TheSamba.com :: View topic - voltmeter location and more importantly wiring.

Thu Jan 28, 2010 12:32 am

Hi

I've searched but can't find the details I need.

After my recent troubles with Voltage regulators and battery charging, I'd like to install a voltmeter so I can keep an eye out for when(if) my VR fails again.

location:
I've seen the various location options out there and I'm not that sold on any of them, I'll have to work on that one.

Wiring:
Will this involve running a cable the full length of the bus from the battery? or can I tap of the fusebox somewhere for a reading?

I guess the next question is how easy is it to then set it up to check both batteries, was thinking two sets of wires and a switch?

Thu Jan 28, 2010 6:11 am

Im not sure if this will help. I was having problems with my amp meter and there was some info here that might help you.

http://www.thesamba.com/vw/forum/viewtopic.php?t=396077&highlight=bouncing

Thu Jan 28, 2010 7:15 am

when i install a voltmeter i just run the gauge wire to the fuse panel, to where one of the large red wires is attached. i think it is terminal 30 designation.

Thu Jan 28, 2010 7:25 am

I had my voltmeter connected to the fuse box and noticed that turning the lights on, running the wipers, etc., caused a significant drop in voltage, down to around 12 Volts when running. Now I have a separate wire going to the battery and the voltage is stable at around 13.8. It is more accurate for checking the condition of the charging system.

Thu Jan 28, 2010 7:28 am

voltage should be the same at any feed point in the system. choose a point switched on and off by the ignition; the voltmeter will drain the battery if it's on all the time.

Thu Jan 28, 2010 8:33 am

Mal evolent wrote: voltage should be the same at any feed point in the system. choose a point switched on and off by the ignition; the voltmeter will drain the battery if it's on all the time.

Not entirely true, as I posted. Wire is a resistor, and will have a voltage drop when current is flowing. More current = more voltage drop. V = IR. In my bus, the current in the main wiring harness from the headlights and wipers and such is enough to drop the voltage at the front of the bus 1 or 2 volts. For a more accurate reading, you should read as close to the battery as possible. Or read at the front and just be aware of the fact that the reading will change somewhat depending on what you have running.

Thu Jan 28, 2010 8:36 am

I put one of my meters under the dash on the left side (almost all dash lights are LED).

My other one is mostly for looks, but I like it.. Its a LED bargraph in the radio cutout (the switch is for cabin lights (down is on - german)) it reads from 11v to 14v (on always no draw - got for camping, so I know when to plug in)

Thu Jan 28, 2010 9:56 am

I installed a voltmeter in the blank panel where the clock would of been installed. Just cut a 2" hole in the blank metal cover and installed the gauge. Direct to the battery is ideal except the gauge will always be reading which is a draw on the battery, you could put a toggle switch at the dash to sut it off but then you have to remember to flip the switch. I ran the wire from the gauge to the #30 terminal on the fuse panel. There is slight fluctuations when lights, wiper, heater blower and such are engaged but that is expected, no drops below 12V and you can see when the regulator kicks the alt in.

Thu Jan 28, 2010 10:32 am

WhirledTraveller wrote: Mal evolent wrote: voltage should be the same at any feed point in the system. choose a point switched on and off by the ignition; the voltmeter will drain the battery if it's on all the time.

Not entirely true, as I posted. Wire is a resistor, and will have a voltage drop when current is flowing. More current = more voltage drop. V = IR. In my bus, the current in the main wiring harness from the headlights and wipers and such is enough to drop the voltage at the front of the bus 1 or 2 volts. For a more accurate reading, you should read as close to the battery as possible. Or read at the front and just be aware of the fact that the reading will change somewhat depending on what you have running.

As WT says, it is better to measure voltage directly from the battery. Of course, it is easier to just "plug in" to the fuse box somewhere up front. To switch on the voltmeter with the ignition, use two standard 5 pin relays (mounted in engine compt) that will complete the circuit when the ignition is on. As for monitoring the aux battery as well - since you need to run two wires forward, just run two separate voltmeter gauges. They are relatively cheap, and installing two is just slightly more work, not double the work. The pain is in running the wires forward. Put the aux voltage gauge on the left of the steering column, the main battery voltage gauge on the right, and you'll never be mixed up as to which is which.

Thu Jan 28, 2010 10:46 am

The nice thing about having it hooked up up front is you can actually see your blinkers, and can tell when your brake lights are on, so it helps trouble shoot bad bulbs... I know my charging system is working because it always stays above 12V. Hooked to the battery you only ever see a solid voltage.

Thu Jan 28, 2010 11:46 am

x2, I am re-assured when I step on the brake pedal and see the needle dip a bit that my lights are workin'.

Thu Jan 28, 2010 12:59 pm

dwill49965 wrote: ...As for monitoring the aux battery as well - since you need to run two wires forward, just run two separate voltmeter gauges. They are relatively cheap, and installing two is just slightly more work, not double the work. The pain is in running the wires forward. Put the aux voltage gauge on the left of the steering column, the main battery voltage gauge on the right, and you'll never be mixed up as to which is which.

Or, you can use just one voltmeter and a single-pole/double-throw (SPDT) switch to change the 12VDC+ feed to the meter, allowing you to monitor whichever battery (bank) you choose at any time. True enough, that voltmeters are relatively inexpensive, but it's the cutting another hole in the dash, or adding another damned gauge mount that I hate... unless, of course, you actually like the 'Cessna cockpit' look.

IMO any other available & appropriate gauge location is best used to inform re. actual engine operating conditions, rather than duplication of info that one gauge can show. Clearly that's a personal preference. It's your bay.

Have fun.

Thu Jan 28, 2010 2:03 pm

Better photo of LED volt Gauge:

Thu Feb 11, 2010 2:08 pm

thanks all.. that should be plenty of info to get me going on this.
:D

Thu Feb 11, 2010 6:05 pm

sorry I missed this one and am so late getting to it. We used a VDO volt gauge. A volt gauge is always preferred over a amp meter. If an amp meter goes bad you can lose your charging circuit whereas when a voltmeter fails it doesn't affect anything else. Just pick it up off the switched side of the circuit Scott at German Supply recomended.