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Burning up Vans Engine Gauges - Part Two.

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JakeTheBosun

Joined: 09 Jun 2009
Posts: 10
Location: Whitehorse, Yukon

Posted: Wed Jun 10, 2009 3:24 pm Post subject: Burning up Vans Engine Gauges - Part Two.

Well I'm stumped....my simple RV8, basic analog instruments only, Nipon Denso 40 amp Alternator, Oddeysey battery, worked well for 200 hours.



Saturday Volt Meter burned (resistor on circuit board overheated and melted case), then Oil Temperature gauge did same thing, now today while testing Manifold Pressure full of smoke.



I have;

-checked - no loose wires found ground or power.

-Good Battery-engine-ground (heavy cable, short runs, tight connections.)

-Good bus connections (one central ground bus located at firewall)

-14.2 Volts on meter at gauges while running, but instruments overheat.

-12+ volts on meter when engine stopped, instruments seem not to overheat.

-Removed alternator and took to shop for evaluation....tested on stand and found good output and diodes.

Anybody got a next step?  Nice weather........need to fly

George

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Jake

mprather(at)spro.net
Guest

Posted: Wed Jun 10, 2009 4:09 pm Post subject: Burning up Vans Engine Gauges - Part Two.

Interesting..



Can you see what in the instrument is fried?  Is it a component connected

to the V+ or from the signal/sensor (or something else)?



I assume the 14.2V value is measured on the instrument supply (V+)

terminal.  Can you compare this with the voltage at the bus.



Can you measure the voltage drop between the instrument (display) ground

and the engine ground (with the engine running)?  I understand that all of

the connections appear solid.



Have you done any recent maintenance or mods?

Regards,



Matt-



 	  Quote: 	
		   

 <george(at)yukonflying.com>



 Well I'm stumped....my simple RV8, basic analog instruments only, Nipon

 Denso 40 amp Alternator, Oddeysey battery, worked well for 200 hours.



 Saturday Volt Meter burned (resistor on circuit board overheated and

 melted case), then Oil Temperature gauge did same thing, now today while

 testing Manifold Pressure full of smoke.



 I have;

 -checked - no loose wires found ground or power.

 -Good Battery-engine-ground (heavy cable, short runs, tight connections.)

 -Good bus connections (one central ground bus located at firewall)

 -14.2 Volts on meter at gauges while running, but instruments overheat.

 -12+ volts on meter when engine stopped, instruments seem not to overheat.

 -Removed alternator and took to shop for evaluation....tested on stand and

 found good output and diodes.

 Anybody got a next step?  Nice weather........need to fly

 George



 --------

 Jake





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 47617#247617

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n801bh(at)NetZero.com
Guest

Posted: Wed Jun 10, 2009 4:13 pm Post subject: Burning up Vans Engine Gauges - Part Two.

This is really strange for sure.. The only common denominator is all gauges burning out are engine gauges, your nav lights landing light and all other bulbs. radios etc, seem ok... My .02 cents goes to a bad ground going to the engine from the airframe 

do not archive

Ben Haas

N801BH

www.haaspowerair.com



--------

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user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Thu Jun 11, 2009 6:14 am Post subject: Re: Burning up Vans Engine Gauges - Part Two.

Jake,

What is the ambient temperature around your gauges?  That could be a factor.  The most likely cause of failure to a voltmeter is excessively high voltage.  AC voltage applied to some instruments designed for DC could also cause damage.  But you had the diodes checked out.  And an AC component would be noticed in your headset.  Since you are not having problems with other electrical devices on your airplane, it is unlikely that the aircraft electrical system is causing failure of your instruments unless there is something unique about the power being applied to the instruments.

   I suggest that you replace the analog voltmeter with a digital one.  A high quality digital voltmeter should be immune to whatever your electrical system throws at it.  If after flying with the new digital meter and observing the voltage, the other instruments can be replaced.

Joe

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Joe Gores

JakeTheBosun

Joined: 09 Jun 2009
Posts: 10
Location: Whitehorse, Yukon

Posted: Thu Jun 11, 2009 7:28 pm Post subject: Re: Burning up Vans Engine Gauges - Part Two.

 	  mprather(at)spro.net wrote: 	
		  Interesting..



Can you see what in the instrument is fried?  Is it a component connected

to the V+ or from the signal/sensor (or something else)? 



The resistor on +ve Voltage into instrument burned



I assume the 14.2V value is measured on the instrument supply (V+)

terminal.  Can you compare this with the voltage at the bus.



Yes, was same.



Can you measure the voltage drop between the instrument (display) ground

and the engine ground (with the engine running)?  I understand that all of

the connections appear solid.



I will do this.  I think it was same.



Have you done any recent maintenance or mods?



No



Thanks for taking time to answer..



Regards,



Matt-



 	  Quote: 	
		   

 <george>



 Well I'm stumped....my simple RV8, basic analog instruments only, Nipon

 Denso 40 amp Alternator, Oddeysey battery, worked well for 200 hours.



 Saturday Volt Meter burned (resistor on circuit board overheated and

 melted case), then Oil Temperature gauge did same thing, now today while

 testing Manifold Pressure full of smoke.



 I have;

 -checked - no loose wires found ground or power.

 -Good Battery-engine-ground (heavy cable, short runs, tight connections.)

 -Good bus connections (one central ground bus located at firewall)

 -14.2 Volts on meter at gauges while running, but instruments overheat.

 -12+ volts on meter when engine stopped, instruments seem not to overheat.

 -Removed alternator and took to shop for evaluation....tested on stand and

 found good output and diodes.

 Anybody got a next step?  Nice weather........need to fly

 George



 --------

 Jake





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 47617#247617

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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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_________________
Jake

JakeTheBosun

Joined: 09 Jun 2009
Posts: 10
Location: Whitehorse, Yukon

Posted: Thu Jun 11, 2009 7:47 pm Post subject: Re: Burning up Vans Engine Gauges - Part Two.

Just an update ...thanks to those who answered;



I have performed no modifications except annual inspection and wash.



The instruments burn up the resistor on the +ve supply into the circuit board inside instruments.  The 14.2 V is at instrument.  Fooling around measuring power to ground at many places seems very consistent.



The ambient temperature is not too high (especially compared to you guys in Southern US).



On osciloscope today, we found .004 V AC in the alternator current.  This seems pretty low to me?



Nothing else currently having problems.



Today we also removed the battery -ve cable cleaned it and put it to engine where we connected the cable to the firewall ground post.  All cables are # 2 and about 18" long.



I did notice the negative post on the battery moves just ever so slightly as I tightened the post back on, not very much just enough to notice.



I also see the alternator is spinning at top of the rated RPM, but easily within the 10% the alternator shop taked of.



Thanks again you guys.

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Jake

rampil

Joined: 04 May 2007
Posts: 870

Posted: Sat Jun 13, 2009 9:27 am Post subject: Re: Burning up Vans Engine Gauges - Part Two.

The description you provided sounds like what would occur when a

much higher than spec'ed voltage was applied to your engine

instruments, not thousands of volts but hundreds (at extreme

voltages most resistors would vaporize) and long enough for some heat to

be transmitted to the plastic case.



This does not sound like a ground problem since a poor ground

would REDUCE the current through the resistor.



Are these gauges lit?  Is the light still ok? is it drive from the same

bus or through some type of dimmer?



Ira

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Ira N224XS

JakeTheBosun

Joined: 09 Jun 2009
Posts: 10
Location: Whitehorse, Yukon

Posted: Mon Jun 15, 2009 6:11 pm Post subject: Re: Burning up Vans Engine Gauges - Part Two.

IRA



Thanks for reply....gauges are lit, but I kept the power and grounds for them completely separate so I could eliminate them if problems developed. (I hate cabin lighting in a VFR ship.)  Tomorrow I will check lights dimmers and grounds as you suggest.



Today I find that when I transmit on VHF the manifold pressure drops to "zero", then returns when PTT released.  I recall it has done that before...tomorrow I will see if something is wrong there.  (Radio has separate power and ground bus too....mabe PPP ?)



Thanks again.....appreciate any and all suggestions!

Jake

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Jake

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