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Another cooling fan question

gblwy

Well Known Member
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
 
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.
 
So next time we try to switch on the avionics with the master switch off? Everything should come to life?
 
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.
 
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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