Landing Light Blown Fuse

Anthony

Anthony

Touchdown! Greaser!
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Anthony
Went to fix the landing light on my Tiger, assuming it was a blown bulb and after taking apart everything, inspecting the bulb and connections, the last thing I check (of course) was the fuse. Yep, blown 15 Amp fuse. I replaced it and everything was fine. My concern is the reason for the blown fuse? All the other fuses are fine. Any thoughts?
 
If it doesn't blow again, it doesn't matter. They are there because of the unknowns, so knowing why it blew doesn't really matter unless it keeps blowing.

Because of similar experiences, fuses are now the first thing I check. :redface:
 
Reason: Chafing wires in the cowling because the maintenance A&P didn't secure them properly. BTDT.
 
wsuffa said:
Reason: Chafing wires in the cowling because the maintenance A&P didn't secure them properly. BTDT.
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Or torquing the three screws down too tightly that hold the landing light in place. Just talked to my A&P and he indicated the foam ring that acts as a vibration dampener gets old and compresses too much and the two contacts behind the bulb touch the metal baffling behind it. He suggested replacing that so I'm ordering one from Fletchair.

Thanks guys.
 
Anthony said:
Went to fix the landing light on my Tiger, assuming it was a blown bulb and after taking apart everything, inspecting the bulb and connections, the last thing I check (of course) was the fuse. Yep, blown 15 Amp fuse. I replaced it and everything was fine. My concern is the reason for the blown fuse? All the other fuses are fine. Any thoughts?
Click to expand...

If the blown fuse had a clear glass enevelope you can tell a lot by examining it. If the fusible link is pretty much blown away with burn marks on the remaining ends, it's quite likely that there was a short to ground somewhere as this indicates a huge overcurrent. OTOH if the link is mostly there and the remaining portions appear to have sagged towards the outside of the glass, it's likely that the overcurrent was minimal and it could be that the fuse just got old.
 
lancefisher said:
If the blown fuse had a clear glass enevelope you can tell a lot by examining it. If the fusible link is pretty much blown away with burn marks on the remaining ends, it's quite likely that there was a short to ground somewhere as this indicates a huge overcurrent. OTOH if the link is mostly there and the remaining portions appear to have sagged towards the outside of the glass, it's likely that the overcurrent was minimal and it could be that the fuse just got old.
Click to expand...
I had a really old auto fuse that the link just separated from the terminal end. No sign of over-current at all.
 
Dwight B. Van Zanen said:
I had a really old auto fuse that the link just separated from the terminal end. No sign of over-current at all.
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That can happen, vibration can cause them to break. Look at the fuse and you tell if it melted or mechanically broke.

Something to ponder, if you put a fuse in backwards will it suck when it fail?? ;);)

Sometime the the rush of current when you switch on a light will make the fuse blow if the fuse is old and weak. Put in another one and watch it. If it blows again start looking for the cause.
 
A fuse? Even my 69 Cherokee has breakers.
 
Some times fuses just get tired, especially ones with notched elements (probably higher amp ratings than involved here). Current causes heat, heat causes thermal expansion. Every on-off cycle is an additional stress cycle like bending a piece of bailing wire back and forth until it breaks. Notches are stress risers causing increased stress at that location compared to a non-notched element.
 
The AA-5-series has recurring issues with the wire chaffing and foam crushing described above causing blown landing light fuses. Unless you like replacing fuses every time you turn on the landing light switch, if you find the fuse blown, check them out before replacing the fuse.
 
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