Battery/electrical problem
Battery/electrical problem Okay for a long while now my car has had intermittent problems dying completely. I just went out to the garage aND used my multimeter. What I find strange is if I measure positive to positive with the cable hooked up and to the negative without the cable it reads about 8.5 but if both the positive and negative are hooked to the battery I only get a ready of 2! Any ideas????
Joined: Nov 2003
Posts: 11,332
Likes: 347
From: Jacksonville, FL (originally from Toronto Canada)
8.5 and 2 what? Ohms of resistance? Amps of current? Volts? It would help to know what you're measuring and what problem you have that made you want to measure.
If you're talking about volts - check your cables. I had an issue with my original battery cables about 10 years after I bought the car new. The positive and negative cable that are pressed together in the same sheath that head toward the starter actually werre shorting out to each other. I pulled them apart and could find absolutely nothing that looked like a wire sticking through the cable but replaced them and everything was fine.
It might be an issue with another ground if you're actually talking volts as WhiteBird00 mentioned. If not, please specify and you'll probably get better answers.
It might be an issue with another ground if you're actually talking volts as WhiteBird00 mentioned. If not, please specify and you'll probably get better answers.
Yes I am talking about volts. My car has been dying very quickly and intermittently. Some days it would start right up and others it will be completely dead. Sometimes it will be ok for a month or so and others I have to jump it daily.
Joined: Jun 2011
Posts: 314
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From: Land of the Mormon's although I'm not one of them
Measuring positive to positive what? what are you measuring across?
You should have the positive of the meter on the positive of the battery, and the negative of the meter on the negative of the battery; you should see about 12.8V.
If you measure from the Positive of the battery to the frame/ground stud on the body/engine you should read about the same voltage. If you're getting a dramatically different reading, then your battery cables have issues.
You should have the positive of the meter on the positive of the battery, and the negative of the meter on the negative of the battery; you should see about 12.8V.
If you measure from the Positive of the battery to the frame/ground stud on the body/engine you should read about the same voltage. If you're getting a dramatically different reading, then your battery cables have issues.
Joined: Nov 2003
Posts: 11,332
Likes: 347
From: Jacksonville, FL (originally from Toronto Canada)
If you are getting readings of 8.5 and 2 volts then you are either using the meter incorrectly or you have a very serious electrical problem with your car.
For example, using the voltmeter with the positive probe at one end of a cable and the negative probe at the other end will tell you the change in electrical potential (voltage) between those two points. On a car battery cable (either positive or negative) this should be so close to zero as makes no difference. Getting a reading of 2 volts means you have catastrophic cable damage causing extreme resistance.
I can't think of any way to get a reading of 8.5 volts except with a dead battery.
For example, using the voltmeter with the positive probe at one end of a cable and the negative probe at the other end will tell you the change in electrical potential (voltage) between those two points. On a car battery cable (either positive or negative) this should be so close to zero as makes no difference. Getting a reading of 2 volts means you have catastrophic cable damage causing extreme resistance.
I can't think of any way to get a reading of 8.5 volts except with a dead battery.
it sounds like he measured 8 volts open circuit across the battery terminals- positive cable was hooked up to the battery but the negative cable was disconnected. Then with the battery connected he measured 2 volts across the terminals.
so unless he's using the meter incorrectly, he's most likely has a dead battery along with a draw on it when both battery cables are connected. It's normal to see a voltage drop across the battery when the doors are open and interior lights are on but engine not running. the battery should read 12.0 to 12.7 volts and it's not uncommon to read around 11.5 volts engine not running but you have doors open interior lights on and ignition key in run position. but 2 volts you have a dead battery. if the battery were good then for it to read 2 volts would be a massive discharge and you would have a fire or melted wires/metal somewhere.
so unless he's using the meter incorrectly, he's most likely has a dead battery along with a draw on it when both battery cables are connected. It's normal to see a voltage drop across the battery when the doors are open and interior lights are on but engine not running. the battery should read 12.0 to 12.7 volts and it's not uncommon to read around 11.5 volts engine not running but you have doors open interior lights on and ignition key in run position. but 2 volts you have a dead battery. if the battery were good then for it to read 2 volts would be a massive discharge and you would have a fire or melted wires/metal somewhere.
