine except that every time I plug in my ammeter, I blow the fuse on the negative load line for the voltmeter...

I can not figure out why this is happening??? The load lines for the ammeter go forward to the motor compartment are wired directly to shunt. The load lines for the voltmeter go back to the trunk and wired to charger output lines.

I have seperated the power lines for both meters (power and ground).. they no longer share any wiring in common except that they are both connected to ignition run. Anyway, in trying to figure out why I was blowing my 2amp voltmeter neg load line fuse, I put in a 10a and popped both meters AGAIN.

Weird thing.. the Curtis fuel gauge is wired to same charger output lines as the voltmeter and has never blown a fuse... WTF??? 

What am I doing wrong??

again, either the ammeter or the voltmeter will both work fine by themselves, but when both are plugged in, I blow a fuse on the voltmeter negative load line.

HELP!

my only thoughts: the kta diagrams show using a 500A/50mv shunt for ammeter and the one that came with my ammeter is a 500A/75mv. Would this make a difference? Even so.. why? the ammeter and voltmeter are not connected! And even if I put a too-large fuse in the load line of the voltmeter, why would it fry the ammeter??? They are not grounded in common. These problems are not affecting any other systems.


----------



## Guest (Jan 10, 2009)

What happens if you hook it up directly to the pack and not through the ignition? Photos would help. How many wires on the volt meter? What is the high voltage of the meter? Maybe your ignition is allowing some sort of grounding effect that blows the fuse. 

Pete : )


----------



## Guest (Jan 10, 2009)

Link to the style volt meter you purchased would help. Did it come with instructions and shunt?

Pete : )


----------



## tj4fa (May 25, 2008)

Let me double-check how I did it again for the LCD 12V 0-200VDC gauge I bought off eBay...

http://cgi.ebay.com/3-1-2-Red-LED-D...emQQ_trksidZp1713.m153.l1262#ebayphotohosting


----------



## PatricioIN (Jun 13, 2008)

gottdi said:


> Link to the style volt meter you purchased would help. Did it come with instructions and shunt?
> 
> Pete : )


http://cgi.ebay.com/Universal-Digit...25411QQcmdZViewItemQQ_trksidZp1742.m153.l1262

this is just like the one I bought.. four pin connector +/- for load and +/- for display power.. ammeter and voltmeter are basically the same but whith different resistors.. The shunt came with it. Each meter works fine when connected alone, but not when both are connected at same time.


----------



## tj4fa (May 25, 2008)

Both LCD units look they can be connected to your 12V iginition system as their power source to run the meters.

I would tap a "hot in run" ignition wire for the 12V positive---> through a fuse (2 amp?) ---> and then on to each LCD gauge's 12V (+) connector terminal.

Then you can run a wire from a common body ground or tap a black harness 12V system ground wire to each gauges LCD 12V (-) terminal. There are no fuses needed on these body to meter ground wires.

On the LCD voltmeter, you can connect to the LCD's meter's positive and negative input terminals from where you have your 120VDC Red (positive) and Black (negative) wires connected for your Quick Charger unit.

On the LCD Ammeter, you need to put your shunt into one (only) of the 120VDC lines in series with it (it's like cutting the cable and connecting the shunt to each end of it). I have mine in front of my motor but some people use it to measure battery pack amperage before the controller (or both).

The two wires from the shunt terminals (16 or 14 gauge) will go only to your LCD ammeter inputs shown in the eBay detail as -negative input and +positive input.

Neither of these are really a ground, they are inputs that if you put one on the wrong side of the meter, would make the needle of an analog meter deflect the wrong way and maybe on your LCD meter give a -120.0 reading if the wires are crossed the wrong way.

As far as you blowing the fuse when you connect the two gauges, you may be tying one of the LCD voltmeter's wires to one of these Ammeter input wires or to the 12VDC system wires that is causing them to short and blow fuses.


----------



## Guest (Jan 11, 2009)

Yes, this is what I wanted to say. Meter power wires are from the 12 volt system and the inputs are from the shunt only. Ground one and poof goes the fuse or meter or both. Watch those grounds and be sure your using the proper one and in the proper place. HV inputs are not grounded. 

Pete : )



> As far as you blowing the fuse when you connect the two gauges, you may be tying one of the LCD voltmeter's wires to one of these Ammeter input wires or to the 12VDC system wires that is causing them to short and blow fuses.


----------



## PatricioIN (Jun 13, 2008)

yeah, I have double/triple/quadruple checked and I have everything wired just the way it shows, just the way you guys have said. That's why I can't figure out why the blowing fuses.... It makes no sense at all that the input wires for the ammeter are blowing the fuse in the 120v input on the voltmeter, they are not connected in any way! Plus, my fuel gauge is wired to the same wires that the voltmeter input is wired to and the fuses for the fuel gauge have never blown. It just doesn't make any sense.


----------



## PatricioIN (Jun 13, 2008)

the only difference I can think of between the voltmeter and the fuel gauge is that the fuel guage is not backlit and therefore not connected to the 12v system at all, but that still doesn't explain why the voltmeter works fine when the ammeter is not plugged in... the negative load line on the voltmeter is pulling too many amps only when the ammeter is connected... serously.. wtf!


----------



## tj4fa (May 25, 2008)

PatricioIN said:


> the only difference I can think of between the voltmeter and the fuel gauge is that the fuel guage is not backlit and therefore not connected to the 12v system at all, but that still doesn't explain why the voltmeter works fine when the ammeter is not plugged in... the negative load line on the voltmeter is pulling too many amps only when the ammeter is connected... serously.. wtf!


Then you need to totally isolate the ammeter wiring from the voltmeter wiring.

12V positive "hot in run" to LCD 12V + 
12V negative (body ground) to LCD 12V -


These are isolated from any part of the 12V system or body as they are transferring High Voltage to the LCD meter inputs

Shunt wire 1 to LCD input - 
Shunt wire 2 to LCD input +


----------



## Twilly (Jan 22, 2008)

The meters from that guy on e-bay are junk. If you read the fine print he sends with the meters, he says that 2 meters cannot be connected to the same inputs and the 12v input has to be isolated from the high voltage input. After blowing 2 sets of his meters, I switched to a higher quality meter with the same wiring, and have had no problems.


----------



## PatricioIN (Jun 13, 2008)

tj4fa said:


> Then you need to totally isolate the ammeter wiring from the voltmeter wiring.
> 
> 12V positive "hot in run" to LCD 12V +
> 12V negative (body ground) to LCD 12V -
> ...


yep... all done

maybe it's gremlins


----------



## tj4fa (May 25, 2008)

PatricioIN said:


> yep... all done
> 
> maybe it's gremlins


Maybe it's like Twilly says....Junk.


----------



## PatricioIN (Jun 13, 2008)

Twilly said:


> The meters from that guy on e-bay are junk. If you read the fine print he sends with the meters, he says that 2 meters cannot be connected to the same inputs and the 12v input has to be isolated from the high voltage input. After blowing 2 sets of his meters, I switched to a higher quality meter with the same wiring, and have had no problems.


do you have a link or source for the higher quality meters? I like the digital display, it's very easy to read.


----------

