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TR 5 ammeter wiring - alternator with internal voltage control


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HI

 

Novice error

the car has been working fine for the last 30 years in my ownership and I have re built ++  but never chaged the wirring loom from when I bought the car in 1989 with an alternator conversion allowing the  voltage control unit to be removed . 

I have removed the Ammeter from the dash board including wires without noting the connection configuration - I had assumed I would replace all following the manual & circuit diagram. Unfortunately, the car has an alternator [Iskra AAK 4598] with an internal voltage control and the original - voltage control-component has been removed from the car ( although there is the remnant of the wire terminations correct to the wiring diagram).

  the wiring diagram in the manual doesn't cover the ammeter  configuration I have -- and neither does my knowledge of alternators . I am sure there will be an article in a TRACTION technicalities on this - that search is beyond me- so is there a Dr Bingley equivalent for alternator circuitry out there that can give me some direction             

I have 5 wires removed from the ammeter

 

Brown- white from alternator B+ attached to Brown from ignition switch – as per circuit diagram

 

 Brown – white from the other alternator B+  - not on circuit diagram -   what does this do and where dos it attach to the ammeter

 

 

2 brown wires ( separate) that are joined at and connect to the +ve battery terminal ( seem to parallel each other for no specific purpose ??? duplicate?)  the circuit diagram has only 1 wire shown for this connection and I can’t work out what the purpose of the other is -. Both go from ammeter into the loom and remerge in the engine bay  for connection to the battery

 

From the position of the wires once removed suggests all the Brown – white wires go to one terminal of the ammeter and the brown wires to the other terminal ? is this correct

 

Have you got a circuit diagram for a TR 5 right hand drive using an internal voltage control or advise on the correct wiring for returning ammeter to service ?

 

Any help welcome – particularly working out the hieroglyphics on the Alternator  

 

Cheers

john 

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It looks like the ISKRA is similar to a Lucas ACR and the two B+ terminals are in parallel.  I expect both sets of wires are doubled-up to increase the current capacity, instead of using a single heavier wire.

The two brown/white wires along with the brown to the ignition switch, go to one terminal on the ammeter and the brown wires to the battery go to the other terminal. 

Viewed on the back of the gauge the alternator usually goes to the left hand terminal and the battery to the right hand one.  

 

 

 

 

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RobH 

thanks for the prompt response 

that seems to stack up although the brown- white wires appear to have been attached to the other side  -ve scale end of the ammeter natural location position relative to dash board- I guess it makes little difference as the ammeter with a central '0' is not directional 

your reply also clarifies the 2 brown -white connection to alternator. I was working on one bringing the charge generated out and the other suppling the stationary exciter winding feed.

apologies more inquisitive question as I am now curious    

where/how does the alternator static windings get feed ? not obvious on my google enquires !!

the alternator is earthed through its case and mountings to the engine ?

Why does the ( all?) alternators have other terminals the labelled same as the plug/terminal ?

finally is there an easy way to tell if the ammeter is shagged  broken ? 

 

regards

 

John 

  

 

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An alternator has the moving rotor 'excited' and the main output coils static, which is the opposite to a dynamo where the field coils are the static part and the rotating armature and commutator carry the output current.  

The feed to the alternator rotor is internal for a machine with the regulator inside. There are a separate set of three diodes specifically for that and a slip-ring connection to the winding on the rotor.  The regulator varies the current to the rotor in similar fashion to the field connection on a dynamo.

Yes the earth connection is made through the mountings.

This is the general arrangement for the lucas type:

alt.jpg.a00c1fd4f240eaaa8ec695dd4315f7f8.jpg

There isn't really much you can do to test an alternator other than to look at the output voltage. The manufacturer will specify an output voltage range at a given speed, but it should be about 14 Volts at (say) 3000rpm engine speed.

The best diagnostic tool is your ammeter.  When you start the car you should see an initial high charging current which then drops over the space of a few of minutes towards zero - the actual time taken will depend on the charge state of the battery.  If you don't see that high current the alternator may be faulty. If it doesn't reduce towards zero the battery may be dying. 

 

Edited by RobH
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again many thanks for the clarity and deconflicting dynamo alternator configurations very useful.

 

I am confident to rewire ammeter and record connection for future. the alternator is ok as I had the local alternator garage check it out.

 

Do you have any simple tests for the ammeter? and  if this isn't working what would be the impact on car charging would stop I assume?

 

thanks 

 

John 

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There is very little that can go wrong with the ammeter John - basically it is just a single-turn loop of thick wire between the terminals  and an iron pointer which is moved by the magnetic field set up by the current flow.  It has been known for the wire to come unsoldered in which case it stops working, which should be obvious, and the battery won't get charged. I believe that failure is rare.  (There was a case discussed not long ago on here).

A simple test is to leave the ignition off and turn on the headlights. The ammeter should register a 10Amp discharge if you have standard headlights. 

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I cannot comment on TR5 fitment, but James Christie and I published an article in TR Action 248 (March 2011) about fitting a Moss kit to his sidescreen TR.

The article can be viewed on-line on the Register's website, or, if you PM me with your email address, I can send you the article in MS Word.

Although James kept his ammeter, as did I when I changed to alternator in 1993, the article includes information on circuitry for use of voltmeter.

Ian Cornish

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