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Can anybody tell me the maximum current usage of a def110 CSW which is completely standard

as I have a ±30A guage and am wondering if it'll be any use?

The ammeter measure current going to and from the battery, so the total current useage of a vehicle doesn't really apply unless you're going to sit there with the engine off and everything electrical switched on.

That said, I had an old rangie with a 50-0-50 ammeter fitted and this went to full scale charging just after starting the engine, so I would suggest a 30-0-30 would be a bit on the low side.

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As a std vehicle has a 65A alternator I would say you should fit a 65A or maybe 100A ammeter - if you start the vehicle with a flat battery it will go to full output on the alternator, and I should think if you whack everything on it would probably be close to that anyway:

2 x 60W headlights on main beam = 10A

4 x 5W sidelights + number plt light - ~ 2A

Heated rear screen - 20A?

Both wipers probably 10A

Cigarette lighter - 20A?

Heater fan

Radio

Instrument lights

Interior lights

etc etc etc

Also the meter needs to be in the right place - i.e. not with the starter motor current going through it!

I personally think a voltmeter is a lot more useful than an ammeter - and if you whack everything on like that on a 300Tdi (my old 90 had a V-meter fitted) you could see the voltage drop right back.

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Ammeters are an incident looking for somewhere to happen

Noooooo

Ammeters support "smoke theory" voltmeters don't ;)

Ammeters measure the amount of smoke travelling through the wires, and indicate this to the operator by the amount of smoke they emit when something shorts out, thus providing an immediate and obvious scented visual warning to the driver that something is amiss - far more attention grabbing than some boring voltmeter needle wafting back and forth :)

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Noooooo

Ammeters support "smoke theory" voltmeters don't ;)

Ammeters measure the amount of smoke travelling through the wires, and indicate this to the operator by the amount of smoke they emit when something shorts out, thus providing an immediate and obvious scented visual warning to the driver that something is amiss - far more attention grabbing than some boring voltmeter needle wafting back and forth :)

The two meters give different information. An ammeter will tell you if the charging system is working, or if you're draining the battery faster than the alternator can charge. A voltmeter indicates the state of the battery - it will drop as the battery is discharged, but it's slower to show than an ammeter.

Fit both and be permanently worried, or neither and live in blissful ignorance ^_^ !

Jim

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I used to have both, but now I just have a voltmeter. A proper car voltmeter starts to indicate at about 8 volts and full scale is 16 ish so it gives a good indication of whats going on.

The voltage drops if the battery stops charging, you soon get the feel for where the needle should be.

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Thats it as RTB has said, a voltmeter gives you all the information you will need.

Ok, lets try and explain this;

i) engine is running but your volt meter shows 12V or below, suspect alternator has packed-up or not charging fully. If you have overloaded the system however, the voltage will be pulled down so switch off all non-essentuals to make absolutely sure!!!!

ii)engine is running and the volt meter shows between 12.7V and 14.5V; alternator feeding good, relax and enjoy.

iii)engine is running and the volt meter shows 15V plus; switch it off pretty soon as your regulator (the device that limits the voltage coming out of your alternator) has probably fried and is about to start frying the rest of the voltage sensitive items in your vehicle. Normally a good hint is your lights become more brighter than what they normally are.

although the above is reasonably gough and ready, it gets you through most scenarios. An ammeter however tends to only tell you if you are charging ok, charging a heavily discharged battery, or telling you your alternator is totally dead and your battery is supplying all the wigglies.

However an Ammeter is not a weak link in a circuit, no device should be epected to take full dicharge from a battery when something else fails, thats due to the installation person/owner not providing suitable circuit protection to protect all other devices, inclussive of the ammeter.

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