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Thread: Voltmeter showing 9v across amp

  
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    Voltmeter showing 9v across amp

    Not sure whether this is to go in electrics or ICE, but my amp keeps cutting out everytime a heavy bass note comes along, it gives me an error code but it doesn't exist in the troubleshooting guide, the closest (very close) problems I can find says my battery is either under 8.5v or over 14v, or I need to check my alternator voltage.

    So went to B&Q, got a voltmeter, tested across the battery and across the amp. battery shows 13v but amp only shows 9v, tried it with ignition on and engine on, both readings are the same.

    Been charging battery up for 3 nights in a row now, so it must be fully charged, i'm guessing it could be my alternator? Checked all the wiring and its fully tight with a clear connection, no dust or rust between it.

    Any help?

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    Check the earth to the amp, a bad earth will cause high resistance and lower voltage to the amp. The fuse holder for the power could also have a high resistance causing the problem

    Only if the battery voltage and amp voltage were near enough the same would I say it's a alternator fault
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    Reet I will double check all the earths tomorrow mate, will get back to you!

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    Seeing as you have a voltmeter set it to ohms setting and go from the earth on the amp to the bolt for the earth by the back lights. You should have a very low reading of 1 maybe 2 ohms. You can do the same for the power but make sure it's disconected at the time
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    Only just got the voltmeter today and haven't had a play with it, how would i set it to ohms? took a picture....



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    Pictures not to clear but it looks like the ohms setting it to the top left, if you turn the dial anticlockwise one or two notches it will be on it

    is the ohms symbol (google search is great if it works)
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    Yeah I know about that much mate, it's got a x10 and a x1k setting, and also a variable resistance setting and I wasn't sure what to set it on.

    Just tried it on all possible settings and the reading gauge didn't move... Must be doing it wrong. I put one terminal on my amps earth point, and the other on the cars rear light earth point, with both the amp off and the amp on...Still nothing.

    Took a better pic of the voltmeter too so you get an idea:


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    I think maybe the meter won't read low enough resistances

    Go back to the DC volt section and go amp + and - to get a reading, then amp + and rear lights - and take that reading and finally go t the amp - and pop the boot interior light out (when it's on) and go to the red wire to get a final reading

    Which ever one shows 12v means the other wire on the amp is where the problem lies
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    Since I checked the earth yesterday after wiggling it about making sure it's tight, it's been working fine...

    Did the tests anyway, all three came up at 12v, maybe a slight bit over, but nothing in it tbh.

    Thinking it must have been a dodgy earth connection maybe, as it's been fine since I gave it a bit of a tug

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