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mroman59

Amp meter vs Volt meter

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mroman59
My wiring on my 7117 got fried at the switch. The switch went bad. I noticed the Amp meter was not working. A local parts dealer told me that when those amp meters go bad they send a surge through the wiring when turning the key, melting the wire. Instead of replacing the wiring harness, I bought a universal wiring kit which I spliced in and a new switch. I by passed the amp meter for now. He stated that John Deere makes an amp meter that would prevent this from happing again. 1. Has this happened to anyone else and is the parts dealer right? 2. My 6216 tractor has a volt meter instead of an amp meter and both tractors are about the same age. Why did Simplicity do this? 3. Would you put in a new amp meter or volt meter in its place? Thanks, MR

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D-17_Dave
First off, I don't believe in a surge. The electrical system will only carry the electricity from a source to a need. If there is a short it will cause an overload of the wiring and may result in damaging the wiring. Am amp meter measures the flow of electricity. The higher the flow the more the needle moves reflecting the flow and in what direction it moves. An amp meter only measures this flow, it will not reflect the condition or function of any component. A volt meter shows you the actual circuit voltage. Again just a dumb meter. However, how you use the information can tell you a lot. With the switch turned on, you can see the battery voltage and judge it's present condition. While starting the engine you can see the applied voltage drain to the system and judge the ability of the battery to perform. With the engine running you can see the charging voltage and judge to condition of the alt. and how well it works. You can do some of these tests with an amp meter but it takes a lot of experience and is spread over a lot more time. However it is not as broad in given information. Everyone used amp meters on engines with generators for decades. It took a lot of time for engineers to realize these facts and switch to volt meters which are much more user friendly over a broader range of equipment.

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timflury
quote:
Originally posted by SmilinSam
I assume you can just swap an existing ammeter and replace it with a voltmeter?
If you correctly wire the new voltmeter Sam, this can be done. Remember, an ammeter is wired in series. The meter is an actual part of the circuit. If you disconnect the ammeter, you must connect the wires together to correctly eliminate the gauge. A voltmeter is connected in parallel. the circuit will function regardless whether the meter is connected or not. You can disconnect the ammeter, connect the wires together on one post of the voltmeter, then connect the other wire to a good ground.

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larry8200
In order for the ammeter to cause a surge, it would have to be capable of storing a charge, there isn't anything in it that can... A voltmeter will show proper charging with increased voltage, around 14 volts, and a healthy battery will have about 12.5 volts resting. An ammeter only shows charge, which on a magneto engine without lights should be 0 most of the time except recharging the battery from starting.

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YellowB10
Id stick with an ammeter...that tells you the rate of current usage vs. current being produced by the generator. Gives you a much better indication of how well the battery is being charged...if a voltmeter were installed, youd get a measure of the overall voltage level of the entire circuit..which will mainly be the battery (~12v) unless diodes are installed in a way that you can measure JUST the voltage being produced by the generator (after its been regulated to 12v by the regulator). In this situation, its better to know current flow than voltage.

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BLT
Voltmeter tells you you everything. You don't need an ammeter, that just tells you flow (amps) at that point. A voltmeter meter tells you if that flow is enough to maintain a 13.5 - 14.0 volt battery charge while operating all your accessories and if the battery is at 12-12.5 volts prior to starting and when you hit the starter how far is the voltage being dragged down to or how resilient the battery is. You can also connect in to the ignition system if you have an accessory tab on the key switch.

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larry8200
quote:
Originally posted by Willy
Most amp meters flop around like a wounded tuna,unless the system is charging then it might be a little more stable. a volt meter will give you a steady needle.
Thanks Willy! I have been wondering how to describe some of my errant ammeters operation and "flop around like a wounded tuna" is perfect. I like a voltmeter. :D

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SmilinSam
Thats how the amp on my hybrid does. Even the digital meter set on voltage does this. But when I put the old analog meter on the system while engine is running it says steady at 13.5 volts. Havnt figured out what the problem is, other than the battery wont hold a charge.

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mroman59
Does everyone agree with timflurry's method above of of replacing the ammeter with a volt meter, i.e. connect the two wires from the ammeter to one post of the volt meter and then add another wire to ground? MR

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BLT
quote:
Originally posted by mroman59
Does everyone agree with timflurry's method above of of replacing the ammeter with a volt meter, i.e. connect the two wires from the ammeter to one post of the volt meter and then add another wire to ground? MR
Read the instructions. Some you can do the way Tim mentioned, some have separate terminal connections. My thoughts are to connect and tape off the existing wires and run a separate wire via the accessory terminal block which is powered by the ignition switch and a bond wire on the meter case it insure a good ground. All three of my meters are case grounded.

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timflury
quote:
Originally posted by Willy
Most amp meters flop around like a wounded tuna,unless the system is charging then it might be a little more stable. a volt meter will give you a steady needle.
I have a 2" DIGITAL voltmeter on my motorcycle. No needle to speak of.

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mroman59
Volt meter it is then. However, I think I might keep the amp meter wires together and tape them off instead of splicing them together to one terminal of the volt meter. You never know, when I am dead someone just might want my 7117 and want to restore it back to original and undo all my modifications. I would not want them to have to much trouble with the wiring, LOL. I will run a separate wire from the meter to the accessory terminal block instead. MR

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D-17_Dave
You can't hook up the wires to one terminal or off the accesory block before the switch. It must come off the switch after the power supply or it will cause a slow drain on the battery and stay on all the time.

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SmilinSam
I just swapped out my amp meter for a voltmeter last week. Just spliced the ammeter wires together and pulled the hot off the accesory side of the switch for the voltmeter and ran a ground to the frame. Also found the regulator to be bad ( starter generator system) and swapped another in. Its charging now. However, the voltmeter needle is still flopping around "like a wounded Tuna". Not near as bad as the ammeter needle did though. Cleanbee was talking to me yesterday about the regulators perhaps causing this. Can anyone elaborate more or point me to some literature on servicing regulators?

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mroman59
Sam, are you saying your switch had an accessory wire, not being used, on the switch that you used for the voltmeter? Therefore, you could actually put back the amp meter if you wish and have both, provided you have a dash board slot? My amp meter has those special connectors, i.e. the type that fit over the threaded connectors on back of the amp meter. I bypassed my amp meter when it went bad by taking a threaded bolt of the same size as the connectors, cutting off the head and then connecting the two ends on the threads and taping it off in case I wanted to use it again in the future. If I have an accessory wire on my switch, I would like to do it your way, rather than method suggested by timflury.

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