Huitt3106 Posted November 28, 2019 Report Posted November 28, 2019 I spent a couple hours yesterday trying to locate a small voltage issue that I previously posted about (over voltage). The only issue I found was the field wire being ever so slightly loose at the alternator connection on both the power and ground. In fact, the ground broke from the connector without much movement at all, so I repaired that. One other thing I did find was the analog voltage meter does not read the correct voltage. The battery reads right at 14 volts (when tested with a handheld voltmeter) but the mounted meter shows only 9 volts. My question is, where do people usually connect the mounted voltmeter to measure the voltage? Is there somewhere typical or is it just connected to power from the battery to directly measure battery voltage? I want to determine if the mounted meter needs replacing or needs improved connection. My battery has been moved to behind the cockpit. Sent from my iPhone using Tapatalk
Browncbr1 Posted November 28, 2019 Report Posted November 28, 2019 Use your multimeter to take voltage readings at each point starting from batter to main bus bar. Check continuity at each point starting at engine block to firewall to panel. THis will help you identify where any loose contacts are 2
tmo Posted November 28, 2019 Report Posted November 28, 2019 The voltage drop can very well be real, and be due to resistance somewhere along the path from the battery (where you measure 14V) to the volt meter (try measuring there with the same multimeter you used at the battery). Possibly check both grounds (battery and wherever the volt meter is grounded) and if that doesn't help, trace the path the electrons take from battery to meter. 2
Ragsf15e Posted November 28, 2019 Report Posted November 28, 2019 The guys above nailed it. You likely have voltage drop at an old and/or corroded connection. Start with the battery, then bus, then voltage reg, etc. Move through the system and find the drops. Also, this should be tested with master on, but engine off. I’m really curious how you got 14v at the battery? Should be like 12.5ish. Maybe a bit higher for the first few minutes after turning on the master, but it shouldn’t read 14v.
larryb Posted November 28, 2019 Report Posted November 28, 2019 One more possibility is the analog voltmeter is not reading correctly. I would verify that first. 2
carusoam Posted November 28, 2019 Report Posted November 28, 2019 +1 on meter accuracy... a nominal 12v battery gets charged at around 14v... Sitting with the engine off, the well charged battery will be closer to 12v... Something to consider... Best regards, -a-
Huitt3106 Posted November 28, 2019 Author Report Posted November 28, 2019 +1 on meter accuracy... a nominal 12v battery gets charged at around 14v... Sitting with the engine off, the well charged battery will be closer to 12v... Something to consider... Best regards, -a- This was more or less the reason for me asking the question. I was wondering where the mounted voltmeter typically is connected and gets its reading from? That way I can check that location directly with my multimeter to see if my gauge is reading incorrect (faulty) or if I need to dig deeper for a bad ground or connection. Sent from my iPhone using Tapatalk
Ragsf15e Posted November 28, 2019 Report Posted November 28, 2019 1 hour ago, Huitt3106 said: This was more or less the reason for me asking the question. I was wondering where the mounted voltmeter typically is connected and gets its reading from? That way I can check that location directly with my multimeter to see if my gauge is reading incorrect (faulty) or if I need to dig deeper for a bad ground or connection. Sent from my iPhone using Tapatalk My input is close to useless because I’ve got a jpi 930 not the original gauge like yours, but generally, voltage is reading at the bus. 1
Huitt3106 Posted November 28, 2019 Author Report Posted November 28, 2019 Okay, I’ll see if I can trace it to there. My gauge is not original but also not as nice as the jpi. Thanks!Sent from my iPhone using Tapatalk
Guest Posted November 29, 2019 Report Posted November 29, 2019 3 hours ago, Huitt3106 said: Okay, I’ll see if I can trace it to there. My gauge is not original but also not as nice as the jpi. Thanks! Sent from my iPhone using Tapatalk Dos this schematic help?
carusoam Posted November 29, 2019 Report Posted November 29, 2019 H, i don’t recall my C ever having a volt meter... amp meter, yes... volt meter, no... My 94 O, has an analog volt meter that is nearly useless for precision... and it only works while you hold the button down... For a quick digital reference, many MSers are using a portable Volt meter that plugs into the cigarette liter (65 spelling on the lighter). Volt meters are usually a simple device wired from the bus on one end, to a ground on the other... Further from the battery, the higher the risk of not being accurate... connected to the bus, they have at least one layer of CB protection... Old circuit breakers can be some pretty lousy conductors... The wiring diagram Clarence shared is spectacular... I don’t see either the amp meter or a voltage meter... the amp meter is usually a volt meter (calibrated to read amps) wired across the shunt, item #72 in the diagram... that would make a good place to measure volts as well... Measuring voltage permanently... there are advantages of measuring it in several places... the closer to the battery the better... Realistically, measuring the bus voltage is good enough, since that is where all your electronics are connected...if the charging system dies... you will want to know exactly how well the bus is performing... When the charging system is working, absolute accuracy of the voltage reading isn’t that important... when it stops working, it is really good to have lights from the zeftronics VR wired to the panel... either over or under voltage warning... Chasing the wires on your Volt meter will be a pretty easy task to see where it is attached... The wires may even be just a few inches long... You can get a really good look at the bus if the access panels can be removed... Chasing the wires from the back of the instrument might be easy, depending on what and where it is. The good part regarding Clarence's diagram... it show all the locations from battery to instrument panel where a dirty connection can be slowing down the electron flow... expect to find a few dirty connections that will benefit from being cleaned... starting at the battery and working through all the grounds... The coolest part of having a digital engine monitor... the volt meter is included... Use extra caution if collecting data with the engine running... most of what you want to know initially, can be measured from inside... with the engine off. PP thoughts only, not a mechanic... Best regards, -a-
Huitt3106 Posted November 29, 2019 Author Report Posted November 29, 2019 This is all very helpful. I’m planning to go back to the airport tomorrow and hopefully trace down an issue if there is one. Sent from my iPhone using Tapatalk
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