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Help please... electrical/fuse blowing sort of problem diagnosis required


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Posted

I was, on reflection a bit of a div.

I was pumping up the front tyre with one of those plug in cigarette lighter lazy ass pump things, and decided to start the car while it was inflating the tyre to save time because I was late. Everything cut out and now there's no lights, gauges or anything when I turn the key. I'll get the multimeter out and start poking stuff with it, but mechanical/electrical stuff isn't my thing at all, so any idea 1. what I might have done, and 2. where to start looking?

 

I guessing/hoping it's just a fuse. Is that likely?

 

Any help appreciated. 

Posted

Erm, is it a modern car in which case it is probably fucked.

Have you checked the fuses?

Try a cold boot restart, i.e. disconnect the battery and reconnect if you know your radio code.

Posted

Was the battery  flat  as well as the tyre, to start with ...only you weren't aware it was almost flat ,and the pump took out the last bit of juice?    

 

 

Posted

1985 porsche 924, Tyre wasn't flat, just being topped up.

 

Battery was/is charged, and was powering the pump nicely, and giving the usual readout on volts gauge, power definitely went dead as I turned the ignition key.

 

I'm assuming a fuse, but curious if it could be anything else, because to be honest electrical stuff, like poker, breeds of dogs and types of hats is something I'm just never going to be able to understand. 

  • Like 1
Posted

loose connection on the battery ? Might feel tight , but tap them with a hammer..

 

 

 

If that doesn't work , the cambelts busted .... I'll take it off your hands for £200 :-P

Posted

Test the battery voltage first. It should read 12.66V, if it's fully charged. < 12.5 and it will need to be charged.

 

Find fuse box. Clip one lead to ground, and with the meter on the VDC scale, probe each side of the fuse box rails to see if you've got power to one or both sides of the fuse box. It should be equal as possible to the battery voltage. If no power is on either side, find the battery and see if its voltage is being distributed to the alternator (big red wire) and to the starter solenoid. If there is voltage to those devices but not to the output side of the fuse box, you need to start eliminating fuses...if no voltage is present anywhere, you may have melted a fusible link somewhere between the battery and the rest of the electrical system. It's also possible that the battery itself simply failed under load. Either have someone bring you a load-tester, or remove it and bring it to some local motorfactor to load-test it. Don't let them use a "toaster" on it; those are inaccurate at best. A carbon-pile load test is what is needed, though they've been replaced by digital devices now. If it has a big heatsink at the top and an analog meter, it's just a static test which loads the battery with heater coils, and is not much good.

 

It won't hurt to remove the clamps and file them a bit. If they're corroded a bit of baking soda & water will help clean 'em up.  Always disconnect the (-) side first, and reconnect it last! It could be something simple which would need to be eliminated first.

 

Did the car turn over at all? Did you hear a POP when you turned the key? Moar info plz...

  • Like 1
Posted

It sounds like a failure in the lead going from the battery to the starter or the smaller one linked to that on the starter going back feeding the rest of the electrics. It has 2 earths, one battery to bulkhead and another bulkhead to engine. Look at all these carefully, the starter is a bitch to get to, you need the car lifting. I don't think it has any heavy fuses, only the 2 rows above the passengers feet.

Posted

Turned out to be one of the battery connectors was loose, so a 10 second fix.

If it wasn't pissing down yesterday I'd probably have checked before posting this but I was preparing myself for something worse. Thanks for the help with this, I appreciate the replies.

Posted

Because to be honest electrical stuff, like poker, breeds of dogs and types of hats is something I'm just never going to be able to understand.

 

Lol!

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