my voltmeter reads zero
08-31-2001, 04:33 AM
#1
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my voltmeter reads zero
Just recently, my voltmeter has dropped its reading to zero. I think something is wrong with my circuitry connections or something because the bass from my 4by6 speakers and pressure on the foot brake makes the light on my stereo face flicker and often the sound just cuts off for a few seconds.
I don't have a powerful sound system just two Eclipse 4by6 and rest stock, no amp. Does anyone know whats goin on, your input would be greatly appreciated.
I don't have a powerful sound system just two Eclipse 4by6 and rest stock, no amp. Does anyone know whats goin on, your input would be greatly appreciated.
08-31-2001, 10:55 AM
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Hard to troubleshoot one like this from long distance, but it sure sounds like you're getting a short when you apply the brakes.
Somebody may have installed sopmething without a fuse, or put an over-sized fuse in a circuit. I'd start by checking to see if the brake pedal arm or linkage (under the dash) is rubbing or pinching a wire, like maybe a speaker wire, or th epowr supply to the stereo. Then maybe check to be sure nobody has tapped into the hot side of the brake light circuit for a power source for the stereo or some other accessory. I'd also check the fuses in the fuse box to see if they match the factory size; if one is oversized, trace the circuit to see if there's either a bare spot on a wire or an added load on it.
Jim, "Jack Kevorkian for Senate physician!"
Somebody may have installed sopmething without a fuse, or put an over-sized fuse in a circuit. I'd start by checking to see if the brake pedal arm or linkage (under the dash) is rubbing or pinching a wire, like maybe a speaker wire, or th epowr supply to the stereo. Then maybe check to be sure nobody has tapped into the hot side of the brake light circuit for a power source for the stereo or some other accessory. I'd also check the fuses in the fuse box to see if they match the factory size; if one is oversized, trace the circuit to see if there's either a bare spot on a wire or an added load on it.
Jim, "Jack Kevorkian for Senate physician!"
08-31-2001, 11:03 AM
#3
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I would first track down that voltmeter problem starting with "is the meter broken."
Pressure on the foot brake? - I assume you must mean applying the brake - causing changes in stereo lights. Two things to go after. The brake linkage is pinching some wires. Or the electrical load of the brake lights is too much for some reason, maybe a short or someone rewired your stereo to the brake circuit. Pull the brake light bulbs and see if the same thing happens.
Pressure on the foot brake? - I assume you must mean applying the brake - causing changes in stereo lights. Two things to go after. The brake linkage is pinching some wires. Or the electrical load of the brake lights is too much for some reason, maybe a short or someone rewired your stereo to the brake circuit. Pull the brake light bulbs and see if the same thing happens.
08-31-2001, 04:38 PM
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I agree with IceShark on tracking down your known problem first.
In my experiences with cars in general is that the brake light circuit does draw a decent amount of current.
A couple of other things that could cause this problem.
1. Alternator is not produceing current like it should be.
2. Lose wire ground or hot in breaklight circuit or at alternator or battery.
I would start by checking the voltage at the battery with car off should get around 12V. Then start the car and see if the voltage steps up to 14V. Then apply the breaks to see how far the voltage drops. If you do not read voltag around the numbers I stated your alternator or battery are probably starting to die on you.
Post your results of the tests I mentioned and maybe we can help lead you in the right direction.
Tom
In my experiences with cars in general is that the brake light circuit does draw a decent amount of current.
A couple of other things that could cause this problem.
1. Alternator is not produceing current like it should be.
2. Lose wire ground or hot in breaklight circuit or at alternator or battery.
I would start by checking the voltage at the battery with car off should get around 12V. Then start the car and see if the voltage steps up to 14V. Then apply the breaks to see how far the voltage drops. If you do not read voltag around the numbers I stated your alternator or battery are probably starting to die on you.
Post your results of the tests I mentioned and maybe we can help lead you in the right direction.
Tom
09-02-2001, 02:20 AM
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well, my car's voltmeter reads dead zero with the engine on or off. Bass from the speakers or pumping the brake, i notice, makes the needle of the meter jump a little but not much.
I used my friend's battery charger today to check the life of my battery and it appears to be ok.
I used my friend's battery charger today to check the life of my battery and it appears to be ok.
09-02-2001, 02:00 PM
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Brian you need to check it with a hand held meter because there is a problem somewhere in your car with the one in your dash. If you would have 0V your car would not start.
Tom
Tom
09-02-2001, 02:49 PM
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.Hi I’m one of your 928 neighbors
Below is one of my previous post, I hope this helps,
Low battery voltage or bad grounds, overcharging and undercharging alternator can cause an erratic computer control. Any input sensor, example, TPS, CTS (coolant temperature sensor), relay can malfunction under these conditions. With the ignition off turn on the headlights for one minute after one minute turn the headlights off, connect DVOM set to DC volts, negative lead to negative post, positive to positive. A fully charged battery should read 12.6 volts. Anything lower than 12.3 volts, you need to charge the battery, with the main cables disconnected, of course. With the meter connected to the battery positive to positive, negative to negative, start the engine, turn on the headlights, heater fan, radio. This puts a load on the system. You should see 13.5 volts to 14.4 volts. Anything under 13.5 volts could be a bad alternator, bad ground or high resistance in the positive cable. Anything over 14.5 volts is an overcharging alternator. With the car still running, lights and accessories still on, place the negative lead of the meter to the negative lead of the battery post, place positive lead of the meter to a negative ground strap in the engine compartment. The ground wire should join the engine block to the body. No more than 0.10 volts should read on the meter. A good ground is 0.00 or 0.01 volts. If you have 0.20 or more you have a bad ground wire. You can use a jumper wire for the negative lead of the meter to the negative lead of the battery post, so you can reach the engine compartment. Just be careful and use common sense when working in the engine compartment when the engine is running. I hope you used soldered or crimped cable end connectors not those cheap bolt on connectors on your battery. You should check the alternator output directly at the alternator with the car running and all accessories on. If you still have a problem, have a professional diagnose the problem, then post their diagnosis.
Make sure you have the decimal in the right place on your meter.
Good luck,
Steve c
Below is one of my previous post, I hope this helps,
Low battery voltage or bad grounds, overcharging and undercharging alternator can cause an erratic computer control. Any input sensor, example, TPS, CTS (coolant temperature sensor), relay can malfunction under these conditions. With the ignition off turn on the headlights for one minute after one minute turn the headlights off, connect DVOM set to DC volts, negative lead to negative post, positive to positive. A fully charged battery should read 12.6 volts. Anything lower than 12.3 volts, you need to charge the battery, with the main cables disconnected, of course. With the meter connected to the battery positive to positive, negative to negative, start the engine, turn on the headlights, heater fan, radio. This puts a load on the system. You should see 13.5 volts to 14.4 volts. Anything under 13.5 volts could be a bad alternator, bad ground or high resistance in the positive cable. Anything over 14.5 volts is an overcharging alternator. With the car still running, lights and accessories still on, place the negative lead of the meter to the negative lead of the battery post, place positive lead of the meter to a negative ground strap in the engine compartment. The ground wire should join the engine block to the body. No more than 0.10 volts should read on the meter. A good ground is 0.00 or 0.01 volts. If you have 0.20 or more you have a bad ground wire. You can use a jumper wire for the negative lead of the meter to the negative lead of the battery post, so you can reach the engine compartment. Just be careful and use common sense when working in the engine compartment when the engine is running. I hope you used soldered or crimped cable end connectors not those cheap bolt on connectors on your battery. You should check the alternator output directly at the alternator with the car running and all accessories on. If you still have a problem, have a professional diagnose the problem, then post their diagnosis.
Make sure you have the decimal in the right place on your meter.
Good luck,
Steve c
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09-02-2001, 11:06 PM
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ok, i managed to get ahold of a digital voltmeter. I checked the battery several times with the engine turned off reads around 12.2v. With the engine on it reads 13.4v and when i tap on the brakes, it drops an average of .06v. With my heater, lights and radio on, the meter read 13.36v but read as low as 13.0v the other times i tested it. I still have not checked the ground wires because i am having trouble locating one and i still have yet to look under the dash, cause its such a cramped space down there, it's hard to stay there long. I will post my other findings soon.
09-03-2001, 12:39 AM
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Brian,
12.2v at the battery is only 50% charged,you need to recharge the battery 12.6 = 100%.If you can't get a reading of 12.6v when charging for 1hr, have it ck at a auto part store. It could be bad, ck the neg. cable at the battery also,then retest.
steve c 85 928S euro
12.2v at the battery is only 50% charged,you need to recharge the battery 12.6 = 100%.If you can't get a reading of 12.6v when charging for 1hr, have it ck at a auto part store. It could be bad, ck the neg. cable at the battery also,then retest.
steve c 85 928S euro
