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Author Topic: voltage problem  (Read 297 times)
KD5LDW
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« on: April 08, 2005, 06:29:36 PM »

I own a 2004 FORD F150 ,My radio FT2800 is wired straight to battery with key off voltage drops to 11 volts then radio stops transmitting . I have hooked a Kenwood Tmv7a ,Icom 2100h does it on all 3 radios connections are good what am I doing wrong , thank in advance KD5LDW 73s
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W4JLE
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« Reply #1 on: April 08, 2005, 06:46:56 PM »

Sounds like a bad battery in the car. Drive down to the nearest autozone and have them check it for free.

What voltage do you measure at the battery terminals with the key off? If you have 11 volts at the battery terminals, there is definately a battery problem.
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KD5LDW
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« Reply #2 on: April 08, 2005, 07:11:39 PM »

12.1 with key off turn radio on it turns itself off crank engine works fine
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W4JLE
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« Reply #3 on: April 08, 2005, 07:23:21 PM »

What size wire are you running? If you have a 1.1 volt drop between the battery and the radio something is not kosher. With the engine running your getting 13.8 volts and that same 1.1 drop will still leave you 12.7.

I would suggest that you check the connections at the battery. How are they attached? Are you using lugs or simply twisting the wire under the connection screw?

Need input...
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AA4PB
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« Reply #4 on: April 08, 2005, 07:28:23 PM »

If you read 12.1V at the battery and only 11 at the radio then you have got to have a high resistance in the power or ground line to the radio somewhere. The radio probably draws less than 1A in receive. 1.1 ohm with 1A of current flow will drop 1.1V.

How is your radio grounded? Do you have a separate ground lead running back to the battery (you should) or are you depending on a chassis ground somewhere?

Check the wire, connections, fuse holders, radio plugs, etc.
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KD5LDW
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« Reply #5 on: April 08, 2005, 07:31:28 PM »

running lugs checked connections today good & tight running power cable supplied with Yaesu Ft 2800 truck is 2 years old sit on lot one year before I bought it I hope it is Batter & not some new type of deal FORD put on to save battery if I left something on by mistake
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KD5LDW
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« Reply #6 on: April 08, 2005, 08:02:02 PM »

radio grounded to battery with lugs all connections are good & secure
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OBSERVER11
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« Reply #7 on: April 08, 2005, 09:58:00 PM »

sounds to me as if you have a bad cell in the battery.

your truck should start with 2 bad cells, it would like it, but it can.

like someone said, drive on down to autozone or advanced or even the napa store and ask them to test under load.

do you hear alternator whine? I would thin kthat with a bad battery, you might. your am/fm radio would tell you quicker than the 2m radio.
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AA4PB
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« Reply #8 on: April 09, 2005, 05:35:17 AM »

Turn the headlights on (don't start the engine) and measure the voltage directly at the battery terminals. If the battery voltage drops much below 12V with this load then you have a bad cell.
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K1CJS
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« Reply #9 on: April 09, 2005, 09:53:00 AM »

One other thing you may try is the fuse holders in the radio power lines. If those clips holding the fuses are loose, there may be a voltage drop there.  Don't forget the inline power connector in the radio harness too.  Those may also be loose or making poor contact.  

If the negative is fused and the fuse is no good then the negative may be making a connection through the co-ax--resulting in a voltage drop depending on the quality co-ax and the connection from the shield to the car body at the antenna.

Take a meter and measure the voltage at each point the wire is interrupted (every connection point along the wires) for fuses, connection to the battery, power connector, etc. right up to the rig.  If the battery is good, chances are one of the connections are loose/bad.

Good luck and 73.  

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AG4RQ
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« Reply #10 on: April 10, 2005, 05:52:24 PM »

You may have a bad alternator. Never mind the age of the vehicle. I had an engine quit on a car that was slightly over a year old. Even if your battery is completely shot, you can still jump-start a car and drive it OK. I had a battery that was that bad. I would jump start it, drive it, and if I'd turn the ignition off, it wouldn't crank. A vehicle runs off the alternator once it is started. Do as was suggested. Have the battery checked under load. Consider checking the alternator next. You may have both a bum battery and a bum alternator. Just because the truck is running OK doesn't mean it won't quit all of a sudden. Its better to check it out than to be on the roadside calling for a towtruck.

73 de Mark
AG4RQ
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