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Yak-52 Gen Fail Indication

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scott.glaser(at)thedefian
Guest

Posted: Thu Mar 13, 2008 1:36 pm Post subject: Yak-52 Gen Fail Indication

High All,



I'm having trouble with a Gen Fail Indication on my '52.  I was running on

the ground in the RPM ranges where the gen should have been on line and the

gen fail light was flickering.  I shut down and checked with my local guru

who warned me of wire chaffing on the voltage regulator damper plate.  I did

find a wire that was on it's way to being chaffed but that didn't seem to be

all the way through the sheath.  I repaired the wire, reconnected the

voltage regulator and ran the engine.  Much to my dismay the gen fail light

is now on all the time.  I checked the reset button on the voltage gadget

box on the firewall above the voltage regulator, it had not been tripped.  I

also opened he circuit box on the right side behind the access panel and saw

no smoking guns.  Any help or suggestions as to what could be the culprit

would be greatly appreciated!



Scott

N8252

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mark.bitterlich(at)navy.m
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Posted: Thu Mar 13, 2008 1:57 pm Post subject: Yak-52 Gen Fail Indication

Contact me at 252-671-7005



Mark Bitterlich

 



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viperdoc(at)mindspring.co
Guest

Posted: Thu Mar 13, 2008 6:45 pm Post subject: Yak-52 Gen Fail Indication

I'm certain by now you have talked to Mark and he has more eloquently said

what I'm about to say. Having gone through exactly this with the help of

Mark and Dennis it was sorted out. First thing to do is ohm out your fuses

in the power panel. Unfortunately on the 52, it is behind your seat! You

need to pull the fuses out of the circuit to check them otherwise all you

are going to do is ohm out your circuit. I found that it was my 30 amp fuse

that was between the main circuit between the BMP 200 and the carbon pile

regulator. Sorry for my generality but my 52 wiring diagram is at the

hanger.

Start with the simple, check your fuses. If you have a need for a spare BMP

200, I have one! :>)

Doc



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mark.bitterlich(at)navy.m
Guest

Posted: Fri Mar 14, 2008 10:54 am Post subject: Yak-52 Gen Fail Indication

Actually Doc, I do not recommend checking fuses right off the bat with a

problem like Scotts.  I am not a big fan of dive-bombing, although your

recommendation to check fuses is of course always a good idea, and each

person likes to do things their own way.  



Personally, in a case like Scotts... And no one really knows the whole

story here since there is more that has happened than is in his original

email... But regardless, I recommend going to the DNP-200 relay and

putting an alligator clip on the bus line going to the generator.  Start

the engine and watch the voltage.  Not only should it be there, but it

should come up to 28 volts and start regulating with increase in engine

RPM.  This is one test... It only requires removing a cover and a panel,

and tells you a LOT.  If you have regulated voltage there, then it is

likely that you have a DNP-200 issue, or a broken wire, etc.  If you

have voltage, the next step is to check the enable terminal on the

DNP-200 (pin V).  If you have NO voltage, you move your alligator clip

right to the generator itself.  Shortly you get to the point where you

check the fuses.  But for example, if you DO have voltage at the

generator bus on the 200, there is simply no need to go yanking fuses to

check... They're obviously good.  



Having worked with Marine Electricians on airplanes for almost the last

4 decades, I can tell you that there are clearly two ways to go about

fixing aircraft electrical issues.  



First Method:  "I saw this problem before, and this is what caused it

last time, ok... Try replacing that part first.  If that does not work,

start replacing one part after another until it does work."  This is

typically the common method and is an example of your tax dollars at

work. 



Second Method:  Look at the system.  Understand how it works.  Take

measurements at critical points until you know what MUST be bad and why

it caused the problem you are seeing.  Pull part and replace it, and

know even before you turn it back on that it is going to work.  

I teach the second method.  The over-whelming desire by most everyone on

this planet is to use the first method.  



Guess which method most general aviation guys typically use?  



Now another warning against the first method.   When you start swapping

out parts, you have the distinct chance of screwing something else up,

and now you have TWO problems on the same system, and that can be deadly

to find.  



Scott started with a flickering generator light.  He was given a

recommendation to pull the voltage regulator out and check for bad

wiring.  He did that.  He saw a wire that needed attention.  He fixed

that wire.  He put the regulator back in.  Now he has a totally dead

generator with a constant generator light.  Hmmmm.   



Mark Bitterlich



 



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brian-1927(at)lloyd.com
Guest

Posted: Fri Mar 14, 2008 12:33 pm Post subject: Yak-52 Gen Fail Indication

On Mar 14, 2008, at 11:50 AM, Bitterlich, Mark G CIV Det Cherry Point,  

MALS-14 64E wrote:



 	  Quote: 	
		   

 Point, MALS-14 64E" <mark.bitterlich(at)navy.mil>



 Actually Doc, I do not recommend checking fuses right off the bat


	


I guess that is what makes a horse race. I do tend to check the  

obvious things first, e.g. fuses and broken wiring. I find that gets  

about 80% of the problems without having to resort to the schematics  

and the multi-meter. But once I get past those obvious thing, I am  

right there with Mark.



Brian Lloyd                         3191 Western Drive

brianl AT lloyd DOT com             Cameron Park, CA 95682

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



PGP key ID:          12095C52A32A1B6C

PGP key fingerprint: 3B1D BA11 4913 3254 B6E0  CC09 1209 5C52 A32A 1B6C

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