Amazon: Hot Coil - Too Hot?

[Carlsson 986]

Ok, so part of the changes on my Amazon have been to take out the old/original coil in favour of a standard type unit, and of course, the addition of an alternator. All was working fine until the regulator gave out causing a spike of unregulated charge to be sent to the battery and the temporary failure of the coil. It became extremely hot to the touch but then cooled down over time and worked although some arcing on the terminals became evident.

In order to ensure that the electrical system started afresh, I have replaced both the alternator and coil. The alternator is now a 65A Delco Remy DRA00882 unit, and the coil with a Lucas DLB 101 unit. This coil is mounted where the Volvo coil used to be, but with the terminals pointing down, the armoured casing has been cut back, supported below the dash, and the cable extended to suit the new coil position. The coil was still however getting rather hot, and is giving me cause for concern about travelling too far in case another failure occurs. So, having read up on coils and their ‘ratings’, I have opted for a new Pertronix Flame Thrower 3.0 ohm coil to see if that cures the issues. It hasn’t it still gets hot but not so much that you can’t touch it– little did I realise that the Lucas unit was also a 3.0 ohm unit, doh!

I have disconnected all of the accessories to leave the system as basic as possible, except for a push start button on the dash which loops two of the ignition switch terminals, and is only live when pushed momentarily. The ignition set up has been checked and checked again – B20A set at 20-21degrees BTDC and 16thou on the points. Battery reads ok on multimeter as does alternator. I have a Smiths 50-0-50 ammeter and this shows a nominal draw on idle but high current draw when lights on of +35-40amps. Bulbs are H4’s from memory, nothing special at 60/55w.

Car goes really well none the less. Is this ‘normal’ or not? Becoming paranoid about things and confidence about going far has been dented – any pointers/answers appreciated of course.

Ric

[Ron Kwas]

Ric;

If those coils are intended to be used with a Ballast resistor and you have not installed one, that would certainly increase the primary current and cause heating.

Headlight current should not be indicated because they are Loads which should be wired on the same side of AMP meter as Alt. Reference "H" diagram (source: http://www.sw-em.com/elecramb.htm ):


Cheers

[swedishandgerman]

I'm away from my geeky file that I store a load of geeky information in, so I'm going from my stupid little memory here but I would say that you've too much current going through that there coil of yours, so it needs, as Ron says, a resistor.

The alternative would be to go for a higher ohm coil, but you're running with points - good man! - and so that would allow for too much current to go through your points leading to premature knackerisation of the points faces.

Personally, I see little benefit of high ohm coils, so I would stick with what you have and include a resistor. Right now, there's too much current going through your coil putting too much draw on your charging system, too much load on your LT circuit, too much current through your points and too much current going through your coil causing it to overheat and will cause it to wear out faster.

BTW, I really like the tidy job you have done there to cover up the hole that the old coil went in. Ordinarily, I would leave as is based on my opinion that the standard Amazon ignition set up is very, very good APART from the inability to change the coil for a better one. A lower ohm coil reduces the current accross the points and modern coils, like yours, have better windings so are more powerful, so do ACTUALLY provide a better spark at the plugs, unlike the debacle that people are lead to believe about distributor upgrades/alternatives.

Thanks - you've made me think about the coil in my old Beetle which isn't starting too well at the moment.

By the way, we spoke a while ago about the condition of your standard distributor. Did you manage to clean it up and work properly?

[swedishandgerman]

Actually, in retrospect a 3 ohm coil should be correct for a non ballast set up which this is, so what I've written above is not correct.

I wonder what effects fitting a resistor to a 3 ohm would be.

I have always found the people at Accuspark extremely knowledgable and helpful on the phone, so you might do well ringing them.

All said, an overheating coil is due tio too much current.....

[Carlsson 986]

Gents, Apologies for not replying sooner but have been trying to get my head around this electrical business.

I have used my trusty Gunson multimeter which I am still learning about, and have checked the voltages being produced. The battery at idle was ok at 12.4V but at increased revs it went up to over 15V which I don't believe is good for it over any sustained period. 15.4V to be exact. I therefore sourced a battery from my local scrappies for £20, that had a full charge and was showing 12.4V again disconnected. This has been fitted but subsequent checks are as before, which makes me suspect the alternator.

Sure 'nuff, the alt is putting out in excess of 15V at idle - photo attached. Don't forget this is a 'new old stock' alternator only recently purchased - does this mean its regulator is not working as it should, or perhaps but unlikely, the multimeter is reading high, which is not so as it appears to record the battery ok. Are there any other checks I can do to verify its performance? Cannot send it back however as I've had to modify the bottom mount to take the 10mm bolt and to get the pulley to sit in line. Would a change to a larger pulley size result in a slower alternator rotation and hence a lesser output?

Ron - many thanks for your ammeter wiring detail and article. I have wired mine directly in series: alt-amp-starter/batt - and it's only showing the positive charging condition from the alt to the battery when powered. It does not show any discharge with ignition and lights on, primarily as you say there is no charging taking place. But why not, surely the discharge current should also be indicated when no charge is taking place? Is the ammeter suspect too I wonder? I have another somewhere so will do a swap to check if poss.

Adam - yes you are also right - too much current in LV circuit, all I think due to the alt output, and no, not really looked at the dizzy again as I want to resolve this issue first, but I will give Accuspark a call. Honest!

Ric

[Ron Kwas]

Ric;

First, verify calibration of your multimeter to assure its readings can be trusted! As a quick check, a brand new 9V Battery should read somewhere around 9.2 to 9.4 Volts.

From your symptoms, Battery is likely fine (but when at 12.4V, down a bit on charge, see linked article), but when raising RPMs (certainly at idle), a 15V Bus voltage is indeed too high, and will result in overcharging, and electrolyte being cooked from Battery!

High Sys V is undoubtedly caused by the Charging System not knowing when to quit (Either a faulty Reg, but more likely, something like a poor chassis connections on Alt or Regulator ...it is also possible for this poor connection to be internal to Alt!...but first, check all connections external to Alt/Reg having to do with Charging System and Battery...a voltage drop on a poor conn can cause Regulator to get pulled up by that Vdrop, adding this voltage to its reference resulting in your symptoms...so clean and tighten all of these connections (and protect with ACZP), then recheck sys voltage at elevated RPMs! If symptoms remain, remove Alt/Reg Assy and have tested at an Auto Elec shop.) Report findings!

Amp meter is not showing Charging current because it is likely not wired as it should (see H diagram)...and with sys V high, I would certainly expect a charging current...double check elec position of Amp meter!

Good Hunting!

[Carlsson 986]

On the ball as usual Ron - with thanks.

Will work through the list and report back.

[CLIVERALLY]

go for poor chassis connection

[swedishandgerman]

I would say you've found the problem there Ric; too many volts causing too much current. I was thinking about this and the non-ballast coil should be the correct one for the set up, so I would say the voltmeter is reading correct and seeing as V=I*R (I is current), you see what I mean: too much current for the coil to cope with and it can't stay cool.

By the way, when the coil overheats too much, there's too much resistance and eventually the output reduces so much there's not enough oomph for the spark to jump at the plug...

Your comment about the size of the pulley on the alternator - no, as follows: The output is regulated by the regulator. When the alternator is stopped or slow, there's no or little output, so the regulator swtiches it to 'off'. This is so that the current doesn't go the other way and drain the battery!

Once at speed, the alternator starts charging and the current goes up and up and up as speed increases. Of course, the system is 12V, so this needs to be regulated to ensure it doesn't cook the battery as well as too much current going through things like the coil (!!) and other motors & bulbs. So when the V reaches something like 14V or so, the regulator switches some of the current away from the system.

The speed of the pulley is irrelevant.

The regulator is letting too much current through, so to speak.

As above, check all the connections in particular the chassis earth strap (right down low by the starter) - but I would say it's a faulty regulator. Is yours a regulator that can be extracted and replaced? Or is it an integral part of the alternator?

[Volvorama]

Did a quick check on the diabolically scruffy 122S estate I bought under the influence of cider. It has original ignition, a dynamo and runs fine. Left it running for a while and the coil barely gets warm.
Incidentally, I help a friend with a '55 PV converted to 12V. Strangely enough the 6V coil doesn't seem to mind running 12V although we've not driven it far. Don't want to chop the old ignition switch about so we may run a 12V coil but use the old ignition circuit to trigger a relay to supply this with the correct feed (that stays on when the starter is turning).