My last comment -- while out running yesterday the same thought occurred to me as Colyn -- is it possible the whole thing's in the EIS itself? Voltage cannot stay steady when amperage is running all over the place -- so what if the charging system is just fine, and you have a periodic issue in the EIS itself (or one of its connectins) that's causing bad indications? Again, the periodicity of it suggests to me that heat might be a factor, but that's just a guess.
As Mark Sletten suggested, just turning off the alternator briefly during one of these episodes should tell you a whole lot about whether it (and the regulator) are a factor.
On Oct 27, 2011, at 8:36 AM, Colyn Case wrote: David,
I had a problem with my GRT EIS that shares with your situation the possibility that something bad happening on one channel of the EIS is affecting some other channels on the EIS. In my case, one of my spade connectors in my EIS harness poked through to ground with the result that my tach went to zero. The solution in my case was to disassemble the entire EIS sensor wire bundle and put it back together with special care that nothing could ever poke through to anything else.
If it were my airplane I think I would first wire up a temporary ammeter/shunt and verify that your electrical system is okay. Then I would start disconnecting things on the EIS sensor bundle until I found the culprit.
Colyn On Oct 26, 2011, at 9:56 AM, Charley Brown wrote: Yeah, that's what I'm thinking. Steady voltage and wildly fluctuating amps in a simple system like that just cannot both be true. Possibilities: 1. Ammeter is not correctly calibrated, and the actual swings are a lot smaller? But actually, the 15 amp value seems reasonable in a 12V system; my 28V system pulls about 8-9A when the big loads are off (pitot heat, landing lights). 2. The fact this effect cycles regularly, and doesnt occur for a while in the first place, suggests a heat-related problem -- regulator heating up, shutting off, cooling down, starts to work again, heats up, shuts off, cools down...?
But like the other guys said -- check the wires first.
Thoughts worth what you paid for them.
CB On Oct 26, 2011, at 5:21 AM, Dennis Johnson wrote: If the voltage is steady at 13.8 while the amperage is fluctuating from plus 15 amps to minus 50 amps, then either the voltmeter is broken or the amperage reading is incorrect. My guess is the amperage reading is wrong. Is there some kind of electromagnetic interference that is causing the amp reading and the fuel gauges to go haywire at the same time? Is the hydraulic pump cycling every five minutes and doing this? I don't think hydraulic pumps are common antagonists, but I can't think of anything else that might cycle every five minutes. It's always a good idea to check grounds, but my guess is EMI. Interesting problem! Dennis ----- Original Message ----- Sent: Tuesday, October 25, 2011 6:00 PM Subject: [LML] Re: Problem with Fluctuating Amperage
Voltage reads steady at 13.8 volts. Amp drop is on the EIS unit, so the EFIS unit is not the cause. Good idea on downloading data. Dave T. From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Dennis Johnson
Sent: 10-25-11-Tue 14:01
To: lml@lancaironline.net
Subject: [LML] Re: Problem with Fluctuating Amperage What is the voltage reading during this time? Does the Grand Rapids EFIS Sport record data that you can download and study after a flight? ----- Original Message ----- Sent: Tuesday, October 25, 2011 4:50 AM Subject: [LML] Problem with Fluctuating Amperage Any ideas about what would cause my amperage to start fluctuating wildly about 5 minutes into a flight?
It starts out fine after takeoff at 15 amps and then goes to -50 amps for 30 seconds, and then gyrates between 5 amps and -50 amps for a minute and then goes back to normal. It repeats this sequence every 5 minutes.
My fuel gages also go down to zero during this episode and then back to normal.
Is my B&C LR3C Linear Regulator going bad?
(I'm getting these readings from my Grand Rapids EIS engine monitor. It's hooked up to a Grand Rapids EFIS Sport.)
Thanks for the help!
David T.
Legacy RG
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