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MG MGB Technical - Aldon Ignitor...what to do.

Evening all,

74 BGT BRG

Aldon 101BR2

Been stuck under the bonnet of the car in the rain trying to figure out why she wont fire......and I think I've eventually narrowed it down to the ignitor unit in my Aldon Dizzy.

This was a fit and forget installation about 15 months ago and up to now I've been very happy, she always starts first time.

I've got the dizzy off and done some tests with thte multimeter and am getting no variation in resistance as I turn the rotor arm it's always down at low resistance, which might also explain way my coil didn't heat up when the ignition was left on.

Now its the Silverstone meet next week so I need to get back on the road ASAP, and I read on the forum that you can just whip out the ignitor and put in points (noting that I brougth the dizzy with the ignitor fitted) but looking at it the ingnitor looks rivited on I was wondering if I could just drill these out and use the holes as my points mount. Also would I need a condenser? To be home I cant remember the old set up too well (with my memory I'm not suprised).

I'm going to write to Aldon as I here there's a 18 months warranty on these things, but I'll need to dig out my paper work. Only problem is I don't have time to wait for them to repair it....... what to do..........so don't want to miss silverstone.


Thanks
c smith

Measure the Resistance again and it is at 1080 ohm constantly through the rotation..... not sure what that means?
c smith

I am back on points and condeser (allways necessary with points) since 8 weeks, as the ignitor broke down as it was not heat resistant enough and collapsed due to overheating.

As i do not know the specs of your engine i can only talk about my experience. With a stock engine i got best results with the dizzy from a 1275 Mini/MG 1300 (ported vac) that i have had in my garage after selling my last Mini many years ago.
Maybe this is one way that will help to keep your car on the road until Adlon can deliver an exchange.
This type of 25D dizzy is offered at very low prices at brakers yards.

Ralph
Ralph

Have you checked for sparks at the coil as well as at the plugs?

Also, it is worth connecting a test lamp across the coil terminals to see if it flashes as the engine rotates.
Dave O'Neill 2

Be very careful with the HT on the electronic system. When it works it has lot more energy than the old mechanical points. I did have a Pirahna but the power end of it failed (high speed misfire)I am back on points and condensor but even here the Chinese found a way to screw it up with poorly crimped caps. The 25D from a 1275 Mini looks interesting, thanks for the input.
Stan Best

Looking for a warm/cold coil or change in output condition when slowly turning the rotor may not be helpful, only the oldest and most basic triggers (like the original Opus 45DE4 distibutors which used the same methodology as points, more modern systems often only send a very brief pulse at the appropriate time). But *low* resistance all the time should mean that current is flowing all the time through the coil, in which case it *should* get warm.

With the trigger disconnected from the coil, tap an earth/ground on the coil -ve terminal (that's assuming 12v is connected to the coil +ve!). You should get a significant spark at the -ve when you remove the earth wire, and this *should* generate an HT pulse. However without a condenser it will be weak, but if you conenct a plug to the coil lead and lay the plug on the block it should still be enough to jump the plug gap. If so, it's the Igniter, junk it and go back to points. 15 months? I've had the same points on my roadster and V8 for about 5 years each now, thats over 10k miles each, and the roadster is still within 1 degree of the spec dwell. I've never had points or condenser fail in service in 40 years, but 3 or 4 years with an electronic pump saw it playing up intermittently. I replaced it with a refurbished point pump and had no problems since.

I assume you have checked for 12v at the coil +ve, and -ve when the wires are removed from the -ve. Check there is still voltage on the +ve when there is an earth on the -ve, 12v in the case of a chrome bumper, 6v for a rubber bumper.
Paul Hunt 2

Guys, I just replaced one for a friend who was having similar problems. Seems the unit was installed without enough slack in the wires inside the dizzy to allow for the vacuum and mechanical advances and they eventually started to break and then arc until one finally broke completely. Barc
Barc Cunningham

Barc makes a good point. The points wire and particularly the ground wire are super flexible to cope with the twisting of the points plate, but the points wire can still experience breakages of the conductors inside the insulation. Who knows what the Aldon wire is like?

Also the constant 1080 ohms constant through the rotation of the rotor must be considered as a 'high' resistance, way too high to trigger the coil. When measuring resistance of electronic components the direction of current flow from the ohm-meter usually makes a difference to the reading, showing high WHEN connected one way round and low the other. Generally the -ve i.e. black probe of the meter carries the +ve potential and vice-versa, i.e. opposite to what you might think.
Paul Hunt 2

This thread was discussed between 13/06/2007 and 15/06/2007

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