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B system ign. switch

bobg56

Well Known Member
Has anyone ever had to change out an ignition switch? I had an intermittent fault during run up today, it would stay grounded when turned back on. I gave the switch an aggressive recycle and it the functioned normally but would do it once in a while. I noticed it when I shut down the engine, turning off A first the engine died. The wiring at the modules appears ok, nothing disturbed, I'm about 90% assured its the switch. I'm thinking about opening up the avionics bay and spraying switch with contact cleaner but I'm also thinking about replacing both switches but it don't look easy, appears they are soldered in place.
 
When shut off, ignition switches are actually closed (on). It will not do any good to spray them with contact cleaner because they are already making good contact. Failing closed is an unusual failure mode for switches. An ignition wire shorted to ground is more likely. Check the wires before replacing a switch. Intermittent problems can fool people. If I remember right, there is a splice forward of the firewall. That splice is highly suspect. It is also a good place to do an ohmmeter check of the ignition switches.
 
I have the old D-180 panel and the switches are solderd , I inspected the P leads and they appear fine in the engine compartment, next thing to do is open up avionics bay and look at the wires in there, I'm ordering the switches from Vans now, I'll get two incase A goes bad...not looking forward to the "surgery" that I'll have to do, I like the suggestion of taking the switch apart and removing one terminal at a time.
 
After removing the switch panel, I think I'm going to swap the ignition modules instead for now, if the problem stays with the B switch then I'll replace it...to bad they are soldered in place...Ignition modules are over $900 :eek:
 
It seems its the B module, after swapping the input plugs the problem followed it...btw those connecter plugs are a royal PIA even with using tool, not a fun job...now to spend $1k for a new module:mad:
 
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