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By robert79
#1610790
Our Garmin 430w has just failed for the second time in 18 months. Symptoms are identical to last time, Nav1 CB popping, which turned out t be a burnt out voltage regulator on the 430 power module.
This is the 3rd failure in 6 years (first failure was different) and it's off got another £1k + VAT repair.

We don't have an avionics master switch and I'm wondering if this is exposing the 430 to nasties during engine start up and shutdown leading to premature failure of the power management components?
The 430 is of course switch off during start up and shut down but so far as I'm aware there is power to the unit the whole time the master switch is on.

The installation manual makes no mention of an avionics master switch as a requirement, but would it electrically isolating it for transient voltages during start up and shut down help avoid a repetition in the future?
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By PaulSS
#1610854
The 430 is of course switch off during start up and shut down but so far as I'm aware there is power to the unit the whole time the master switch is on.


If the unit is switched off then it is off and it doesn't matter what the wigglies are doing before they hit the on/off switch. All an avionics switch would do would stop the electricity before it hit the switch but if the switch is off then the current is not going to go to ground, ergo there's nothing flowing through the unit to do any damage. Transient voltage damage may be possible if the unit is left on during engine start etc when current draw is high and voltage can drop but that won't affect your unit if it turned off during that time.

Sometimes these units have an 'always live' wire to help preserve the ROM, internal clock etc but I couldn't find one on the 430 diagram, so I would suspect it just uses an internal (rechargeable) battery to do this. This would rule out in the slim chance of start up voltage snags affecting your unit via the 'always live' connection.

I am certainly no electronics expert but just because 'damaged power' is available at the on/off switch it does not mean that 'damaged power' is going to flow through your 430 and knacker it if the unit power switch is off.
By robert79
#1610897
PaulSS wrote:If the unit is switched off then it is off


I'm not convinced it's as simple as that for the 430, which is what set me down the train of thought "do we need an avionics master switch?"

When you click the knob to the "off" position, the unit doesn't shut down straight away. You get a message warning you that you've turned it off and a countdown timer until it actually turns off. I guess this is to prevent an "oh ****" moment if you accidentally twiddled with the wrong know during an approach, for example.

So it's clear that the "on/off" switch doesn't isolate the 430 from the bus, and as it's the power regulation components that have (we think) failed again it would seem that these parts at least are live and have at least some current flowing whenever the master switch is on. I don't doubt that either relays or solid state devices protect the majority of the circuitry when the unit is "off" but that's not really a great help if the power pack gets fried every 18 months for want of an isolation switch.
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By PaulSS
#1610903
HMmm, yes it is more interesting than when first viewed. I've never used the unit so didn't know it did a countdown till shutoff. Presumably it has an internal timer relay and I can understand that for switching off but how about start up. Is there the same sort of count up?

As the unit has, presumably, it's own CB could you not pull that once you've turned it off and then only reset the CB once the engine is running, just before you want to turn on the 430. This would give you the opportunity to see if your theory works before fitting an avionics switch because the CB would act just as the switch would.
By robert79
#1610956
When you switch it on it boots up and runs through an initialization and self test.
I think the rotary switch isn't an isolation switch, but merely sends a signal to the unit to start up or shut down.

Pulling the CB would work but I'm not sure it's good practice - for one thing it goes against the grain of pre start checks that all CBs are in.

Why the Garmin 430 should be more prone to this failure than other things without an isolation switch (e.g. transponder is similarly switch on and off using logic rather than an isolation switch) I don't know. Design defect, maybe we got a Friday unit or maybe is should have a separate switch to isolate it from the bus.
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By GrahamB
#1610991
FWIW we had a second hand unit fitted in our group Grumman, and it ran faultlessly for seven or eight years before the aircraft was sold.

I've subsequently had one from new in my AA5 for over seven years and never had a glitch.

Seems like you have a duff one, or something else up with your aircraft that the 430 doesn't like.
By Ridders
#1611104
I’ve a 430 and it’s occasionally reset itself, which is easily recognisable as the display contrast needs to be adjusted and the frequencies go back to start of band.
I’m unsure if it’s a power glitch from the supply at shutdown or the button cell inside loosing it.
I’ve taken to always switching off the avionics (audio,430 and transponder) and then turning off the alternator, waiting for the alt warning light and then shutting down, Doing this seems to have reduced the occurrence, I suspect because of no alternator glitches as the engine shuts down .... but I’m getting the button cell replaced next month as well.
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By PeteSpencer
#1611140
Robert: Someone on PPLIR has mentioned the overheating aspect of the 430W: He quotes Garmin as saying that external cooling air is not needed but is recommended.#

I wonder........................

Peter :wink:
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By GrahamB
#1611144
PeteSpencer wrote:Robert: Someone on PPLIR has mentioned the overheating aspect of the 430W: He quotes Garmin as saying that external cooling air is not needed but is recommended.#

I wonder........................

Both the installations I referred to above had/have a cooling fan.
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By PeteSpencer
#1611188
GrahamB wrote:
PeteSpencer wrote:Robert: Someone on PPLIR has mentioned the overheating aspect of the 430W: He quotes Garmin as saying that external cooling air is not needed but is recommended.#

I wonder........................

Both the installations I referred to above had/have a cooling fan.


Graham: Can you PM me details of your cooling system for 430W please?
Did you install it from the start on advice or in response to overheating?

Regards

Peter
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By GrahamB
#1611190
PeteSpencer wrote:Graham: Can you PM me details of your cooling system for 430W please?
Did you install it from the start on advice or in response to overheating?

It was fitted as part of the original installation, I have no more info than that, I'm afraid. All I know is that when I switch it on, I hear a fan start up!

(You are welcome to have a grovel with a torch under my panel at Cranfield tomorrow if you like!)