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Electrickery


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6 replies to this topic

#1 Grizzly

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Posted 07 August 2018 - 08:10 PM

Hello All,

 

It's been a long time since I've been on here, but I have an electrical issue which one of you out there may be able to help me with;

The other day, my car refused to start - Turned the key - Fired, but then nothing - No sparks at all. Humph!

I have an Aldon Ignitor unit fitted in place of the Points & Condensor, which has given me many years of trouble free motoring. Fit & forget, they said.

I did various checks after scouring the 'tinterweb, to no avail. Checked circuits for continuity, swapped out the coil - still no sparks.

I have a very simple setup: Pinto 2 Litre, 3 ohm Coil (No Ballast) and a Bosch Distributor with the (expensive!) Aldon Ignitor inside.

It was suggested/recommended on the 'tinterweb that I disconnect the Tacho (Capri Clocks) from the Neg side of the Coil, whilst doing various checks, so I did.Checks continued and everything pointed to the Aldon Ignitor. I'd checked all the wiring and swapped the coil, so really it couldn't be anything else. So, bit the bullet, new Powerspark Ignitor on order.

So for now I'm temporarily running on Points & Condensor (Thanks Bob). Engine now running - All OK.

Here's the issue.

Stopped the engine to re-connect the Tacho lead back onto the Neg side of the Coil. Turned the key, but engine refused to fire.

Disconnected the Tacho lead from the Neg side of the coil. Turned the key and engine fired up.

Question is; What's going on here? Is there any chance that a fault in the Tacho has fried the Aldon Ignitor, or vice versa?

Does anyone have any experience of a situation like this happening to them?

My concern is that I don't want to fit the new Ignitor unit when it arrives and toast it straight away, without getting to the bottom of this Tacho issue.

I do have another Tacho somewhere - maybe I could try that?

 

Many Thanks & Regards...


Edited by Grizzly, 07 August 2018 - 08:43 PM.

Regards... Grizzly.

#2 Longboarder

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Posted 07 August 2018 - 08:48 PM

The joys of old tech. Coils have a 'ignition on' positive supply and are fired by the points switching the negative. I'm guessing your tacho is the problem or its connecting wire to the coil negative having gone to a constant earth/ground. Quick check is to disconnect it again from the coil and test it. Should be open circuit. If it's an earth the wire may have shorted to earth or the tacho failed.

Long time no see!


Thought for the week.
Forget healthfoods. I need all the preservatives I can get.


#3 Grizzly

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Posted 07 August 2018 - 09:21 PM

Cheers Nigel,
I mightve guessed youd be quick to chip in! 👍
Thanks, Ill do some checks tomorrow and report back.
Yes, I went walkabouts for a while, but back in the fold now. Hope youre keeping well Sir?
Thanks again...
Regards... Grizzly.

#4 Grizzly

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Posted 08 August 2018 - 11:36 AM

:hi:

 

OK. Tacho wire from Neg side of the Coil goes straight to earth. :(

 

I'll need to trace this wire back to the Tacho and also, get the Instrument Cluster out and test the Tacho itself.

I have a spare Tacho, which measures an open circuit, but I don't want to do a straight swap until I've checked this all through.

 

Quandry is; Did the Tacho possibly get fried by the Ignitor, or did the Tacho possibly fry the Ignitor?

Either way, and going forwards, would a fuse offer any protection?

Haynes Manual (Sierra) does refer to a Suppressor, but I may be looking at the wrong diagram?

 

Many Thanks...


Edited by Grizzly, 08 August 2018 - 11:37 AM.

Regards... Grizzly.

#5 IanS

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Posted 08 August 2018 - 08:39 PM

I am guessing that the wire from the coil to the tacho has worn through its insulation at some point.

Try disconnecting from the back of the tacho and again check for shorts, problem with this is often disconnecting a wire moves loom and hides the short so try to move as little as possible when checking.



#6 Grizzly

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Posted 08 August 2018 - 09:39 PM

Understood and thanks Ian. I will progress this as soon as possible, but it won't be until next week now.

Powerspark Ignitor turned up today, but as said, I won't be fitting it until the Tacho issue is resolved.

 

Interestingly, on the back of the packaging, one of the Fitting Instructions states;

‘Then connect the Powerspark BLACK to the (-‘ve or 1) ensuring no other wire is on that same side”
I asked them how I should re-connect the Tacho?

 

They replied;

Try connecting the tacho to the Positive (+'ve) terminal on the coil.
Connecting it to the Negative terminal, will Earth out the coil/kit and prevent the kit from working.

 

Anyone else done it this way?

Strange because the Aldon Ignitor was happy with the Tacho feed coming from the -'ve for many years.

I assume that this would be ok being fed from the +'ve, but I'm getting paranoid now. :sorry: 


Regards... Grizzly.

#7 Longboarder

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Posted 08 August 2018 - 10:42 PM


 

Connecting it to the Negative terminal, will Earth out the coil/kit and prevent the kit from working.

Going back to basics the tacho 'reads' the off/on/off/on of the coil switching. It has to read the side of the coil that is being switched. For the last 40 years it's the negative wire that is almost universally switched. Over the last few years of cars becoming electronic rather than electrical lots has changed but coils are pretty much the same with just the two wires and they have always worked better if the negative is switched. Yours was fine for years with the tacho reading the negative switching of the Aldon.

Wether the wire went to constant earth, the tacho or the Aldon spat the dummy or what fried what, I haven't a clue. The tacho wire didn't used to go to earth because if it had constant live on one pole and constant earth on the other there would be no switching and no spark.

So you are safe to fit the Aldon and drive tacho-less.

Fault find the tacho wire. Carefully pull the plug from the instruments. Does the tacho wire go the earth. Plug back in. Does the tacho wire go to earth. Repeat several times to see if the result is repeatable (to try to get around the problem of disturbing the loom breaks the short circuit.) You should end up with a reasonable idea that it's the wire that's earthing or the tacho that's fried and gone to earth. Then sort it and get a tacho back on the negative of the coil as you always had it.

You might have spoken to the tea boy at Aldon.

Supressor might help radio reception. Fuse won't help anything.


Edited by Longboarder, 08 August 2018 - 10:47 PM.

Thought for the week.
Forget healthfoods. I need all the preservatives I can get.