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Hi All, 

Currently its my Ampmeter playing games with me:

When turning on the ignition, it runs to “-30” and I need to shake it with ignition off to get it back to “0”.

Does it matter which terminal takes brown and which brown/white ?

Do I need ground ?

I do have stabile 12V from the batterie on teh brown when turning the ignition on...

Advise welcome

Cheers

Oliver

 

 

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You don't need a ground (earth) connection on the ammeter Oliver.   If the ammeter shows a full-scale  discharge as soon as you turn the ignition on(without cranking the engine) , there is a fairly major problem somewhere. There is no fuse protection for the circuitry before the ignition switch so you need to sort this as a matter of urgency before something catastrophic happens.  There aren't many things which can do this - the obvious thing to suspect is a short-circuit of course.

I suggest you pull both white wires from the fuse terminal A3 as a start and see whether the discharge disappears.  If it doesn't there may be a short to earth on the wire from the ignition switch either to the fuse box or to the starter push-switch. 

The ammeter connections are important but it sounds as though they are correct, since it is impossible to have a charge into the battery unless the engine is running. 

The ammeter is a very simple device and it is pretty much impossible for it to suddenly become more sensitive, so the 30 Amps must be taken as being real - which means there is a danger for the wiring loom and the ignition switch. 

Edited by RobH
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Hi Rob, 

Thanks for the swift feedback. Would you 100% exclude a defect of the gauge ? I think I will use my workshop meter to confirm the -30 reading ?

Why taking teh white wires from the A3 ? The brown rouings all run to the A1 ?

Cheers

Oliver

 

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The brown wires don't go via the ignition switch Oliver, so if this only happens when you switch on, the drain must be on the output side of that switch.    If it was a problem on the brown wires it would be there all the time. 

Something is making the ammeter deflect - usually when you first switch on the current drawn is just that of the ignition circuit which will be about 4 Amps.   The ammeter is really just a single loop of thick-ish wire and it is pretty difficult to think of any fault  which will increase its sensitivity.  

 

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Hi Bob, just measured Amps between the brown and ground with my Multimeter - so there is no Amps reading.

I would conclude it must be a Ampmeter defect  ? (but I am just a poor  MECHANICAL engineer and hate this electrical stuff :-)

 

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Not sure what you did there  -  an ammeter must be in series with the circuit to read.  You can't put an ammeter between a live point and earth - it has a very low resistance and will draw a large current (or maybe just blow an internal fuse to protect the meter if it is an electronic device). 

Edited by RobH
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So could I connect the Multimeter with Amps reading between the brown an brown/white instead of the Ampmeter ? And if so, should I read the the same value I read on the TR Ampmeter then ?

I am just trying to replace the Ampmeter to confirm the reading and potential short cut yous suspect....

Important information: When disconnecting the Amp meter after getting it to the -30 in connected condition, it remains at this value. It needs slight shaking to get it back to the 0....

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Yes a multimeter on the amps range to replace the ammeter should give the true reading as you say.

If the ammeter needs a shake to get it to zero it has probably been mechanically bent inside, perhaps from being hammered against the end-stop by a high current ?  Again, it is a very simple pointer arrangement inside. Somewhere I have a photo and if I find it I'll post it here. 

 

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This is more or less what it looks like inside, though this isn't from a TR. The coil of thick wire is between the two terminals and sets up a magnetic field proportional to the current and its direction of flow. The needle is connected to a piece of magnetic iron which is attracted one way or the other by the field ( the needle is missing on this one but you can see the pivot pin at the top). 

1433849804_ammeterinside.jpg.cfbd33b9793c4a5ee90b08e50f266991.jpg

Edited by RobH
typo
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It almost certainly is not the ammeter at fault.  you have probably got a short circuit somewhere as Rob says, may be a wire with its insulation rubbed off touching chassis.  I would not bother checking the current with a multimeter, you may well end up destroying it.

Bob.

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Perhaps an easier way to demonstrate the ammeter is reading correctly is to leave the ignition off and just turn the headlights on main beam.  The ammeter should show a discharge of around 10 Amps if you have standard halogen lamps, or a wee bit less if they are BPF. 

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Too much risk to the car playing with a live non fused 12v circuit. I'd find a sparky (auto electrician) over 60 years of age and get them to analyse the problem. 

Each time you think you might have found the issue and turn the ignition on you risk a major short and fire. In my view it isn't a risk worth taking.

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All right, it seems to bee good to spend the night in bed (instead of the garage), read the posts in the moring first before planing further actions :-)

So, I will follow Robs procedure and disconnect the A3 whites - see what happens and then check the routing of the whites from the fuse to the switch and  coil....

(qualified sparkys are difficult to find over here :-(

 

 

Edited by Moliver
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Final finding:

It is the Ammeter!  I took it out and did the same procedure again. It would jump to -30 when turning ignition and light on but when ticking with teh finger it, it jump back to a normal value.

If I would not tick it but start the engine, it would as well be "pulled up" to the normal +15 Ampds steady state value.

On the positive side, I took the input for serious as I did have some electrical issues (and may still have). A short cut however luckily can be excluded....

Will get an exchange Ammeter and hopefully will rectify this issue.

Thanks for everyones input

Cheers

Oliver

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...and here are some more news and recent lessons learned to share: The Ammeter has a small adustment screw on the back with which the needle friction can be adjusted. Playing with this adjustment finally resolved my issue and the gage shows correct readings, now.

 

 

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