battery connection screw up |
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battery connection screw up |
dt4 |
Jan 12 2020, 09:57 AM
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#1
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Senior Member Group: Members Posts: 502 Joined: 26-May 19 From: England Member No.: 23,161 Region Association: England |
I have had the battery off the car whilst stripping paint and priming etc.... but thought it would be good to turn the engine over and run it for a while to keep things in good health etc.....
I had the battery on the bench to charge it and then put it back in the car but very stupidly put the negative lead to positive terminal and positive lead to negative terminal. I didnt turn the key as I was checking other things when I realised what I had done. I noticed that there was a smell of smoke coming from the alternator area and the tin on top of the engine in that area was warm so suspect there is a connector to the alternator under there? I put the terminals on the right way around and tried to start the engine but it appeared the battery had drained? I recharged the battery overnight but wouldnt start, again the battery seemed low on charge Apart from seemingly screwing the battery, is there other damage likely to have occured cheers David |
Spoke |
Feb 10 2020, 12:47 PM
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#2
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Jerry Group: Members Posts: 6,972 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None |
About what could happen if the battery was reversed; check out the 914 charging circuit diagram below. With the battery connected correctly as shown, all the diodes in the alternator block current from the battery.
When the battery connection is reversed, the diodes are forward biased and shorted across the battery and will likely be damaged. Attached thumbnail(s) |
dt4 |
Feb 10 2020, 02:13 PM
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#3
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Senior Member Group: Members Posts: 502 Joined: 26-May 19 From: England Member No.: 23,161 Region Association: England |
About what could happen if the battery was reversed; check out the 914 charging circuit diagram below. With the battery connected correctly as shown, all the diodes in the alternator block current from the battery. When the battery connection is reversed, the diodes are forward biased and shorted across the battery and will likely be damaged. so it should just be the alternator that is kaput? I have had an hour checking the negative battery lead, the earth strap, live feed to the starter motor and any other wires to the body for good connections and earths. I didnt see anything untoward but cleaned them up in any case. No improvement, the starter barely responds. I did figure how to get a reading from the multi meter and it showed the battery to putting out 12.5v Is there a way of testing the power getting to the starter and the alternator? |
ctc911ctc |
Feb 10 2020, 02:40 PM
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#4
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Senior Member Group: Members Posts: 890 Joined: 9-June 18 From: boston Member No.: 22,206 Region Association: North East States |
About what could happen if the battery was reversed; check out the 914 charging circuit diagram below. With the battery connected correctly as shown, all the diodes in the alternator block current from the battery. When the battery connection is reversed, the diodes are forward biased and shorted across the battery and will likely be damaged. so it should just be the alternator that is kaput? I have had an hour checking the negative battery lead, the earth strap, live feed to the starter motor and any other wires to the body for good connections and earths. I didnt see anything untoward but cleaned them up in any case. No improvement, the starter barely responds. I did figure how to get a reading from the multimeter and it showed the battery to putting out 12.5v Is there a way of testing the power getting to the starter and the alternator? I would get another battery - i know you have tried another - however, this sounds like the battery is not juicy enough. Try this test, this may take two people: put the Volt meter on the battery and then when you grind the starter what is the voltage? If it falls close to zero - try another battery. If it stays above 8-9 volts - there is a wiring or starter problem. GOOD LUCK! |
porschetub |
Feb 10 2020, 09:47 PM
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#5
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Advanced Member Group: Members Posts: 4,696 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
About what could happen if the battery was reversed; check out the 914 charging circuit diagram below. With the battery connected correctly as shown, all the diodes in the alternator block current from the battery. When the battery connection is reversed, the diodes are forward biased and shorted across the battery and will likely be damaged. so it should just be the alternator that is kaput? I have had an hour checking the negative battery lead, the earth strap, live feed to the starter motor and any other wires to the body for good connections and earths. I didnt see anything untoward but cleaned them up in any case. No improvement, the starter barely responds. I did figure how to get a reading from the multimeter and it showed the battery to putting out 12.5v Is there a way of testing the power getting to the starter and the alternator? Try this test, this may take two people: put the Volt meter on the battery and then when you grind the starter what is the voltage? If it falls close to zero - try another battery. If it stays above 8-9 volts - there is a wiring or starter problem. GOOD LUCK! (IMG:style_emoticons/default/agree.gif) best way to test provided you have a strong battery,the starter pulls huge current,an old battery will tip over really fast with this load and a fully charged one will indicate a bad starter as appears you have checked all connections. 914 starters are pretty strong ,strip down and service it ,pretty easy. |
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