A voltage regulator question.

[TVATIVAK71]

Just replaced a B&C 201-1 with another of the same. The original issue was it seemed to be normal and the tolerances checked out fine with multimeter on the trouble shooting sheet. but at times (once every 6-7flights) while revving engine to turn around volts would spike over 15 and alt field cb/switch would trip. Figured I’d just try a new regulator.

Anyway I assumed changing it would be a plug and play. That’s how I’ve always treated them when changing out. Started it with only master on, then while running turned on alt field and avionics master. Immediately voltage indicator (CGR-30P) goes from 13.3 to 9.9 then super thick noxious smoke comes rolling from under panel. Shut it all down blew an extinguisher........yada yada yada.

When the smoke cleared the Alpha Systems AOA indicator (was in plane when acquired, ironically planned on removing it soon) CB was popped. The AOA indicator on dash has a coax cable to the magic brain box. This cable was very long and coiled up with two other AOA system cables. From the dash indicator coax connection to the brain box was completely torched and cable coverings were burnt and melted together.

After inspecting all the wires around the burnt stuff. Left AOA breaker out, started engine all indications good except voltage cycled from 9.3 to 13.8 several times then up to 14.2 at 1200rpm. Shutdown, started again this time no cycling volts just 13.9 at idle and 14.2 at fast idle. Did mess with pushing breaker in to see results (I know I know.....) no smoke, no heat. AOA indicator cycles though read outs then totally extinguishes. Forgot to check amps.

This just happened a few hours ago and now I’m starting the voyage of discovery and research on why this happened so I haven’t covered very many bases yet. Maybe that AOA system realized it wasn’t doing much good and decided to self destruct on the annual. It’s coming out now along with a thorough under panel inspection for any other damaged items.

So my question is after reading support literature for the regulator installation. Is it really just plug and play or did I omit some procedure to properly install?

Just gathering thoughts for now, I have to look forward to some under panel playtime. Cockpit fires scare me, had one once in a C-207........not fun. Today was a good lesson for a newly minted private pilot who was watching how quick, thick and toxic a cockpit can smoke up.

a crude pic of some burnt wires and pic of those coiled wires from AOA manual.

 

[wireweinie]

I'm thinking you have two separate problems. Unstable voltages are usually issues with connections. Look for any loose or improperly crimped terminals. Also look for bad connections at the contacts inside switches and breakers. Make sure the voltage sensing terminal on your reg is actually connected directly to the bus and not jumpered to a power terminal like we used to do. Another trick I've picked up is to run the ground wire from the reg to the case of the alternator. This bypasses any bad grounds between the engine and airframe.

As for the burnt wires, check to see if any of those wires have a common connection with any of your reg wiring. If so, check for improper connections such as a power and ground wire flip flopped. If that checks good, check for a pinched or chaffed wire grounding to the burnt coax.

Let us know what you find.

Web

 

[TVATIVAK71]

Will do!

Never thought of repositioning the VR ground to the alternator case. Found the VR ground wire connected to a frame screw posts? One of the ones that stick through firewall. Still lots of paint on it. Thanks for the advice!

 

[TVATIVAK71]

Started digging into it and realizing what kind of mess it is behind panel. Found some loose wires on breakers on top of panel.....it’s kinda nice thought to put them up there but it’s not friendly for any MX work. Those cables on bottom of panel make it a pain to reach up and work on stuff. Plus that AOA box and previously a MT reversible prop airspeed/pressure switch made access to any of those breakers and switches very difficult. After having built a VERY user and MX friendly panel on our other plane, I am throwing in the towel on this rats nest and going to do my own panel.

Just got an Atlee dodge panel blank and thanks to the many past threads on panel configuration I have a good idea on what I want and make MX easier. Maybe those wires catching on fire were a mixed blessing. Gonna keep those radios and install a iPad mini or garmin 760,796? Already have a cable for the Garmin 560 and a better way to access CB’s/switches. Better pic of burned wires and wiring in general.

 

[TVATIVAK71]

Could not pinpoint the reason the HUD coax cable caught on fire on the AOA System. Lucky it was zip tied with the two other coax cables so it only melted the coating on those. Did find two loose connections and several switches that the screws had backed out from the bus bar and they were resting on the switch tabs. Tidied up the grounding wires and organized the wiring and cables to allow much easier access to items. Left some space for any new CB’s or switches in future and nice not having to fish instruments thru cables. Thanks to the many folks threads on cockpit layouts all those discussions really helped. Plus everything works!

I really am satisfied now. Funny thing is the SIRS compass that didn’t work worth a damn on top of dash now seems to work somewhat ok mounted in the upper left corner of windshield.

 

[Steve Pierce]

Looks like a better layout from a mechanics and pilots standpoint.

 

[musket]

Trying to find a good place to mount a B&C LR3D-14 voltage regulator (VR), particularly from a maintenance standpoint -- and taking into consideration AC43.13-1B, (CH 1), Chapter 11, Section 8, para 11-96, sub para W -- having to maintain a minimum of 2 inches distance from the fuel line that crosses behind the panel, AND keeping electrical lines above fuel lines sure places the VR up high behind the panel and hard to get to. Any suggestions appreciated ...

BTW, this is an experimental SC if that makes any difference; and B&C recommends the VR be located in the cockpit area, i.e. aft of the firewall.

Thanks in advance, Folks,

Andy

 

[wireweinie]

I've never mounted one on the aft side for the firewall. I mount them on the upper, left corner area of the forward side of the firewall. Makes it accessible and keeps it close to an SD-20 alternator.

Web

 

[musket]

Thanks, Web -- I believe that makes a lot more sense than where I thought I'd have to locate it -- this 'lectricity stuff sure is fun, eh?

 

[wireweinie]

It's a living.

Web