I am wiring up a dash panel for my 32 build using a stewart warner stage 3 amp meter #338AD-R3. My question is; The Gauge has 3 posts on it. 2 that the mounting bracket fits over and 1 on the rear housing of the gauge. Is the post on the rear housing the ground connection? Are the other 2 posts that go thru the mounting bracket for; (1) the Hot Wire coming from the battery + and (2) the wire going to the Alternator power out terminal? No marking on my gauge to identify what goes where.
I don't think an amp gauge has a ground. I think the wire to the ign switch has the amp gauge inline. I couldn't find you gauge on SW site. What amp alternator are you going to have and how many amps will the gauge read.
I think that may be a mount for lighting. Is the stud on the top center of the back? And is it slotted on top near the face for gauge lights?
Looking at SW online they show three studs on the back of some of the gauges. Top stud shows ground for lighting. The mounting studs are also the wire terminals. The mounting bracket must be insulated from the bracket. As posted above a picture would be good.
Don't have a digital camera so no picture. I would use a voltmeter if I could find one that matches the rest of my gauges. The Stage 3 Stewart Warner gauges are from the late 70's, anyone out there have one for sale. The gauge needs a ground for the light. The holes on the mounting bracket are insulated with nylon so I think that the serious 10 ga wires mount to those 2 studs. The stud that I think is for a ground it just mounted to the back side of the housing. I don't want mess up the wiring up or the gauge will be toast when I warm it up.
The two studs should be insulated.(also mt'g.) run your alt/gen. wire to one, out the other one to the battery.....Oh yeah, if it reads discharge. switch them.. Z>>A volt. meter would just be + to one ,- to the other. the one stud could be grnd. for the light.
I like ammeters because they tell me whats going on at all times. When I step on the brakes, I get a flicker on the ammeter and I know my brake lights lit up. What does a volt meter tell you? You have voltage? whoopie When my ammeter quit working far from home it was very simple to move the wire to the other post and drive all night. No problem
Are you using an alternator? If so, ammeters and alternators are not good buds, alternators put out more current than a generator, there's always a possibility of the ammeter sticking closed, starting a fire. Not telling you to not use the guage, but be careful, as it has happened, if it were me, I'd figure on the load going through the ammeter, if you have a high zoot car with all the bells and whistles, be REALLY careful. If you have a more traditional car, no power windows or air conditioning, a pretty basic wiring system, I'd go with it, just keep an eye out for trouble.
Got that. I'll clarify. Other than that, is an AMP gauge a generator thing or do they have a purpose in an alternator system? Is there an advantage to having one?
A ammeter is actually a better choice if you're running a generator, and a voltmeter is better if using an alternator. This has to do with the electrical/mechanical differences between them and how they produce power. Both gauge types will give a general indication of charging system performance with either system, but in the most common 'failure mode' that each type has, a ammeter will be more likely to warn you of a problem with a generator, and a voltmeter will do the same for an alternator. A voltmeter does require that you be aware of 'normal' voltage output of your alternator system and a gauge accurate enough to reflect what's actually going on. As well as the safety issues of using a ammeter in an alternator system that can deliver 2-3 times the current of a generator. If the gauge isn't rated for the full output of the alternator, you are risking a fire...
From another forum, I can PM you the reference if you want it. As an electronics instructor before the digital age it is the best explanation I have found as to why I prefer an ammeter over a voltmeter in a vehicle. I have both in all of my vehicles. OldBuzzard ********************* cwheel, you are absolutely right, but then I'm an electronics engineer and I know you live or die by instrumentation. To me, the replacing-the-ammeter-with-a-voltmeter issue is a price point benefit for people that never look at gauges anyway. A voltmeter tells you if the alternator is making voltage, period. It CANNOT tell you if the battery is accepting a charge, nor can it tell you if it is a current drain problem or an alternator problem if the voltage is low. An ammeter tells you, relatively at least, everything a voltmeter does and more. A voltage differential is required to cause a current flow, so if the ammeter shows a charge, you KNOW the system voltage must be above the battery voltage. The ammeter tells you if the battery is fully charged yet, and if it charges for an excessively long time, you know the battery was excessively discharged or has a shorted cell. A voltmeter cannot tell you any of this. *************
Ammeter measures current through the system, Voltmeter measures the difference between two points (voltage). I heard someone once say that an ammeter measures 'flow' while a voltmeter measures 'pressure' or potential capacity - always found that helpful.
I hooked up an amp gauge years ago and it worked fine. After a few months I was in downtown Nashville and it decided to drain all the smoke out of the wires. I pulled the wires apart and it was very hot. So I ended up with 2 burnt hands, a burnt up gauge and burnt up wires. Never had an amp gauge after that. All the evidense was melted, but I'm sure 1 of the insulators quit insulating and caused the smoke and problems.
Chrysler products used ammeters for years, and they were the first to adopt the alternator (in 1960). The 2 mounting studs should be insulated, and used for "power in" and "power out" (thanks Chuckles) The remaining wire is most likely for the instrument light bulb power.
You'll find a lot of Voltmeters marked as ammeters in more modern cars. As has been said there have been many fires due to ammeters so make sure the gauge you use can handle the current drawn. The capacity of the alternator doesn't really matter - it could be 120 amps but it's how much current is actually going through the gauge. Some ammeters are of the shunt type where only a portion of the current drawn goes through the gauge - and some don't have any actual current going through them - like old Ford gauges the wire just passes through two loops on the back of the gauge and it reads the induction developed.
Pretty much all electric automotive analog gauges are just variations on the basic D'Arsonval movement, whether it's an ammeter, voltmeter, fuel level, tach, etc. All will have some sort of circuit to 'convert' the incoming signal to something the gauge can use, then the face is 'calibrated' to display whatever the value is you want. The only truly safe, easy to install ammeter is the inductive type mentioned above, but I've never seen an aftermarket unit like that. The remote shunt type is nearly as good, but wire size/length between the shunt and the gauge is critical for gauge accuracy.
AMP gauges are period correct in many traditionally built hot rods. All the early post war hot rods had AMP gauges/
I decided to make a remote pickup ammeter so I went to NAPA and got a 60 - 0 - 60 ammeter. I figured if I opened it up and took out the "big" resistor and put it in the alternator wire to the battery and ran small wires to the "small" resistor in the case, I would have a poor mans remote sensing meter. Nope. The D'Arsonval movement I expected to find is not there. Not much of anything is there. Just a very simple, cheap movement with a circular magnet between a pair of sheet metal ears attached to a copper strip. In trying to find out how this thing works, I ran across this: http://www.fordbarn.com/forum/showthread.php?t=95826&showall=1 #Post 20 Quote: Now here is one situation where cheapass 'ole Henry helps out. The ammeter in an A is NOT a sensitive D'Arsonval or 'taut-band' design with a moving coil of hair fine wire. The pointer is moved by induced reverse EMF into a non-magnetic pointer. It works just like a speedometer, but the pointer is centered so it can go both ways. Instead of a spinning magnet (speedo) the variable magnetic element is the brass shunt strip inside a wire ring magnet. You can put 30+ amps through it with the needle pinned and do no damage! That's exactly what happens when you have a short and see the ammeter needle pinned down past -20. Fix it, no damage. The worst that could happen with a huge instant 100A jolt would be to slam the needle hard enough to bend it, an easy fix. If you took it apart and glued in needle travel retarder you could slam it back and forth with amperage all day with no ill effect. Try that with a quality D'Arsonval or 'taut-band' meter and you'll be out $100+ in a flash! Thanks, Henry for being so cheap. You made it bulletproof. The 30A jobs sold by vendors are the same delightfully cheapass (and inaccurate!) design. Just use a stiffer needle spring or bend the field sensitivity tabs on the needle to recalibrate it for 30A at the travel limit. Side note#1- ALL aftermarket auto ammeters are of that cheap design that make them immune to extreme over amperage EXCEPT ONE. Post #20
To clarify things, you want the gauge on the battery side of the loads, not on the alternator side. It will tell you when the battery is charging or discharging, but doesn't read the output of the alternator. When everything is working as it should, the gauge will show 0 current. It should show a small charging current right after startup.
Wired this way you can tell if you have a stuck brake light switch. or you left the lights on. Can't tell that if you use a volt meter. I'm old school and always use an ammeter. It's a small thing but I always check the amp gauge before exiting the car. If the dome light or some other draw is on you will see it and not come back to a dead battery. Even on high out put alternators they work just fine. ( I hate alternators ;-) )
Several people are missing the point here.... Yes, if the ammeter is correctly wired and everything is working as it should, you'll have no problems. But this is not necessarily a fail-safe install. Yes, an inductive-type ammeter will be unlikely to suffer any ill effects in terms of it's 'movement' if it's range is exceeded. If you're using one where the connecting wire has no physical connection to the meter (like the Ford types mentioned) and the wire passes unbroken through/past the gauge, that is a fail-safe install. But if the meter does have two terminals requiring you to break the wire, then you're depending on the ampacity of the internal link in the gauge. For a gauge rated at 30-0-30, somehow I doubt that the designers used a link rated for a much higher current. Same thing will probably be true of a 60 amp gauge. So with the 'right' failure (failed alternator, broken output wire from the alternator to name two), you are now applying the full vehicle load across the gauge. If that load is within the ampacity of the gauge internal link, no problem. Sure, the gauge will read full discharge, but if you fail to notice it immediately and that link or it's connections fail because the load is beyond it's ampacity, as a best case you'll have zero electrical power, the worst case is the gauge shorts to ground and you now have a nice electrical fire... The whole point of a properly designed electrical system isn't to simply operate all connected devices, but to protect the system from damage in the event of failure. Installing undersized components is hardly helpful.
I just put a fusible link in the line to protect the system and the car. I had an alternator short out inside and the wire almost burned the truck up. A simple fusible link prevents this. A short blows the link immediately and all is well. Fix the short and the car is saved. An ammeter is not dangerous.
Again, the point is being missed. A fusible link may or may not give the protection needed. If you have a device whose 'failure point' is 50 amps for example and your fusible link is rated above that (even slightly), that device will still fail before the link clears the problem. Installing any device in a circuit that's not rated for the full circuit current available is just asking for trouble.
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