My mind is getting too soft. I can't remember how to install an ammeter. Do I just splice into the ignition wire ? Or do I need to ground it ?
It usually goes inline between your battery and the heavy wire from the alternator or generator/voltage regulator. Current p***es through it at all times whenever the engine is running or a circut is in use and it reads the amps being drawn.
Decide if you really need one. Also, you need to size it properly. You don't want to use a 60 amp meter on an 80 amp alternator (peg the needle, make smoke, burn down garage). If you're doing it for nostalgia purposes, just stick it in, and don't wire it up. What you really want to know, is if the battery is charging. You can see that with a volt-meter. 10 volts and lower is bad, 12 to 14.5 is good. If you use a GM alternator that has the 3-wire (OK, so I'm not calling it a one-wire anymore, ha), you can make a nice idiot light that comes-on when the alternator stops making juice (belt, or alt bad).
To make the ammeter actully display current entering or leaving the battery, which is what they normally do, you need to connect it series in the wire that connects the battery to the rest of the car's electrical system (EXCEPT the big wire connecting the battery to the starter or starter relay) Be careful with the wire size, routing, clamping, and grommets, there's the potential to make the car melt down with sloppy ammeter wiring.
DO NOT install Amp gauge...they have a tendency to short out, cause a fire...destroy car, interior, garage, house, even if the car is not running... Install a Volt-meter... R-
Didn't this bit start with Wireworks? I see it repeated now and then, but in my experience I've never seen an ammeter fail. Perhaps true with a cheap-o offshore gauge, but never with a US made quality one. Has anyone seen or been directly involved in a car where the ammeter burned up . . . car fire or not? Auto voltmeters came into being because they were cheaper than an ammeter and wiring costs were less.
Don't know the answer to your first question, Jay, but the second is PERSONAL experience...happened in my rad '57...burned a lot of wiring up before I got stopped and got to the battery shut-off...happened on a trip to the lovely city of L.A...spent most of one day chasing and replacing wiring...Amp gauge shorted across causing m*** hysteria as I was traversing the bridge into Long Beach...way too much smoke and stench in the interior to see clearly... Will not own nor install an Amp gauge, US made or any thing else... R-
I rewired a 56 chevy big window that had a fire under the dash. The guy said he was just driving down the road when it sounded like a MIG welder went off, and smoke came pouring out. You could see where the ammeter arced over and set the harness to burning. Once the ammeter blew, the circuit was open, and the fire extinquished itself. Modern wires are hard to get burning. They do melt, which is expensive, but not as hazardous. I think if you clear out the area behind the ammeter and make sure nothing is flammable, it can be pretty safe. I think one of the problems, is that a lot of schematics in books and old cars didn't fuse this circuit. The ammeter was the fuse. I probably wouldn't worry much if you put a fusable link at the alternator, so that melted first. Plus today they have a lot of maxi-fuses that can handle what some of the larger alternators produce. If you have air conditioning, and a high power stereo system, then you might have a lot of current on this wire. You can weld with it Imagine (don't do it) taking two #10 wires and connect them to a battery, and then touching them together. Nice flame, gets hot. For me, it's easier to wire the alternator +bat wire to the starter through a fusable link wire to the solenoid, then it is to bring it into the interior, and then back out to the solenoid. Most of the radars I worked on (built in the late 50's) were designed to measure amps indirectly. They used what we call today, a clamp-on ammeter. You put a loop around the wire and measure the amps remotely. Large currents were kept out of the instrument panel, away from the hu-man. You just have to ask yourself if reading amps is necessary, when a voltmeter will tell you if the battery is getting charged.
If you want an ammeter and are concerned about fire hazard, use a shunt ammeter. Only 50-100 milliamps through the meter.
What about wiring a stock type ammeter in the dash of a car? Would putting a jumper wire across the terminals allow the gauge to still work but not fry if it failed?
Electricity 101: current takes the path of least resistance. A short across the terminals would disable the ammeter (ammeter has more resistance than a short). In which case, you might just wire from the alternator to the solenoid direct.
"If you want an ammeter and are concerned about fire hazard, use a shunt ammeter. Only 50-100 milliamps through the meter." That is exactly what caused the wiring fire in a '64 Malibu SS harness I had. The shunt broke! That left the entire load of the car's electrical system going thru the gauge which was designed for the milliamp current. Sure was exciting until I got the battery unhooked! The shunt looked like an old style ballast resistor. Chevrolet changed the design in 1965. I once had an old ammeter from a 50's mopar product which just had the wire p***ing thu a loop on the back of the gauge. You did not have to break the wire. It "sensed" the current like the clamp on ammeter in the picture above. No way the gauge could cause a problem. That said, I wouldn't use an ammeter on my worst enemy's car!
All you have to do is add a fusible link or a circuit breaker somewhere in that wire for those rare failures that probably are NOT the fault of the amp gauge. I did have a 70s GM alternator short out in traffic. Something inside the alternator broke shorting out the 10 ga. wire directly to ground. All the amps of the battery traveled up that wire through the amp meter in the dash out to the ground in the alt. The amp meter actually held up pretty good under that catastrophic load. It was toast but so was the alternator. Yes the cabin filled with smoke and it wasted the wiring. A voltmeter would not have changed a thing except for the smoke in the cabin. I was able to reach up behind the dash and yank the wire breaking the circuit and possibly saving the truck. With a volt ga. the wire would be buried in a bundle under the hood and probably would have burnt the truck down before the connection could be broken. So from then on I've added a fusible link in the 10 ga. wire. If something happens that causes this wire to go to ground, the link will pop and no harm is done. People love to blame the amp meter because it is in that wire but in reality they are not the cause. Most every car made before 1955 used an amp meter that carried twice the amperage of a 12V system without any pattern of car fires. (they did have safer generators though) I'm talking about on topic cars here where the headlights are probably the biggest draw on the system. A simple fuseable link and I bet you'll never have to replace your amp meter. They are the easiest ga. to find in a flea market because they don't go bad as often. 40stude was the wiring burnt on both sides of the ga. or just the battery side up to the amp meter? If the wire leaving the ga. toward the alt. was burnt then the ga. was a victim of the fire and not the cause. In my case both sides were distroyed eliminating the ga. as the culprit for the short. It was ruined by the alt. short farther up the line. If the ga. was at fault the wire melting would stop right there at the short. If the melting continued past the ga. then the ga. was not the short. IMHO
Just wire it up, I did, and don't be lazy about it. Pardon me guys but you know damn well you're going to be EXTRA cautious now right? Well so should everyone else after hearing your experience. Double, or triple insulate everything, use lock washers, make sure none of the wires are showing, they're all very good and tight and ya know maybe even install a quick disconnect under your dash. Which I know leads to more extremely hot wires running inside the car. It's really all whatever you want to do. Me, I just wired in my Ammeter and did it carefully, I insulated every damn thing and when I was done I used some strips of black duct tape to cover the back of the thing. I've had car fires, and they ****in ****. Just be careful. Don't blame it on the meter though, it's not the meter's fault, it's the electrician's.
Drtoner and Tommy bring up the most basic yet important points to consider here...that probably most problems blamed soley on the ammeter are likely the result of poor installation and/or poor insulation! Shorts don't normally just "happen"...they're caused. Either via vibration, loose connections, metal edges chaffing through wires, poor routing and poor planning. I like to go overkill when it comes to insulating and isolating wires, something learned from my days spent messing with 4x4s and off road vehicles. I came up with some habits that have served me well when wiring my cars: 1. Wire it like a fibergl*** car. That is to say, run dedicated ground wires to every component that might normally just be grounded to the body or ch***is. I like to run new ground wires (of the proper gauge) back to a common bulkhead on the firewall usually that is in direct contact with a heavy gauge battery cable going to the engine block and meeting the battery's ground cable. It's overkill, for sure, but it virtually eliminates any problems caused by bad grounds. 2. Wear a rubber! I use various pieces of rubber hose as well as rubber grommets to insulate all wires and harnesses that p*** through or lie next to anything metal. It isn't always pretty, although you can spiff it up with a little extra effort. It provides positive ***urance that no 'hot' wires will get chaffed and cause a short. 3. Fuse it! Cars use fuses (and fuseable links) for a REASON! To provide a fail-safe in the event of a component failure or short that leads to excessive amperage being forced through the harness! Fuses are cheap insurance against BIG problems such as fried components and fires! USE THEM! 4. Hold 'er down! You'd be surprised at how many shorts, fires and even explosions I've seen that were caused by a battery that was able to flop around hitting everything in sight or better yet...falling into the fan! Your old shoestrings or bungee cords are poor choices...use a REAL battery tray with a real, bolt-down system that positvely holds the battery in place! I've seen some nice, high dollar cars with batteries held down by nothing more than gravity! It's stupid...and ASKING for trouble! Bolt that ****er DOWN! (You won't get far in a lifted rig on a bumpy trail with a wandering battery...so I learned that lesson early!). 5. Clean and tight! Corrosion and loose connections account for many mysterious electrical problems. On my cars, I make sure every connection is tight, and I use this incredible stuff called No-Ox-Id that looks and feels kinda like ear wax, but once you put a light coat on every connection, it'll protect it against moisture and corrosion and insure a good connection for years to come. I'm sure there's other products out there that do much the same thing, but the stuff I use comes from YEARS ago when my Dad worked for Detroit Edison...it's as good as it gets! I've installed ammeters in my cars before and never had a problem with one. Of course, I didn't just pop it into the dash and d**** the wires over the headers and stick them through jagged holes in the firewall...so maybe that has something to do with it?! Like most any other component, it's only as good as the installation...you do ****ty work, or take a few shortcuts, and it'll come back to bite you in the *** later!
The problem is not with ammeters themselves, but with the fact that they require you to run more high current wires thru the firewall. Good post!
You are right. It's just my hot rod roots that I can't shake. The accessory 2 gauge panel was sold with the expressed intent of eliminating the "idiot lights". They were for idiots! Every young hot rodder in the late 50's was taught that. I want my gauges!
heh....I have one of those nifty old oil/ammeter SW gage panels in my 55, under the dash. The ammeter is not connected up, and the original GEN light lets me know how the alternator is doing.
Use the shunt type but add an inline fuse to the wire going to the gauge. use 14 awg to the gauge and 10 amp fuse it will be fine that way if you have to run an amp gauge. Gauges are a personal preference I use a voltmeter. If you use good wiring principles that have been mentioned in a few of the post here you should be fine.
louvers, Lose the amp gauge and go with a volt meter. All the replies say volt meter you can't go wrong. Putting in an amp meter requires a 10 gauge hot line to the gauge, do you really want that under your dash. I fried all my gauges in my "T" one time with a amp gauge hot line. Be Cool Cruiser 49
I just found my ammeter was shorted in my '37 packard gauge in my coupe. Burned up a couple sets of wires before I found it. I'm glad I found this post, which gave me the idea to check it. Yup. continuity between the gauge post and the dash! No bueno. Swapped it out for a spare I had.
I would offer my opinion but last time I hooked up amp gauge when I tightened connection under car the beast fired up and being in gear took off down the ramps. I chased it and stopped car before it left the driveway. That was 30 years ago. Gauge is still on the shelf.
Being the wiring guy at an auto dealership, I've seen a few burn jobs. It happened as people replaced generators with alternators and alternators with larger output models. If the vehicle has a 30 amp gauge and you add a 60 amp or higher alternator, bad things happen. The wires weren't designed to handle 60 amps and most of the time they don't as the current draw balances the input. When accessories are connected that draw more current than the system was designed for, the wires get hot and melt into the other wires in the harness.
Cars had amp meters for decades with minimal problems. The reason cars are burning up now, is that the generators that put out 20 or 30 amps at full charge, have been replaced with alternators that have an output of over 100 amps. The original gauge in the car only goes up to 30 amps, so the first time the battery gets low and the alternator starts to put out more then the gauge was designed for, you have a fire. Also a 50 year old, mouse eaten, oil soaked, sun baked, original wiring harness is a fire waiting to happen. So in any car that came with a generator originally, and now has an alternator, use a volt meter, NOT an amp meter. And if building a car, just use a volt meter.
Happened coming off the truck. Dumb*** internet purchase. ran to garage for cable cutters and then realized I didn't know where battery was. Not under hood. ripped out seat and cut cable. smoke came from steering column, under dash and under hood. required all new harness. wire to ammeter totally burned off.
Un-necessary risk in my opinion. Maybe a volt gauge but 11 years ago @squirrel answered the question. Nothing has changed in the universe since that would alter that decade old response.
Generators and alternators work differently, so the type of gauge you need to monitor them is different too. If you're running a generator, an ammeter will give the most useful information as to charging system performance. Alternator, you want a voltmeter. Vintage generators are also rarely found with more than a 40 amp output (the largest I've ever seen was a 50 amp unit), with most common units limited to only 30 amps, so finding a gauge with enough current-carrying capability shouldn't be hard. You still need to exercise care when installing one with wire routing and so forth, but the OEMs used them for years on generator-equipped vehicles with few issues.
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