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Magic smoke escaped

Capt

Well Known Member
Okay that magic smoke from my Cessna type split rocker master switch decided to escape during start, the result? All my "EI" engine instruments are dead! Everything else elect works inc starting, spent hours chasing the fault to no avail, might be time to take up sailing! -:(
It's a birds nest under my dash (I didn't build the beast). All guages have circuit breakers, none popped, wish I could crawl under my panel, 6ft 220 lbs at my advanced age means I'd never get up again! There must be a hidden inline fuse/s somewhere buried, trouble is if I find same what was the original reason why it/they blew? Switch appears fine (I Pulled it apart) That's the million dollar question! No Xmas flying for me....sob sob sob
 
Unfortunately, my only recommendation is to start tracing every wire and create a schematic. It's a royal PITA. But having an accurate schematic is a necessity in my opinion. It will also help the resale value.

Start by pulling your EI gear and testing the voltage on the power pin. Then trace that back to the power source.

I may be older and I am a pound or two heavier. I've spent more time under my panel that I care to admit troubleshooting an issue with my GTN650 that turned out to be an error in the install manual. (the manual error has been fixed) At least with my RV-10, if I pull the front seat and stick, I can lie relatively flat.

One last piece of advice, since most of us old farts need bifocals, get a a pair of glasses that has your reading prescription on the entire lens. You will be looking out of the top of your glasses a lot. :D
 
Motherhood warning

For those of you who do not have a schematic for your plane, I would recommend you do it now, before something smokes or something breaks in the field. Once the schematic is done, make sure it is what you want. Otherwise you are trusting in blind luck some idiot didnt wire your panel.

Sorry for the motherhood statement.
 
Great opportunity to pull the panel along with the wiring and just start over. When you do establish some objectives:
- You end up with full documentation of what wire is on what connector. I find this a superior method to wire labels.
- Design the panel to come out. NEVER crawl under the panel.
- Dump the 1960 Cessna split rocker switch. Why this lingers amazes me.
- If you have your running list of panel upgrades now is the time. A new panel is just a ~$25 piece of aluminum from Van?s, some time cutting holes and paint.

When you are done you have ?your? panel and you know everything there is to know about it.

Carl
 
Unfortunately, my only recommendation is to start tracing every wire and create a schematic. It's a royal PITA. But having an accurate schematic is a necessity in my opinion. It will also help the resale value.

Start by pulling your EI gear and testing the voltage on the power pin. Then trace that back to the power source.

.....

That is the short term answer to get you flying again.

Don't forget to check the grounds and look for wires rubbing on sharp edges that can cause a short in the middle of a bundle.

As Bob says, just trace it out with a voltmeter, cut open the tyraps if you have to, as you follow wires. You know(?) the switch has power, and you then need to see if it gets to the EI unit (probably not).
 
The only thing the Split Master should control is your Master Relay and ALT Field.

If everything else works as you say, Starter, Radios, Lights, Flaps, etc.... I would suspect that the builder wired all of the EI gauges to one breaker or fuse and that gives you a place to start.

The fact that the Split Master "smoked" doesn't make sense to me that you would only lose a portion of what the Master Relay feeds. Something is amiss.

This is assuming the builder wired the Split Master as it should be, and did not take a sort cut and use it to control other loads, like the EI stuff. That wouldn't be good practice.
 
The only thing the Split Master should control is your Master Relay and ALT Field.
Correct me if I'm wrong, but doesn't the BAT half control the master and the ALT half control the alternator field (through a circuit breaker)? Maybe I'm misunderstanding what you wrote.
 
Guys I typed a huge lengthy response but lost the lot!....grrrrr
Anyway thanks for the replies, it's still ongoing, shall keep you lot informed, can't re write the million things I've done thus far again, time for a drink
Merry Xmas, stay safe up there:)
 
Okay guys shall type what I lost yesterday.
Again thanks for the replies.

This bird is 1225lbs empty!
The previous owner was an ex Military fast jet instructor so had the plane set up with traditional steam gauges & a Military style cockpit, it's impressive but very complex. I'm not a fan of glass even though my 'office' is same.
It's not as easy as it sounds to do a schem diagram, this RV8 is one complex electrical machine ! It's got the works? Everything is elect, even has a CD player & CCTV permanently wired in viewing underneath. the previous owner spent a fortune getting the machine wired to military specs, every connection & multi pin plug is of Military types, the wiring bundle/s under the panel would make a grown electrician cry! It's even got an AoA & a device to record & download all parameters onboard (yet to look into that!) The paperwork I got with the plane would sink the Titanic but no schematics….sob sob sob:-(
Ok what I have done so far.
I pulled the Cessna type switch (been flying for 40 years, never had an issue with same type of switch) my switch looks fine, no arcing evidence (which is odd considering that where the magic smoke came from), I will however replace the switch regardless of the outcome here. Power goes to the switch & leaves the switch as advertised. Every EI gauge has it's own CB, again none popped during the event in fact no CB's popped. This beast has more CB's than a B747!
I found the bus bar (terminal strip) that supplies power to all the EI gauges & my multi-meter shows 9.5 volts at every terminal, seems odd that low voltage but there is power there. I've looked high & low for additional in-line fuses, it's difficult for my frame (220lbs & 6ft 1") to get right under.
The previous owner an elderly gent who lost his medical & had the plane 17 years & rarely flew it (370 hrs TT when I bought is as a 19 yr old aircraft). The Maint Co that did all the original work many years ago have long since gone.
As previously mentioned everything else elct in the plane works just not the EI gauges other than the internal lighting which is off a sep dimmer switch, in fact the plane is set up for IFR flight with back up lighting, it's a masterpiece of work the whole plane!
My way of thinking is that obviously there is a loss of power to each gauge (a common power loss) or that each gauge has blown internally, unlikely (hopefully not!) I've not pulled the cowls off as yet to check firewall connections (multiple Military plugs) cause that's a PITA!

So here I am around Xmas time with my plane AOG, happy days.....NOT!

...............….more to come, watch this space:)
 
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If you you have 12v at the master switch (you did measure it, right?) and 9.5 v on the bus bar to the EI instruments you have a serious connection issue.

Disconnect the source to the EI bus and see if the source wire then goes to 12v.

If it doesn't check for poor connections - power and ground - along the way.
 
remove panel

Hi Adrian, Based on what I have read, here's what I'd do. I try to never work under the panel - it just causes frustration, pulled muscles, and a sore back.

  1. remove one of the screws to the panel
  2. get a handful of clecos that fit that hole
  3. Put the clecos and everything you need to unscrew the panel on the glarescreen
  4. Put your multimeter on the glarescreen
  5. Get a helper in case you missed something
  6. Sit in the pilot seat
  7. remove all the screws on the panel
  8. See if you can gently remove the panel and put it in your lap
  9. look for any sign of burns or bad wiring or something that does not look right
  10. If you need to get up, gently put the panel back and cleco it in place
I have a feeling you might be doing this several times in order to identify and fix the problem. I hope it works for you and you can find the source of trouble.
 
Okay everybody relax, problem solved!:)
The clue was the low voltage at the EI bus (9.5v) so looked solely at a short somewhere and found it by mistake actually! The ignition switch which is placed right next to the master switch was the culprit! The switch has been a little lose for a while didn't think much of it as it barely moved but what I believe might have happened recently was one day is was rather hot in the cockpit when parked out in the sun cause when I removed the ignition switch the insulation that was wrapped around the housing and multiple terminals had slid off the housing, the tape glue was all sticky as was the housing where it originally was placed, heat related I'd say. This allowed the switch which was slightly lose to drop a tiny amount on to the circuit breaker bus......bloody **** that was a PITA! Some new insulation tape, tighten the switch turn it all on and bingo......Santa was a day late...lolol

End of story guys, been an interesting experience!

Thanks again guys:)
 
I'm glad you found the problem. I'm guessing the tape that came loose was black vinyl electrical tape. I guess that would work OK, but you might consider some other options. Maybe that "self-fusing silicone tape" would work. You might also investigate all the different electrical tapes that 3M makes. Good luck!
 
the previous owner spent a fortune getting the machine wired to military specs, every connection & multi pin plug is of Military types

Electrical short due to tape slipping off the ign switch? Can't say I've ever seen electrical tape called out in a MSpec to prevent components from shorting together. :eek:

Using Mil-spec components alone does not equal a mil-spec quality installation, as you found out.
 
Okay everybody relax, problem solved!:)
The clue was the low voltage at the EI bus (9.5v) so looked solely at a short somewhere and found it by mistake actually! The ignition switch which is placed right next to the master switch was the culprit! The switch has been a little lose for a while didn't think much of it as it barely moved but what I believe might have happened recently was one day is was rather hot in the cockpit when parked out in the sun cause when I removed the ignition switch the insulation that was wrapped around the housing and multiple terminals had slid off the housing, the tape glue was all sticky as was the housing where it originally was placed, heat related I'd say. This allowed the switch which was slightly lose to drop a tiny amount on to the circuit breaker bus......bloody **** that was a PITA! Some new insulation tape, tighten the switch turn it all on and bingo......Santa was a day late...lolol

End of story guys, been an interesting experience!

Thanks again guys:)

Do I get the prize (post #14)? :D

The 9.5 v was the big hint. Volts should not get lost along a wire...
 
Electrical short due to tape slipping off the ign switch? Can't say I've ever seen electrical tape called out in a MSpec to prevent components from shorting together. :eek:

Using Mil-spec components alone does not equal a mil-spec quality installation, as you found out.

That's a bit of a smart a$$ comment, not helpful! Who's to say the tape wasn't added after the initial installation? The switch was loose that was the issue, the tape I assume was added latter most likely as a precaution!
To all the others (Gil) who where helpful thanks -;)
 
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That's a bit of a smart a$$ comment, not helpful! Who's to say the tape wasn't added after the initial installation? The switch was loose that was the issue, the tape I assume was added latter most likely as a precaution!
To all the others (Gil) who where helpful thanks -;)

Sorry no offense meant, my apologies.
 
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