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  #1  
Old 07-03-2018, 04:41 PM
gblwy's Avatar
gblwy gblwy is offline
 
Join Date: Jun 2007
Location: Perth, Scotland
Posts: 489
Default Another cooling fan question

We have an original D180 RV12. Today, after a one hour flight in warm (by UK standards) flight at 13 degrees C at 4000 feet we landed, switched everything off and the fans and fuel pump kept running! Eventually we pulled the fuse, and went for lunch. On re-inserting the fuse an hour or so later all was quiet, so we flew back to our base with no further problem.

How could the fans/pump run with the master switch off?

Thanks...Keith
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  #2  
Old 07-03-2018, 05:03 PM
Mich48041 Mich48041 is offline
 
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Location: Riley TWP MI
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One possibility is that the master contactor is sticking closed after power is removed from the coil. It takes a strong magnetic force to pull in a relay or contactor. Once pulled in, very little magnetic force is required to hold a relay pulled in. Many relays have a thin non magnetic material between the armature and core to prevent residual magnetism from holding the relay closed after the coil is de-energized.
A contactor could also stick closed due to mechanical problems.
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  #3  
Old 07-04-2018, 02:24 PM
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gblwy gblwy is offline
 
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So next time we try to switch on the avionics with the master switch off? Everything should come to life?
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  #4  
Old 07-04-2018, 04:35 PM
Mich48041 Mich48041 is offline
 
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Yes, that would be a good test to determine if the master contactor is sticking closed or if the master switch is not opening. Another possibility is that the WHT/ORG wire between the contactor and master switch is shorting to ground.
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  #5  
Old 07-06-2018, 11:47 AM
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gblwy gblwy is offline
 
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Thanks, Joe.

The solenoid is getting very hot, then it sticks when closing everything down. Once it cools down it resets. Unless you have any other bright ideas I will probably have to replace it.

Cheers...Keith
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  #6  
Old 07-06-2018, 12:11 PM
Mich48041 Mich48041 is offline
 
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Keith,
You have the best idea. Replace the contactor.
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