Super Dave Posted August 4, 2013 Report Posted August 4, 2013 Our JPI 700 is not powered until the avionics master switch is closed; Is this typical? I'm thinking it would be nice to program/set up the monitor prior to engine start, but maybe the JPI needs to be isolated from power transients during engine start? How is your engine monitor installed? Quote
DonMuncy Posted August 4, 2013 Report Posted August 4, 2013 Mine is through the avionics switch. Quote
aaronk25 Posted August 4, 2013 Report Posted August 4, 2013 It should be on the avionics as Don's is. Unless your shop wired it to the master like Willmar did mine, even though the installation instructions specify the avionics. Quote
danb35 Posted August 4, 2013 Report Posted August 4, 2013 If the engine monitor is designed reasonably, there's no reason it needs to be on the avionics bus--that is, nothing going on on the master bus will harm it. The EI UBG-16 instructions specify that it be powered from the master bus, which is how mine is installed. I'd expect that would be a hard requirement for anything that's a primary instrument replacement. Quote
Bob_Belville Posted August 4, 2013 Report Posted August 4, 2013 My JPI EDM 930 comes on with the master switch. It has to be that way. Since it is primary, w/o the 930 there would be no fuel pressure before cranking and no oil pressure to check upon start. Or RPM or MAP... (The Aspen has its own switch, the rest of the panel is through an avionics "master" switch.) Quote
aaronk25 Posted August 4, 2013 Report Posted August 4, 2013 Mines a 830 non primary which is why it's on the avionics......and installation calls for avionics bus. Which I could covert it to a 930 Quote
Hector Posted August 5, 2013 Report Posted August 5, 2013 My 730 is on the avionics bus as well Quote
Jamie Posted August 5, 2013 Report Posted August 5, 2013 I found out my (admitedly ancient) GEM 600 is on the master switch. Once or twice I've had to turn the master off/on to reset the GEM because a gremlin got in there and made it (excuse me if I lose you as I transition to tech speak) go all wonky: Flickering, not responding to button pushes, not showing engine data. I guess it's either getting old or wasn't designed for it. OTOH, the master bus is probably a rough place for a piece of digital equipment to be. I'd be curious to see an oscilliscope trace of the master bus while starting. Quote
aaronk25 Posted August 5, 2013 Report Posted August 5, 2013 Only issue with master is I had to send the Jpi 830 back to jpi to get a hard reset be side the program got screwed up, which I think was from not starting right away after master on and the unit actually booted up and the low voltage from cranking caused the issue. I now immediately hit the starter after master on before it can boot up. I'm also going to get it re-wired to the avionics bus. Quote
Marauder Posted August 5, 2013 Report Posted August 5, 2013 I have a JPI 830 and EI rpm, mp and FP gauges as primary. The primary EI gauges are approved to be wired to the master, the JPI is not and is connected to the avionics master. I suspect the EI gauges have an electronic filter on them. Quote
orionflt Posted August 5, 2013 Report Posted August 5, 2013 My MVP-50 is a primary gauge so it has a circuit breaker off of the primary bus. Quote
Matt Ward Posted August 28, 2020 Report Posted August 28, 2020 Sorry to dig up a 7 year old topic...but I didn't want to make a new one for a similar question: My JPI 700 is wired to my master. I flip my master on, my JPI comes on. Here is what I didn't know that I just discovered: if the engine is running, and I flip my master off, the JPI (and the Hoskins fuel flow) stay on. Does that sound like a feature or a bug to you guys? On the one hand, I suppose it's getting power via the alternator that's still spinning, on the other hand, maybe I have a master switch/solenoid issue. Thanks! Quote
carusoam Posted August 29, 2020 Report Posted August 29, 2020 Matt, Modern engine monitors are sturdy enough to put up with the odd current waves they may endure during engine start... You can probably find out about your device by reading about it in the installation manual... The 700 series is not the typical primary type monitor... like the 900 series... So... you won’t know until you read it in the manual.... My 700 comes on with the avionics master... Is your 700 displaying anything related to engine start? MP, RPM, or OilP? If not, have your mechanic move the power wire to better location on the panel... PP thoughts only, not a mechanic... Best regards, -a- Quote
47U Posted August 29, 2020 Report Posted August 29, 2020 On 8/28/2020 at 1:34 PM, Matt Ward said: My JPI 700 is wired to my master. I flip my master on, my JPI comes on. Here is what I didn't know that I just discovered: if the engine is running, and I flip my master off, the JPI (and the Hoskins fuel flow) stay on. Is this anomaly affect only the JPI and Hoskins and no other avionics? Do you have an avionics master? What year is your E? There might be an explanation, but it sounds gremlish to me. Tom Quote
carusoam Posted August 29, 2020 Report Posted August 29, 2020 Hmmmm... There are things to know when it comes to wiring avionics masters... They are wired to prevent a failure of the circuit breaker to keep it from depowering your avionics... Looks like you proved the wiring theory of the avionics master to work perfectly! Avionics relay... is closed normally, it opens when the master Relay closes... it closes again with the avionics master being powered on by the avionics switch... The oddity you came across... When you turned the master off... it de powered the avionics relay... leaving it in the closed position... Congrats! I always wondered how to test that out... See what I mean? PP thoughts only, probably didn’t describe it completely... Best regards, -a- Quote
Matt Ward Posted August 30, 2020 Report Posted August 30, 2020 I do have a separate avionics master. The jpi and fuel flow do not seem to be part of its system. Quote
carusoam Posted August 30, 2020 Report Posted August 30, 2020 If it comes on with the master... Looks like somebody wanted to monitor the engine start with the JPI and FF instrument... My FT101 is on with the master... to monitor FF for start-up... including priming the engine... The O didn’t get a FP instrument... FF is the only monitor for fuel moving... Best regards, -a- Quote
Matt Ward Posted August 30, 2020 Report Posted August 30, 2020 Right, it comes on with the master, but doesn’t go off with the master! That’s the mystery. The engine provides it power too... Quote
carusoam Posted August 30, 2020 Report Posted August 30, 2020 To understand things better... Build a logic chart... Master on... Avionics on... What is the normal condition of each relay... open vs closed... What happens with each relay with each change... State #1: Start of the day, everything off... Master off... Master relay open... avionics switch off... Avionics relay closed... (important to know) no power goes to the JPI... State #2: Master on... Master relay closes avionics relay opens... no power still going to the JPI... State #3: Master on... Master relay closed Avionics on... Avionics relay re-closes (see this working?) Power goes to the JPI... State #4... (Abnormal shutdown or broken avionics relay wire) Master off, master relay de-energizes, and opens... no power going to the avionics relay, allows it to go back to the normally closed mode... Try flipping the avionics master... with no power going to it... it is stuck in its normal mode... it’s normal mode is closed... power is being supplied to it constantly this way... in its fail proof method... State #5... Normal shutdown procedure... avionics relay off... avionics relay opens... all the instrument and radios attached go dark... Engine off... By pulling the mixture... a few electronic devices are still on, attached to the master relay... Master off... opens the master relay... killing all power while the avionics master again closes... to its normal state. Somewhere in here is a latch I’m not describing fully... if both master and avionics are on... the avionics are powered... if master relay opens... it stops powering the avionics relay, that has already been de-energized by turning on the avionics switch... So... the only way to turn things off is in the right order..? It really helps to have the wiring diagram and the logic chart to figure this out... There is a thread around here describing how to win a bet and get a free beverage from your student pilot... You have just answered / solved the challenge, without knowing there was a question to be asked... Or a free beverage to be gained... Ask a CFI, because they must like free beverages... Ask a mechanic that specializes in the electrical side... they know how stuff is wired to be less failure prone... I’m only a PP, and not very familiar with this stuff... Best regards, -a- Quote
carusoam Posted August 30, 2020 Report Posted August 30, 2020 Matt, Find skip’s input here... Clear as mud... Best regards, -a- Where @PT20J said... “3. If you want to have some fun, bet someone your favorite beverage that you can turn the radios on by pulling a CB. Mooney realized that an avionics master was a single point failure and wired the relay as normally closed. The Radio Master powers the relay open when it is in the OFF position and removes power from the relay when in the ON position. So turn on the Master but leave the Radio Master off. Then pull the AUX CB and the radios will power up.” Quote
PT20J Posted August 30, 2020 Report Posted August 30, 2020 3 hours ago, 47U said: Is this anomaly affect only the JPI and Hoskins and no other avionics? Do you have an avionics master? What year is your E? There might be an explanation, but it sounds gremlish to me. Tom Something's not right. The master switch should turn off everything (except the clock and the infamous cabin lights that will drain your battery if left on). In your case, it sounds like your alternator field is active when the master is off so that the alternator is supplying power to whatever bus the JPI is connected to. I would get the schematic for your serial number and a good DVM and trace things out to figure out what's going on. Skip 1 Quote
carusoam Posted August 30, 2020 Report Posted August 30, 2020 Thanks go to Skip for adding the necessary clarity! Another always hot wire may be the cigarette lighter socket... If that is any help... Best regards, -a- Quote
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