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Sat Jun 16, 2007 5:21 pm

Hey Guys,

I bought a few VDO gauges today for my bus. Besides oil temp, pressure and a tach I got an ammeter.

All of the gauges installation is pretty straight forward, however I am stuck with some questions about the ammeter. I looked for a wiring diagram of the ammeters and found this one:

http://egauges.com/pdf/vdo/0-515-012-154.pdf

It kinda suprised me it had to be wired like this. I thought you could just wire it over the battery but this doesn't seem to be the case. Also I read the wires will have to bear quite a load. So I have a two questions.

Should I wire it like in the diagram, or is there an easier way?
What kind of wire diameter should i use?

Sat Jun 16, 2007 5:56 pm

..Do you have a gauge from VDO..? if so it's alot easier.you will not have to run heavy gauge wire to the back.

Sat Jun 16, 2007 6:07 pm

Honestly, an ammeter is a waste of time.

You need a shunt to connect one and it seems a long way to go for a gauge that doesn't tell you much.

A voltmeter is a better choice for state of charge and much more fun. It actually moves! :lol:

Sat Jun 16, 2007 7:31 pm

Duncwarw wrote: Honestly, an ammeter is a waste of time.

You need a shunt to connect one and it seems a long way to go for a gauge that doesn't tell you much.

A voltmeter is a better choice for state of charge and much more fun. It actually moves! :lol:

Ditto to what Duncwarw said. A voltmeter will tell you far more than an ammeter and is way easier to install.

Sat Jun 16, 2007 7:39 pm

I also agree to that,if you gotta have another gauge

Sat Jun 16, 2007 8:06 pm

If you put it in, you have to wire it the way the diagram shows.
I put in a 30 amp gauge because it's old school. From a practical standpoint, a voltmeter is probably more useful though.

I used 6 AWG THHN/THWN stranded copper wire and a 40 amp fuse, but what you need depends on your electrical system.

Rob

Sun Jun 17, 2007 4:01 am

Yep- I use volt meters also. They give a better overall analysis of the electrical system. And very easy to wire.

Sun Jun 17, 2007 5:31 am

MadMax78 wrote: Hey Guys,

I bought a few gauges today for my bus. Besides oil temp, pressure and a tach I got an ammeter.

All of the gauges installation is pretty straight forward, however I am stuck with some questions about the ammeter. I looked for a wiring diagram of the ammeters and found this one:

http://egauges.com/pdf/vdo/0-515-012-154.pdf

It kinda suprised me it had to be wired like this. I thought you could just wire it over the battery but this doesn't seem to be the case. Also I read the wires will have to bear quite a load. So I have a two questions.

Should I wire it like in the diagram, or is there an easier way?
What kind of wire diameter should i use?

old DKP driver wrote: ..Do you have a gauge from VDO..? if so it's alot easier.you will not have to run heavy gauge wire to the back.

Duncwarw wrote: Honestly, an ammeter is a waste of time.

You need a shunt to connect one and it seems a long way to go for a gauge that doesn't tell you much.

A voltmeter is a better choice for state of charge and much more fun. It actually moves! :lol:

Wildthings wrote: Ditto to what Duncwarw said. A voltmeter will tell you far more than an ammeter and is way easier to install.

old DKP driver wrote: I also agree to that,if you gotta have another gauge

Hippie wrote: If you put it in, you have to wire it the way the diagram shows.

I put in a 30 amp gauge because it's old school. From a practical standpoint, a voltmeter is probably more useful though.

I used 6 AWG THHN/THWN stranded copper wire and a 40 amp fuse, but what you need depends on your electrical system.

Desertbusman wrote: Yep- I use volt meters also. They give a better overall analysis of the electrical system. And very easy to wire.

Sorry to contradict all you folks, but an ammeter isn't useless, nor is it replacable by a voltmeter; the two instruments are complementary!

A voltmeter will not indicate whether a lead-acid battery is charging or its state of charge; showing virtually the same voltage until the battery is 90% discharged. What it will usefully show, is the regulated voltage output, of the generator (i.e. dynamo or alternator) when operating and the battery's output voltage, when under load (e.g. cranking the starter motor), with no gererator operating.

An appropriately connected ammeter, will indicate whether the battery is charging or discharging and at what rate, but this only gives instantaneous values and requires some memory of what has been occurring over a period of time. There are some more sophisticated digital instruments, commonly made for the leisure marine industry, which integrate charging rate over time (i.e. as in mathematical, integral calculus), to indicate the actual level of charge stored.

If one is content to fit just a voltmeter and ammeter, then the most appropriate type for the rear-engined VW, with rear-mounted battery, is the remote-shunt ammeter, whose shunt resistor, is connected in series with the alternator to battery connection and the ammeter connected in parallel across the shunt resistor, using light-duty cable, of perhaps no more than 0·5 mm².

The more commonly available, internal-shunt ammeter, has its shunt resistor, mounted inside the instrument housing. The shunt resistor, is still connected in series with the alternator to battery connection and the ammeter connected in parallel across the shunt resistor, but because the shunt resistor is located at the front of the vehicle, mounted within the dashboard, one obviously needs heavy-duty extension cables (e.g. 6·0 mm² or greater), to extend the alternator to battery connection cable, so that it can be routed via the dashboard in the cab.

At sometime in the future, I hope to modify a VDO internal-shunt ammeter, by removing its internal shunt resistor and substituting into the circuit, a remote-mounted (i.e. in the rear engine-comportment) external resistance shunt; probably adapting the removed internal shunt resistor, for the purpose.

Regards.

Nigel A. Skeet

Sun Jun 17, 2007 6:30 am

I have made my own shunts for testing in industrial applications, using heater wire, with good results.

Rob

Sun Jun 17, 2007 8:50 am

Thanks for all the replies. I was almost ready to throw my ammeter overboard and get a voltmeter. I'll probably just take the effort to install the ammeter. I'll be pulling wires from front to back anyways for the oil pressure, oil temp and tach.

old DKP driver wrote: ..Do you have a gauge from VDO..? if so it's alot easier.you will not have to run heavy gauge wire to the back.

I do have a VDO gauge (-30,0,30 A), but it appears these have a internal shunt. So why would I not have to run the heavy wiring?

Sun Jun 17, 2007 10:13 am

MadMax78 wrote:
old DKP driver wrote: ..Do you have a gauge from VDO..? if so it's alot easier.you will not have to run heavy gauge wire to the back.

I do have a VDO gauge (-30,0,30 A), but it appears these have a internal shunt. So why would I not have to run the heavy wiring?

You will have to run the heavy wire, unless you take NASkeet's suggestion to change (one way or another) to a 'remote shunt' resistor setup.

Reason: the supply for every electrical device, except the actual starter motor, is essentially routed through the ammeter. My Westy's 60-0-60 VDO ammeter is wired with #4AWG cable(EU size 32· mm²). That's a lot of copper wire, but it also serves as a quality supply line to various camping devices along its path(on the 'load' side.

Having both ammeter and voltmeter is definitely nice, because with just a voltmeter, we tend to infer a lot of what an ammeter would be telling us. As NASkeet pointed out, the ammeter tells you right away about a charging problem, as it's happening.

OTOH if only one power condition gauge is to be mounted, like most have said, I'd go with a voltmeter, and have done so in several of my vehicles.

J.R.
68 Westy
(+ others)

Sun Jun 17, 2007 10:21 am

To avoid very heavy wires running from back to dash;
I do not understand why they don't put the shunt ( a high Amp very low value resistor ) at the back, between +Battery and +Alternator and run light gauge wires to the meter to sense the shunt's voltage drop.
This is basic high Amps measurement.

Sun Jun 17, 2007 10:29 am

If you must install it then do it correctly, using heavy cable. A possible source is "Monster Cable", used for high wattage car-audio purposes. it looks nice and is very flexible. gus

Sun Jun 17, 2007 11:37 am

One reason for not having an ammeter with an internal shunt is that if the ammeter fails you lose electrical connectivity between your charging system and your battery. The same is true if the shunt or its connections fails on a remote shunt system. An ammeter is one more unneeded complexity to an electrical system.

You can tell close enough with a voltmeter if a system is charging or not. If the voltage is about 12.5 it is charging and if it is less it is discharging. If a voltmeter fails then your electrical system is not compromised.

If you don't want to have electrical problems then the two most important things you can do are first to keep your engine in tune so it starts easily in all conditions and secondly is to check the brushes and bearing in your alternator and starter as soon as practical after buying a used vehicle and then check them again at reasonable intervals thereafter, like once every 80,000 miles.

Neither an ammeter or voltmeter can tell you if an alternator bearings are worn to the point of failure or if the starter brushes are just nubbins.

Sun Jun 17, 2007 12:03 pm

electricall issues are hard and specially sporadic failures in the charging system, even if you have a voltmeter and an ammeter conected the right way sometimes it is hard to find out that you have a burn/open diode in the diode plate or that youre cables are very resistive due to long periods of working under heavy load, been washed, and getting hot most people i know when confonting an electrical failure tend to think "ohh well the battery is bad" and go get a new one, when in fact the battery is just fine, same thing aplies to the alternator/generator..

if you intend to service your charging system you need more than an ammeter or a voltemer on the dash, you need to take the batery out :wink: once in a while, check the water level on each cell, change your terminals and sand any ground conections, check for old cables, disconect at least one batery terminal if it sits put for a long period, etc. etc. this will help you understand what is goin on, and help you grow the necesary skills to find where the problem lies...

Sun Jun 17, 2007 12:51 pm

I'm not getting this ammeter to indicate the health of my electrical system. The reason why I got it is to be able to see if the battery is being charged or discharged.
I don't want to be draining my battery while driving when I got all my aux equipment running.

However, I'm starting to have my doubts about installing it...

Sun Jun 17, 2007 3:05 pm

You'll like it. Just install it right--without taking shortcuts. I like mine.
I could live without it, but I'm glad I put it in.

Rob

Sun Jun 17, 2007 3:11 pm

Okay, install a voltmeter first. Then if it throws happy indications to you, and you never have problems... you really didn't need the ammeter!

OTOH if the voltmeter patterns suggest problems, you can always add an ammeter, to help you further diagnose & correct the issues.

Start off your wiring adventures with good quality, heavy-duty battery cables & terminals. Solder all terminals, even if you've first crimped them, and don't skimp on wire sizes, fuses, circuit breakers, and switches. Protect any wires that are subject to physical abrasion by other objects with heavy plastic or textile covering, in addition to the wire's own insulation. Make sure plugs have full contact with sockets & aren't wiggling around, causing arcs & sparks.

If a camper, it helps to admit that your ideal range of 'camping necessities' may be quite different than either VW or Westfalia had in mind, so the vehicle's wiring needs might be very different also. My '68 Westy was factory-equipped with aluminum wire in its 120VAC circuit. That was a horrible choice for a moving, flexing vehicle, and all was replaced with copper when I added more AC outlets.

Be safe. Have fun. Make it yours. Best wishes.

J.R.
68 Westy
(+ others)

Mon Jun 18, 2007 1:15 am

No biggie! Either gauge will give you a lot of valuable info and tell you of an electrical system overall malfunction or change in the way it's all functioning. You need to run wiring anyway so running a big wire for the amp. is no inconvience.

I didn't have to run a wire for an anp meter but needed wiring for press, temp, tach, radio memory bypassing the cutoff switch, security, etc. So it turned out nice running a new harness thru all the frame holes parallel to the stock harness. And finally zeroed in on using vinyl tubing from home depot as the sheath. And used silicone spray to lube the wires when pulling the bundle through. Yes, solder the connections and using shrink tubing over the connectors is nice.

Years ago, I had an amp meter melt down due to all the juice running thru it. It was a top brand but the plastic housing just melted. Could have shorted against the car and caused a massive problem. The volt meter would just blow a fuse if it failed.

Mon Jun 18, 2007 6:21 am

NASkeet wrote: There are some more sophisticated digital instruments, commonly made for the leisure marine industry, which integrate charging rate over time (i.e. as in mathematical, integral calculus), to indicate the actual level of charge stored.

As I previously mentioned, there are some more sophisticated digital instruments, intended mainly for leisure marine applications, which enable one to more easily monitor and manage the battery charging and state of charge storage, as follows:

Merlin Equipment Limited trading as Power-Store
Units 3 & 4, Cabot Business Village
Holyrood Close
Poole
Dorset BH17 7BA

Tel: +44 (0)1202 697979
Fax: +44 (0)1202 691919

e-mail: [email protected]

http://www.power-store.com/?id=160

http://www.power-store.com/view-item.asp?itemid=1261&id=160&

http://www.power-store.com/view-item.asp?itemid=954&id=160&

This is an example of some of the available-instrument specifications:

Battery voltage for up to three battery banks
High/Low battery voltage alarms for each battery bank
Selectable Legends tell you exactly which battery you are looking at. These can be changed to: Start Batt, House Batt, Port Start, Stbd Start, House 1, House 2, aux batt, genset, radio batt, winch, bowthruster & van batt.
Net Current (Amps) in or out of domestic battery bank
% Remaining in domestic battery bank
Amp Hours Remaining in domestic battery bank
Low Amp Hours Alarm
Free alarm contact - a contact on the back of the meter allow you to fire remote alarms or even an auto generator start.
Green backlight (comes on when a button is pressed or can be wired to the rest of your instrument backlighting system.
Very simple installation
Supplied with 450A 50mV Shunt

Regards.

Nigel A. Skeet