A

axel howzen

I'm New Here
Sometimes when I turn on the boost pump or key the mike my EFIS or portable GPS turns off. The portable gets its power off the avionics bus. I have a electronics noise filter installed on the avionics bus. What can I do to prevent this? The noise filter is about 15yrs old.
 
Sounds like a voltage drop issue.

Check for good connections on both the supply side, and ground of all connections for the units, and buss.

I may be off base here, but doesnt sound like a noise issue to me.
 
Mike S said:
Sounds like a voltage drop issue.

I may be off base here, but doesnt sound like a noise issue to me.
Click to expand...

I agree... could also be the pump is bad and drawing an excessive amount of current at start up.
 
It does sound likely to be a voltage drop issue. And the fact that it happens with either the fuel pump or radio transmission actually suggests that neither of those is likely the problem in itself, but rather that just turning on a heavy electrical load causes a dropout.

Can you get it to happen by turning on other heavy loads, like landing lights, or pitot heat?

It is possible that an in-line noise filter may have a high enough series resistance to exacerbate a low voltage situation. But no reason to jump to that conclusion quite yet. Could be any of a thousand other things going on.

So anyhow, I'd suggest that you take a more systematic approach to investigate the problem. As a good starting point, see if you can reproduce the problem in a simple and convenient environment, i.e. on the ground with the engine not running. Then, under those conditions, you can continue to characterize and isolate the problem efficiently and safely.

And by the way, running on battery power only (i.e. without the alternator supplying power), any voltage drop issues should be even more apparent, if that is in fact the nature of the problem.
 
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Power problem

Yep agree.

Sounds like either an excessive load is pulling your voltage down (i.e. high current), or your power supply is starting to fail (i.e. it cannot deliver its rated power/voltage/full load current).

Without knowing the specifics, or being there to test stuff, I can only guess. I would suggest however, that power supplies usually just die rather than degrade over time. It is more likely to be a faulty device pulling too much power.

If the fault is limited to the fuel booster pump, I would get the pump motor tested to see if there is a short in one of the windings. This sort of fault is likely to give these types of symptoms. Just an idea. :)
 
How old is your battery?

Has this problem been gradually getting worse? In an A/C electrical system the battery provides power during current spikes until the alternator catches up, this happens rather fast, but an old battery might not be able to compensate for the increase load and let the voltage drop too much.
 
My vote is for either a weak/defective battery or poor power/ground connections at the battery or downstream.

I would also comment on the use of "exacerbate", but I'm old now and I get confused about all the words ending in "bate" and their correct useage... sometimes embarrassing! So, no comment from me on that portion of the thread.
 
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