Unless you really want an ammeter, don`t wire it in. They are a leftover from generator days. The problem is they create VD !
Voltage drop ! and heated wiring. If you are running an EFI engine, then the electrical load will be way more than the original engine. A solution may be to get an instrument repairer to change it to a voltmeter, using the face of the ammeter. So it will look original. Get him to calibrate it so at around 14 volts, the needle is into the `C` charge (R/H) side. Hope this helps. Peter

Thanks gents

My cars running VN wiring in the engine bay down to all the fusable links and relay/fuses in the engine bay.

So theres only 2 wires coming off the battery (a 20g to the starter and a 8g to the generator + a little white one that also goes to the generator).

A cable then comes back to the fusable link bus bar and then everything else comes off that.

I need to work out where the feed to the HG fuse box comes from - not sure if all of that makes any difference to your suggestions??

Thanks and Cheers

Jeremy

The G will roll again....

Not sure about some of the comments on ammeters and generators here.

Generators also work on having their output voltage higher than the battery to charge. The only differences between an alternator and generator are:

1) Magnet spins in alternator coil stationary, coil spins in generator, magnets stationary.
2) Alternator uses electronics to make DC from AC output, Generator uses mechanical rectifier to turn AC to DC.
3) Both use regulator to adjust field current to regulate output voltage.
4) Both deliver current dermined by the difference in terminal voltage of battery and terminal voltage of alternator/generator divided by internal resistance.
4) Alternators are often refered to as generators.

The only current that comes throught the ammeter is that used to drive accessories if alternator is not running, or that used to recharge the battery after starting.

Jump starting your car with everything turned on before you start will have that current coming through it, but most people turn off the lights, stereo, AC etc when they connect the jumper leads.

The starter does NOT go through the ammeter.

Jeremy, as your wiring is custom, you need to connect everything but the battery and the big cable to the starter to the alternator.

Ammeter goes between this point and the battery. If you are worried then just join them together, as is already done.

If you want you can fit a bigger shunt (a peice of wire) in parallel with the ammeter. (ammeters do not actually read current they measure voltage drop (millivolts) across a piece of wire). Your instrument guy can change your 40A alternator to 100A very easily.

Remember the ammeter only records current entering and leaving the battery, it does NOT indicate how much current your car is using.

The only advantage of the ammeter over the voltmeter is:

A voltmeter indicates if the voltage is above 14V it does not actually tell you if the battery is being charged, ammeters actually tell you if the battery is being slowly discharged. For example if you have a bad connection on the alternator or battery the voltmeter will not show this up. Plus if the battery as an internal problem the ammeter will show constant charging.

If you want to turn your ammeter into a voltmeter it is also quite simple, you can still use it as a centre zero and just place a resistor in series with it to read 14V at say the 20A positive. (As I said the ammeter is actually a voltmeter) You will then need to put the + from the battery onto the Alternator side of the ammeter and ground on the battery side of the ammeter. Once again very easy for your instrument fellow to do.

Oil guauges are also a thing of the past, so do not forget to remove that one too.

Warren

Edited by user Sunday, 20 December 2009 9:19:31 PM(UTC)  | Reason: Not specified

Team

Just back from Premier Instruments.

Good news is the tacho is now fine and the temp/oil pressure guages are reading accurately.

Done in 2 hours whilst I was Chrissy shopping with the rest of Canberra.

The ammeter/voltmeter thing had him stumped though.

He tried following Warrens instructions with a 10k(or something else electronic) resister and it didnt read right.

Arms then went up in the air.

Can anyone size the correct resister for him, or (more likely) steer me to someone who could get it working?

Based on advice from everyone - mainly because the thing is now fuel injected, I reckon Ill get it converted and use 20amps as 14V and -20amps as 10V (thanks Warren) and then Ill know what the batterys doing.

Maybe one day get a faceplate made up for it......

Project 745698.... :)

PS - anyone got a spare ammeter/fuel guage unit I could buy to experiment on??

Cheers

Jeremy

The G will roll again....

Here is a site that explains how to change your ammeter to voltmeter

http://images.google.com...DN%26start%3D42%26um%3D1

This is an external 60A shunt, so this is placed in parallel with the ammeter and carries all the current, it will give you an idea on what you are looking for insid ethe ammeter

http://images.google.com...N%26start%3D126%26um%3D1

If you find yours and cut it, then place tis in parallel , ie batery to alternator, your ammeter will now be a 100A unit

http://images.google.com...N%26start%3D126%26um%3D1

I doubt you will burn that out.

Warren

I seem to remember that the usual drama with Valiant ammeters was that they often had a partial short to earth internally, giving the results that Jim described.

Ive bypassed many Valiant ammeters for this reason alone, often after roadside breakdowns.

I agree with Warren that the 40 amp unit in the HK/T/G GTS dash will be fine because it only measures the current entering or leaving the battery & is not measuring the current draw of all the equipment in the car.

Dr Terry.

_______________________________________
There are only 3 types of people in the world.
1. Those who make things happen.
2. Those who watch things happen.
3. Those who wonder what happened.

Not certain if anyone made a mention of this but here goes.
Any wire run from the alternator back to the ammeter must not have any splicing or joins the same with all your bolted connections they must at least have a spring washer and done up tight.
Also dont forget to cut off and splice your earthwire on the back of the ignition switch as the earth now becomes your temp and oil gauge switch. This is why there is no insulators on the senders for gauges. With idiot lights the earth is connected in the back of the ignition and is dark green in colour
The achilles heal in all of this is your coil wire with the steel tracer. these two can carry a ballast of 30000 volts and are meant for coils without resistors. Modern electrics especially electronic carry between 50-70000 volts through the coil wire making mince meat out of your original yellow one. Many cars have caught alight in this particular area after a let's say an msd6al electronic module was fitted to the car.
Hope you can find something of help. all the best

Any wire run from the alternator back to the ammeter must not have any splicing or joins the same with all your bolted connections they must at least have a spring washer and done up tight.

Not sure about this comment. The original wiring of an ammeter is:

Wire from alternator to terminal "a".
Wire from Battery to terminal "b".
Wire from fuse box to terminal "a"

So the fuse box is directly connected tot he alternator or alternator wire. So splicing it to the alternator wire would be the same.

What you must do is if you have driving lights etc connected to a fuse and then to battery terminal, these need to be removed from the battery terminal and placed ONTO the alternator terminal or spliced into the alternator wire.

When converting to ammeter you must remove the wire from the battery to the alternator, otherwise there will be a parallel path and the ammeter will read discharge. (had this on an HQ GTS that I drove for a fellow, was worried about the alternator during the drive and when we stopped did not turn it off, when we got there I discovered the non ammeter positive lead).

All electrical connections must be tight.

Warren

The best part about being wrong is the pleasure it brings to others.

quote:

---

Originally posted by Warren Turnbull
Any wire run from the alternator back to the ammeter must not have any splicing or joins the same with all your bolted connections they must at least have a spring washer and done up tight.

Not sure about this comment. The original wiring of an ammeter is:

Wire from alternator to terminal "a".
Wire from Battery to terminal "b".
Wire from fuse box to terminal "a"

So the fuse box is directly connected tot he alternator or alternator wire. So splicing it to the alternator wire would be the same.

What you must do is if you have driving lights etc connected to a fuse and then to battery terminal, these need to be removed from the battery terminal and placed ONTO the alternator terminal or spliced into the alternator wire.

When converting to ammeter you must remove the wire from the battery to the alternator, otherwise there will be a parallel path and the ammeter will read discharge. (had this on an HQ GTS that I drove for a fellow, was worried about the alternator during the drive and when we stopped did not turn it off, when we got there I discovered the non ammeter positive lead).

All electrical connections must be tight.

Warren

The best part about being wrong is the pleasure it brings to others.

---

Please do not run a wire straight from your battery to the ammeter. Positive battery runs down to the starter motor, fusible linked wire then runs from solenoid on starter to ammeter B terminal
Then the terminal marked G Has two wires, one straight to the alternator and the other goes to the spliced junction carrying your fusebox,ignition and lightswitch wires. This soldered block splice is insulated with tar dipped asbestos tape and all the wires are red and severe duty gauge. The reason for the gauge is not for normal running conditions, rather for when you first hit ignition and crank the engine. Thanks for the info on the lights Warren, currently I'm running a wire from the starter with a fuse and a relay which in turn is spliced into my lighting loom. I could'nt splice onto the battery terminals as these are the original spring ring type clamps without the red wire coming from the positive. I did find there is a delay when hitting the high beams any ideas on this?

Yes they run originally from the starter with the fusable link. Non Ammeter cars also run from the starter, with fusable link, to fuse box. I just meant from the battery supply.

The only reason I can think of the delay on light is the springs in the dip switch are wearing out, or mechanism jamming ad not throwing the contacts over quickly enough.

Cannot explain why the ammeter burnt out John, as the only curent through the ammeter is bateery charge and discharge current.

Warren

The best part about being wrong is the pleasure it brings to others.