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Hi Fellow Rotax Owners
I had a problem with my 914 on a Magni M16 not wanting to start.
This occurred after a 2.5hr flight and aircraft standing for about 3 weeks.
The AP attended to it this morning and found that both ignition modules (A & B) [6 pin connector units]are faulty.
My concerns are that BOTH of these units went faulty at the same time.
Secondly, We replaced one of the faulty units (A) with a new one, after which the engine started but cut out when the L mag circuit was selected on the mag switch. When BOTH were selected, the engine ran but seemingly on the one circuit only.
We then replaced the new A module with the old faulty module A again and the engine started but then died shortly afterwards. The AP stated that the faulty module B, got charged whith the new module A in place during the engine running but that now that the faulty module A was installed again, the faulty module B completely discharged and that is why the engine died.

My questions are:
1. Since this is the third 914 in the past 12 months that the AP knows of that had BOTH module A&B going at the same time, is this not a real risk to flight safety as when both units go faulty like this, the engine cuts out. (or does it not?)
2. If it is rather a case of one module having gone faulty a while ago and now the other module also went faulty, how do you as an owner know? (I sincerely doubt this as, is this not the case why circuit A and B are tested separately during the ignition check pre take off.

I am by no means knowledgeable in these things so please pardon my ignorance but these are serious concerns.

Your comments / help is much appreciated.
Thanks in advance
Herman
  • Re: Ignition Modules on 914

    by » 9 years ago


    Listening to others with similar symptoms I think that this issue sounds temperature related and only affects starting. I know of others who have heated their modules with a hair drier and the engine has successfully started. Once started it continues to run as it should. After it has been shut down, it will restart but leave it to cool and you have a non-starter again.

    I have a bit of an interest in this problem and I am hoping to carry out further investigations in the New Year to understand the root cause. The circuit in the ignition module is very simple, two sections drive the coils and one derives the coil supply and manages the ignition inhibit. I suspect that the problem lies in the latter section. It sounds as though the threshold of some component is on the limit when degraded by temperature and ageing. However once the engine is turning quickly the size of the pulses coming from the inductive pick-ups on the flywheel is large enough to overcome the problem.

    Other than understanding the problem there is very little that you can do to remedy it as the modules are potted in their enclosures and therefore unrepairable.

    It would be nice to know that there was an upgrade to the circuit and that Rotax might come to some arrangement with owners suffering from this not uncommon problem.

    Interestingly the problem only seems to affect the later 6 pin socket versions, I suspect that the older 4 pin socket versions have a different circuit. I would like to get my hands on a faulty one of the latter variant to take a look at :-).

  • Re: Ignition Modules on 914

    by » 9 years ago


    HI Kevin
    Many thanks
    If I read you right, the engine will not cut out in flight as the discharge from the inductive pickups is large enough to overcome the problem with the engine spinning fast?

    I'd be happy to let you have one of the faulty units. Please let me know how to get this to you.

    I will try to get replacement modules tomorrow. I am in Johannesburg.
    My engine has only 250 hours on it and its barely 4 years old.
    Hopefully Rotax will work with me as I understand these are really expensive. :(
    Regards
    Herman

  • Re: Ignition Modules on 914

    by » 9 years ago


    Hi Herman,

    My comments were based on what I have heard from others. I would like to make my own measurements on a faulty unit to see what actually happens.

    I suspect that one ignition fails before the other but you are not aware that it has failed since the fully working unit starts the engine and the faulty unit appears to work correctly at normal engine running speeds.

    The only way to know if you have a failing unit would be to start the engine on one ignition alternating to the other ignition on a subsequent start.

    The circuit is relatively simple with only 90 components. Although it is not an inherently fail-safe design, safety is assured by duplication (2 units) and operating procedure (power check on single unit). However it is never good to have undetected failures in any system that is safety critical.

    I would gladly receive any faulty units to look at, they can be posted to:

    Kevin Stewart
    215 Beverston Way
    Plymouth
    PL6 7EQ
    United Kingdom

  • Re: Ignition Modules on 914

    by » 9 years ago


    It has been the starting circuitry and the way the circuit board has been glued suspend inside the module. Rotax is just now coming out with new and improved ignition modules.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


  • Re: Ignition Modules on 914

    by » 9 years ago


    Hi everyone,
    I personally had a similar problem with my 914 and I know of others. It's pretty debated issue between us. First, it is a common problem, and secondly, it is the price of the unit. I found a manufacturer here at home in the Czech Republic, which for many years has produced a special ignition for almost all kinds of engines. And even under far more favorable original price - les than 200 USD. We have adapted connectors and tested on the engine during flight. Engine fires on the first rotation, runs smoother especially at low rpm, and it looks like it has more power (due to the strong spark). If anyone is interested, I will prepare a more detailed information and I will continue ... Just one more important information, it is a battery ignition, requires a power supply!
    I look forward to potential discussing....

    Pavel

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