Ignition Trigger Can Testing, not +12V?

[flon3y]

I recently purchased a 1981 R65LS and I'm in the process of diagnosing some ignition system problems due to intermittent starting. Fuel system checked out and so did air system. 

So far I have tested the dual ignition coil and found improper resistances:
primary spec=.67-.77 ohm
primary measured = 1.7ohm
secondary spec = 3.7-5.3 K ohm
secondary measured = 0 ohm

The Ignition Module seems to check out okay by following the procedure specified on Thunderchild:
thunderchild-design.com/info-v2.html

The question I have is regarding the Ignition Trigger Can. Thunderchild specifies that the voltage should vary between a few millivolts and +12VDC, but I measure it at a few millivolts and +3VDC. The fact that it's alternating and generating a spark makes me believe that that it is functioning properly but the low voltage throws me off. I was hoping one of you more experienced owners could shed some light. I appreciate the help in advance.

[flon3y]

Also I was considering buying the Dyna dual coil from BeemerShop as opposed to the OEM unit. It's far less expensive and appears to be a quality unit, are there any precautions with going this route?

beemershop.com/Merchant5/merchant.mvc?Screen=PROD&Product_Code=DC9-1_DynaBracket

[georgesgiralt]

Hello,
The HES is actually a transistor. As such, the power voltage is irrelevant because it is dependent upon the circuit the transistor is in.
There is another way to check the HES using a 9V battery and a led. The schematics is on this site but I've no time now to search it for you.
This device is useful to have lying around because you can use it for a static check when putting the bean can back on.
I'm very surprised by your secondary finding of 0 Ohm and your coil giving sparks.  But these beast are capable of strange things.
Last but not least, depending on your  ICU, the coil primary resistance is important. Too low and you overload the icu. Too high and the system is not optimal.

[Adrian]

Also I was considering buying the Dyna dual coil from BeemerShop as opposed to the OEM unit. It's far less expensive and appears to be a quality unit, are there any precautions with going this route?

Hi there - I bought the dual coil back in 1996 after the new (3 year old) BMW coil packed up. I rode the bike for about 15 years before it was garaged - so I got a lot of mileage out of it.
.
I've been rebuilding the bike for the last 4 years - nearly finished - and have put the original Dyno coil back on as it was working well before the bike was taken off the road.
.
So although I have replaced much of the electrical equipment - upgraded alternator - diode board - rectifier - the complete Hall Trigger ignition internals - you get the idea - I am taking a chance on this unit - but by and large people report very long life from them.

.

[BPT]

You will hear many not only approve of but actually recommend the Dyna coils for our bikes.  As Georgesgiralt said, you just need to make sure you get the correct one (ohms).

[BPT]

And here is the schematic for the Hall effect sensor.  There is at least one recent thread here on the site where I asked a bunch of questions about these.
One thing to note, several have said that the switch is not a necessary part for testing the sensor

[Bob_Roller]

Here's a spec sheet for the Honeywell 2AV45 .

https://datasheet.octopart.com/2AV54-Honeywell-datasheet-92379.pdf

From the spec sheet, it shows .2-.4 vdc output voltage when activated .

[Barry]

So far I have tested the dual ignition coil and found improper resistances:
primary spec=.67-.77 ohm
primary measured = 1.7ohm
secondary spec = 3.7-5.3 K ohm
secondary measured = 0 ohm

Curious where you got the coil specs from.  I would have expected a dual output coil for electronic ignition of that year to have a primary resistance in the region of 1.5 ohms so your measurement isn't that far out especially given how hard it is to accurately measure very low ohm resistances.  The secondary  spec seems odd too at less than half the value I would expected.   

[Bob_Roller]

What ignition coil do you have ??
Black and gray, or black and red ??
Usually the secondary circuit is 11k-13k ohms for the OEM coils .

[mrclubike]

So far I have tested the dual ignition coil and found improper resistances:
primary spec=.67-.77 ohm
primary measured = 1.7ohm

The Correct resistance for this measurement depends on what coil you have 
The original coil coil should be about 1.5 Ohms
later coils .7 ohms

secondary spec = 3.7-5.3 K ohm
secondary measured = 0 ohm

If "0" ohms is what you measured
That means it is "Shorted"
It would not even begin to spark


If you measured infinite it may spark but not for long
You could also have the scale set wrong on your meter

Another test on the coil is to test continuity between the secondary winding and the mounting tabs
It should read Infinite 

The Ignition Module seems to check out okay by following the procedure specified on Thunderchild:
thunderchild-design.com/info-v2.html

The question I have is regarding the Ignition Trigger Can. Thunderchild specifies that the voltage should vary between a few millivolts and +12VDC, but I measure it at a few millivolts and +3VDC. The fact that it's alternating and generating a spark makes me believe that that it is functioning properly but the low voltage throws me off. I was hoping one of you more experienced owners could shed some light. I appreciate the help in advance.

The trigger when  blocked with a strip of metal  is  outputting battery  negative
So the voltage is relative to what voltage you are testing it with
So if you are using 12 volts to test it
Put a piece of metal in the trigger and leave it there   
 you should see approximately  12 volts between the center pin and the positive pin
If you are swiping the metal thru the trigger you will see a lower value because your volt meter cant respond quick enough 

Dyna's are good coils get a brown 1.5 Ohm it will work with all the BMW  ICU's  old and new

I have tried all 3 different coils from .7 to 3.0 you will not tell any difference
The .7 ohm will just cause more heat in your ignition system and could burn out the early ICU's
 

[flon3y]

Thank you all for the quick responses! The help is appreciated.

I pulled the spec from my Clymers manual that came with the bike.  Now that I re-read it the specs I listed are for 'single coils' which at the time I interpreted as 'one coil per bike' not 'one coil per cyl. Either way my coil is shot with 0 ohms on the secondary.

My current coil is all black with a metallic bracket if that counts as gray.

[mrclubike]

The original coils were very prone to cracking
Sounds like that is what you have

This is how the Dyna mounts with the 90deg bracket
Make sure you do not short the terminals to ground or have them to close to the mounting bolts

[georgesgiralt]

Hello,
If you want to give a rapid trial, go to a car junk yard and search for an European petrol car. They very often have ignition coils with two outputs and primaries suitable for an electronic ignition system because it is the fuel injection computer that does the ignition ... It will cost you a penny or so and you'll have a coil very sturdy and perfect for the job.
It is possible that Asian or American cars use the same setup but I do not know them, so...
And do not look for a too recent car because they tend to use ignition coils into the plug connection like the latest bikes.

[Bob_Roller]

European vehicles that had this coil setup, have long since been recycled into scrap in the US .
From what I've seen of US manufactured vehicles, I have never seen an ignition module like the one that is fitted to our R65's .
The DYNA coil and adapter bracket are a plug and play set of parts .
Almost bulletproof .

[mrclubike]

I think George is refering to the coil not the ICU

When i was trying to use as much GM delco igniton and charging parts that i could
 I tried to use a coil from a GM vehicle with my GM Delco HEI ignition module and it got very warm
It was only .7 ohm primary
It may have worked with a late version OEM Bosch  ICU because they have current limiting built into them
I have not tested it so i can not recommend it

Currently I am using a 3ohm Green Dyna
It works just fine and the current load is low
Remember the coil has so much dwell time to saturate that  low resistance coils just aren't necessary