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Joined: Feb 2006
Posts: 6
Newbie
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OP
Newbie
Joined: Feb 2006
Posts: 6 |
Not a contour problem, but I thought you guys might could help me with a general electrical problem. I'm helping a friend try to get his radio and clock working again. It seems the power supplied to the clock and radio when the car is turned off is really low (measured 1.6 volts). I assume it should be ~12 volts? Any ideas what would cause it to be so low? I thought it might be a short, but wouldn't a short cause the fuse to blow and the voltage to go to zero? Any suggestions on tracking down the problem?
Thanks!
Josh
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Joined: Sep 2000
Posts: 4,693
Hard-core CEG'er
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Hard-core CEG'er
Joined: Sep 2000
Posts: 4,693 |
More likely a bad connection causing high resistance. Start by checking all the connectors you can find in the circuit. As you move from the point you measured the low voltage, read the voltage again at each connector as you go.
Jim Johnson
98 SVT
03 Escape Limited
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Joined: Feb 2006
Posts: 6
Newbie
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OP
Newbie
Joined: Feb 2006
Posts: 6 |
Ahhh, that makes sense. I'll report back and let you know how it goes. Thanks for the help.
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Joined: Mar 2004
Posts: 536
Veteran CEG\'er
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Veteran CEG\'er
Joined: Mar 2004
Posts: 536 |
btw
you should have no more than about a .2V drop at any one connector or .5V for the whole circuit
97 contour gl mtx
front & rear upper strut tower braces
19mm bat sway bar
Koni struts w/GC knockoffs
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Joined: Sep 2002
Posts: 1,788
Hard-core CEG\'er
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Hard-core CEG\'er
Joined: Sep 2002
Posts: 1,788 |
Originally posted by striker2:
btw
you should have no more than about a .2V drop at any one connector or .5V for the whole circuit
You're way too generous with those drops in a low-current circuit.
Steve
98 Contour SE Sport 2.5 Duratec ATX The wifey's car
89 Taurus SHO - 246K miles
94 SHO ATX - 190K
1997 F-150 5.4L ATX - The Workhorse 150K.
ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!
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Joined: Sep 2000
Posts: 4,693
Hard-core CEG'er
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Hard-core CEG'er
Joined: Sep 2000
Posts: 4,693 |
Originally posted by projectSHO89:
Originally posted by striker2:
btw
you should have no more than about a .2V drop at any one connector or .5V for the whole circuit
You're way too generous with those drops in a low-current circuit.
Steve
Those are reasonable numbers for the starter with it's high draw, but it would be too much for a low draw current like a stereo system (unless you have a killer stereo).
There is an easier way to measure voltage drop that is far more accurate than just reading the total voltage. Set the voltmeter to 2 volts. That's right 2 volts. Not 20 volts, not 200 volts, not .2 volts. 2 volts. Don't try to take readings with one probe on the hot wire and the other one on ground. Instead, two different points on the same hot circuit. For example on a starter circuit, one probe on the battery positive terminal and the other on the starter hot post and take the reading under load (starter cranking). That will give you a very accurate starter voltage drop. You can (and should) do the same thing on the return circuit (ground). Place one probe on the battery negative terminal and the other on the starter housing and take the reading while cranking. You would be surprised how often the problem is in the ground side.
For a low current circuit you don't want anything above .2 volts voltage drop, and actually even that is liberal. You should try to get it as close to 0 as possible and you usually can.
Jim Johnson
98 SVT
03 Escape Limited
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