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Hi Camilo,

if you look at apprx 5-o-clock position there is a diode symbol next to Hfe.

This is for checking diode - open circuit one way, short circuit the other way.

So a good wire connect should be a short circuit.

Place the RED probe on one end of the wire and the BLACK on the other end and you should get a bleep.

 

You can also do this with in Resistance mode - select 2000 and attach the probes. A good connect should read '0' a bad connection much higher

 

Some things are polarity sensitive - battery volts - Red probe to positive, Black Probe to negative. If you have it the wrong way round, the reading will have a negative symbol in front of it.

 

Have a practice on some corroded connectors etc

 

Roger

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As an example:-

The tank sender is a variable resistor Camilo. By measuring across the sender terminals with the wires disconnected and using the 200 Ohms range on your meter you can check the operation. Because this is a plain resistance the polarity of the meter leads does not matter. You should not use the meter on the resistance range if there is voltage present in the circuit as that could damage the meter or give bad readings, also the fuel gauge at the other end will affect the readings so it is important to disconnect the wires.

(You could also do this measurement at the fuel-gauge end of the wires by disconnecting at the gauge)

With the sender float fully down the resistance should be about 80 Ohms and with it fully up, zero ohms. Your meter will show if the readings at the extremes are correct and that the progression as the float is moved is linear and continuous.

 

The way a multimeter measures resistance is by sending a low D.C. current through the resistance. By Ohms Law the voltage dropped across the resistance is equal to the resistance value times the current (V=IR) so the meter measures that voltage. The voltage will always be directly proportional to the resistance because the current is kept constant, so the reading can be 'scaled' in the meter to give the output directly as Ohms.

(Thats why its important that no other currents are flowing in the circuit at the same time as you are trying to make the measurement).

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Whilst on the title of multimeters,

 

Can I bring everyones attention to the quite excellent article written

by our contributor Paul Down and printed in TR Action, some time back.

It is available on line, thanks to Paul, and for anyone who wants to do anything more

than check a fuse or bulb, with confidence it is a tremendous read.

 

John.

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Hi John

 

Do you have a link? I could not Google it.

 

While I am on. My coil is at least 40 years old, maybe original. Should I replace it, just in case? Are there original type coils for 1959 TR3As?

 

Thanks

Edited by qim
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Hi Camillo,

your lack of knowledge is in-exhaustible :P keep it up.

 

Generally old coils were very well made. If it has lasted 40 odd years then that is a reasonable testament to its quality.

However things do not last forever so it would be wise to carry a spare and familiarise yourself in how to fit it (make sure your tool kit contains the correct tools.

 

Knowing that modern components can be quite awful many people fit he new component immediately and leave the old one as the spare - because they know it works.

 

Contact the Dizzy Doc (Martin Jay) regards a decent coil for your set up.

 

Roger

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Hi Roger. Thanks

 

I do know lots of things... but, unfortunately, not to do with old cars, and rely on the invaluable help of you and other posters in this forum.

 

Now, that I came round to electricity (of which all I know is that if you flick the living-room switch down, the lights come up, and if you flick it up they go out again: Magic!) I thought I would familiarize myself with things like coil and HT leads for which I have been reading, I should be able to use this gadget of mine, the multimeter.

 

But coming back to my earlier post: is it possible to have the original coil (if it is original) refurbished?

 

i will definitely get a new coil and keep it handy in case this one goes off. I already have spare caps and leads.

 

Regards

 

camilo

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One of the things I have found very useful is a set of test leads that have small crocodile clips on the end.

Particularly when checking voltages with the engine running it means you have at least one hand free to hold the meter to stop it vibrating off whatever you have rested it on & disappearing into the bottom of the engine bay.

 

Dave

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Camilo,

 

You said “…all I know is that if you flick the living-room switch down, the lights come up, and if you flick it up they go out again…”

 

Unfortunately even something as simple that is not always the case.

Go to the USA and it’s the other way round.

 

I think they decided on that way after they gained Independence from the UK, just to fool us if we ever tried to come and take the land back.

 

Charlie D.

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Hello Alan,

 

Was the question “How” aimed at my comment “Go to the USA and it’s the other way round.”?

 

What I mean is that in the US Up is on, and down is off.

I think it’s quite a smart idea. Not so much for light switches, but for things like machinery.

If you fall over and accidentally hit a switch the chances are that you will push it down, and so switch off what ever it controlled.

 

The same was true for 1960’s Lucas switches (maybe even later ones.) UP was always ON

 

Charlie D

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Hi again

 

I've been down to the car and the coil is Lucas but I can't see anything else. Also, I went through the Service Manul and it mentions everything except the coil...

 

I have an old photo that show it; see below

 

Does anyone know what the original coil was like?

post-14128-0-86643400-1512397510_thumb.jpg

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Thank you Bob

 

There are Lucas Sport still around but with different colour. But what's with ballasted and non-ballasted? What's the difference?

 

is this any good?

 

https://www.ebay.co.uk/itm/TRIUMPH-TR2-TR3-TR4-TR4A-TR5-TR6-72-LUCAS-12v-IGNITION-COIL-DLB101/282504322718?epid=1550472295&hash=item41c691de9e:g:050AAOSw8gVX9nIQ

 

or this

 

http://www.pertronix.com/prod/ig/flame/coils/40000_volt.aspx

 

These are push-down rather than screw firttings like my current one. Is it easy to convert? I guess it just takes making a new lead with the correct fitting at each end.

Edited by qim
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Hi Camilo,

 

Google;- Bertram Hill, then Technical, then Multimeter.

 

Re your coil - leave well enough alone, very unlikely you will get anything better than you already have, spare in the boot is a good idea, as a

precaution, make sure you test fit your spare, know which way round the LT Connections are, and mark them, so that in a breakdown situaton;-

A) you can swop quickly and fit correctly

and

B) you know that it will work satisfactorily.

 

John.

Edited by john
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Hi Camilo,

Your car should have a non-ballast coil.

The coil is fed with 12V ALL the time. If you were in a cold climate then cranking from cold may drop the battery volts a fair amount.

This would give a weak spark (maybe).

 

So if you have a lower voltage coil (say 8V) and run it through a resistor for normal running (to drop the extra 4V) then it would be happy.

 

Should you start on a cold morning then the resistor is bypassed and the 8V coil gets the full 12V - wow!!!

However because it is cold and cranking slowly the battery volts may drop. So you will be feeding just over 8V to the coil. This should give you a decent spark.

 

Once you let go of the starter button the ballast resistor comes back in and the now 12V system is supplying the correct amount.

 

You don;t need it - don;t go there.

 

Roger

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So if you have a lower voltage coil (say 8V) and run it through a resistor for normal running (to drop the extra 4V) then it would be happy.

 

 

Roger

 

Well, I do have a starting handle! Who needs a starter motor?

Edited by qim
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In my view the best coils are made by Bosch. They turn up on eBay occasionally. I have a red sports coil on my TR3A bought new on eBay for less than a tenner about 5 yrs ago. Red means it needs a ballast resistor. For a stock 12 volt coil you need a Bosch blue coil.

 

Rgds Ian

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You are welcome Alan. Hagarty Insurancce has also published a very useful series of articles by Rob Seigel on various aspects of vintage car electrics. I included them as technical articles on our website (http://www.ovtc.net/technical-articles.html). Links to the original posting are included in all articles. You may find these to be useful as well. Cheers, Mike

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