Hey, can anyone out there tell me why the volt meter in my dash jumps around like crazy after while my car is warming up? I have a 50 Buick that i switched over to 12 volt. I ditched the ampmeter and put in a volt meter.Sometimes the voltmeter jumps around like crazy, sometimes it's stable and will then drop for a split second and go back to normal.Sometimes when it drops the engine will miss. any info on this will help. Thanks, GOBO
Did you just take out your amp meter and install your volt meter? If you did, remember the amp meter is installed in SERIES and a volt meter is installed in PARALLEL. If this is what you have done, you will probably will smoke your volt meter as the entire power for the vehicle is running through the volt meter. Unhook the volt meter, the car will probably stall..... If the car stalls, unhook the voilt meter and hook the two wires together (wires which were hooked up to the amp meter). Hook one side of your volt meter up to your power for your guages or another power supply, then the other side of the volt meter to ground. Hope this helps...
if you install a volt meter in series, it will measure the voltage difference across the places you connected it to, but it won't get fried....it has way too much internal resistance.
Squirrel: you are bang on !!! I just didn't want to get to technical for people who do not have an electrical background.... For some people, wiring confuses the hell out of people.
ummmmm.....are you sure you're not confused? you said in your previous post that all the power for the car would run through the volt meter....but it cannot, because the voltmeter has too much resistance, there would be no current flow. An ammeter acts like a wire, a volt meter acts like an open circuit.
Squirrel: just trying to help a fellow rodder out, with out getting into too much theory, hell why not also expalin hole flow to really mess people up.... Regarding all the power running through the volt meter, it depends where in the circuit the volt meter is installed, improperly...
I know you're just tyring to help, so am I.... It doesn't matter where in the circuit you put the voltmeter, it won't behave like you said it would. You can't "force" current through a high resistance electrical part like a voltmeter. Some guy named Ohm figured this out a long long time ago, and stated it as a law: Voltage = Current X Resistance You can play algebra with it and move it around to say:] Current = Voltage / Resistance If the resistance is high, current will be low. I know this is way too much theory for the HAMB, but the result of this is that if you take out an ammeter, and put a voltmeter in it's place (wired exactly like the ammeter was wired), the car won't start, and the voltmeter will not be damaged.
I guess I wasn't clear. I eliminated the ampmeter. I wired the voltmeter with the positive to the fuse panel and neg. to ground. Thanks Gobo Drifterscc.com
That's what's nice about the voltmeter: you get to see the problem visually. The suggestion about the voltage regulator (unless you have a one-wire alternator) is probably the best thing to check first. Open it up, clean the contacts (don't bend anything) and try it again. Replace the voltage regulator if it is ancient.
When you say sometimes the engine misses could indicate a loose connection, I would check all the batt connections and alternator as well. Also how much does the meter drop when it is acting up? If the problem is at idle maybe the alternator output is border line at that rpm with the pully ratio you have. Does it ever do this when warmed up or higher rpm? These are a few things to check. Good luck.
I don't have a volt regulator. I have a one wire alternator. If my fanbelt was slipping would it make the voltmeter bounce around like that? Thanks for the help, GOBO Drifterscc.com
Well that's important information. Where does the 1-wire go? Does it go to the starter solenoid, and then to the ignition switch? I'd disconnect the 1-wire from wherever it goes, and measure the voltage out of the alternator with no load. Could be the alternator is bad. If that checks out, I'd start pulling fuses until the problem went away. Put the fuse back in to verify problem comes back, and then replace, rewire, or clean-up whatever it is.
IT sounds like the hook up issue is solved. Which alternator are you using? An internally regulated one? If it's an external one, replace it, they're cheap at the parts house. You should keep an extra in the tool box anyhow, they have a tendency to **** out at inopportune times anyhow. I'm going to say that you may also have a floating ground somewhere. Start checking all of your ground points, clean the surfaces, dab a little di-electric grease in there and tighten the bolt back up after cleaning it nicely. Also-bond your battery to the block, to the frame, to the body. You can use braided strap, or just some cable with eyes crimped to the ends (like from a remote starter solenoid to starter) I prefer the braided straps. You can never have too much good grounding.
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