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contactor not contacting!

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mrspudandcompany(at)veriz
Guest

Posted: Sun Mar 10, 2013 2:12 pm Post subject: contactor not contacting!

I have a 1977 Cessna Cardinal, and recently it is  necessary to flip the master on and off several times in order to power up the  panel.  It seems that the master is OK because I can hear the contactor  activating and deactivating as the master is turned on and off.  After  several tries it will finally power up the panel.  Once the contactor has  activated and supplying power, I have never lost power again until physically  turning the master off.  I am making a wild assumption that the problem is  due to a faulty contactor, perhaps corrosion or some kind of crud (technical  term used extensively by electrical engineers) on the contacts.  Is this a  common problem?  Is changing the contactor the right way to fix it?   Comments, suggestions, please!!

  

 Thanks,

  

 Roger

  

  

  

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JLuckey(at)pacbell.net
Guest

Posted: Sun Mar 10, 2013 2:48 pm Post subject: contactor not contacting!

May I suggest a little testing.



 



The next time you turn-on the master and hear it click (or clunk as you case

may be) but the panel does not "power up", take a voltmeter and see if there

is voltage on the load side of the contactor.  If not, then you've got some

form of contact failure.



 



If you have power on the load side then your problem is elsewhere - I'd

start looking for loose connections by putting a wrench on the connections

down stream of the contactor to make sure they are tight.



 



Then report your findings here for more assistance based on your test

results.



 



  _____  



From: owner-aeroelectric-list-server(at)matronics.com

[mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of R. curtis

Sent: Sunday, March 10, 2013 14:11

To: aeroelectric-list(at)matronics.com

Subject: contactor not contacting!



 



I have a 1977 Cessna Cardinal, and recently it is necessary to flip the

master on and off several times in order to power up the panel.  It seems

that the master is OK because I can hear the contactor activating and

deactivating as the master is turned on and off.  After several tries it

will finally power up the panel.  Once the contactor has activated and

supplying power, I have never lost power again until physically turning the

master off.  I am making a wild assumption that the problem is due to a

faulty contactor, perhaps corrosion or some kind of crud (technical term

used extensively by electrical engineers) on the contacts.  Is this a common

problem?  Is changing the contactor the right way to fix it?  Comments,

suggestions, please!!



 



Thanks,



 



Roger



 



 



 



  _____

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mrspudandcompany(at)veriz
Guest

Posted: Sun Mar 10, 2013 3:17 pm Post subject: contactor not contacting!

 	  Quote: 	
		      

      

The next time you    turn-on the master and hear it click (or clunk as you case may be) but the    panel does not “power up”, take a voltmeter and see if there is voltage on the    load side of the contactor.  If not, then you’ve got some form of contact    failure.    	  Quote: 	
		       

There seems to be      no intermittent connections because once it is on it stays on, and the      starter cranks the engine just fine. I'll put a meter on it next time I'm at      the airport, but highly suspect the contactor.     

      

Roger 	
   

    

If you have power on    the load side then your problem is elsewhere – I’d start looking for loose    connections by putting a wrench on the connections down stream of the    contactor to make sure they are  tight.

	
  

I am using the Free version of SPAMfighter.SPAMfighter has removed 342 of my spam emails to date.Do you have a slow PC? Try a free scan!     [quote][b]

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Mar 10, 2013 5:13 pm Post subject: contactor not contacting!

At 05:10 PM 3/10/2013, you wrote:

  	  Quote: 	
		   I have a 1977 Cessna Cardinal, and recently it is necessary to flip the master on and off several times in order to power up the panel.  It seems that the master is OK because I can hear the contactor activating and deactivating as the master is turned on and off.  After several tries it will finally power up the panel.  Once the contactor has activated and supplying power, I have never lost power again until physically turning the master off.  I am making a wild assumption that the problem is due to a faulty contactor, perhaps corrosion or some kind of crud (technical term used extensively by electrical engineers) on the contacts.  Is this a common problem?  Is changing the contactor the right way to fix it?  Comments, suggestions, please!! 	


   Based on the facts (1) you can hear it operate

   whether it connects or not and (2) once connected

   it stays connected is a strong indicator of a

   bad contactor. I believe all the Pawnee Plant

   aircraft went 28v in '78 so your airplane probably

   has the legacy 12v PMB/Stancore/White-Rogers contactor.

   Does it look like this?



   



   If so, you could get a 'test' replacement from

   Newark for about $25. (Cat# 35M2084 which is a

   4-terminal device. You'll have to add your own

   jumper between coil-hot and BAT terminal)If

   that 'cures' the problem, you can go for the

   holy-watered part.



   If it's some other part, post a picture of

   it and we can probably identify it's generic

   roots.



   I'd like to have your failed part to do a tear

   down inspection and report to be posted her

   on the List and archived on the website.



 

 

   Bob . . .    [quote][b]

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mrspudandcompany(at)veriz
Guest

Posted: Tue Mar 12, 2013 8:17 am Post subject: contactor not contacting!

Based on the facts (1) you can hear it operate

  whether it connects or not and (2) once connected

  it stays connected is a strong indicator of a

  bad contactor. I believe all the Pawnee Plant

  aircraft went 28v in '78 so your airplane probably

  has the legacy 12v PMB/Stancore/White-Rogers contactor.

  Does it look like this?



 WHITE RODGERS70-902

<http://www.newark.com/productimages/nio/standard/4298109.jpg>  



  If so, you could get a 'test' replacement from

  Newark for about $25. (Cat# 35M2084 which is a

  4-terminal device. You'll have to add your own

  jumper between coil-hot and BAT terminal)If

  that 'cures' the problem, you can go for the

  holy-watered part.



  If it's some other part, post a picture of

  it and we can probably identify it's generic

  roots.



  I'd like to have your failed part to do a tear

  down inspection and report to be posted her

  on the List and archived on the website.





 

 

Bob,

 

Thanks for the reply.  I have a 3 terminal continuous 

duty 12V contactor that I will put in as soon as the 

weather cooperates for some outdoor maintenance.

 

Will mail the junk contactor to you as soon as it is liberated.

 

Roger



  _____  



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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Mar 12, 2013 9:08 am Post subject: contactor not contacting!

 	  Quote: 	
		  



  	  Quote: 	
		  Bob,[/b]

 [/b]

Thanks for the

reply.  I have a 3 terminal continuous [/b]duty 12V

contactor that I will put in as soon as the [/b]weather

cooperates for some outdoor maintenance.[/b] [/b]

Will mail the

junk contactor to you as soon as it is

liberated.[/b] [/b]



	
	


   Great! I'll tear down, photograph,  analyse and share . . .



 

 

   Bob . . .    [quote][b]

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