Weird electrics problems getting weirder

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david pettengell
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Re: Weird electrics problems getting weirder

#16 Post by david pettengell » Wed Aug 07, 2019 7:24 am

Awesome thanks Neil

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C J Murray
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Re: Weird electrics problems getting weirder

#17 Post by C J Murray » Wed Aug 07, 2019 7:30 am

david pettengell wrote:
Wed Aug 07, 2019 6:53 am
Ok, so I will spend the next weekend going through every single connection in the car. Does anyone have experience of the replacement fuse boxes that use blade fuses. Cliff, have you tried these?

Seems like consensus is a ground issue.

Cliff, wouldn't it be annoying if my engine popping was down to bloody ground issue
I haven't used the blade type box. It should be better but I have been fine with the originals. My race car has a universal blade type though. The original boxes often loosen their screws due to hot copper wire crushing a bit in use. Tips of fuses get corroded or the tabs they snap into get bent to a position where they do not exert enough pressure to hold the fuse securely.

Funky electrical connections often cause erratic engine behavior in old cars and bikes. I have mentioned this to you before. This is even more likely when modern ignition systems are used because they are more sensitive to voltage than good old reliable points. Even points are going to go wonky if the voltage is erratic enough.
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david pettengell
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Re: Weird electrics problems getting weirder

#18 Post by david pettengell » Wed Aug 07, 2019 9:11 am

Luckily I'm OCD so the thought of taking out every connection, cleaning and refitting, does not fill me with dread!

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neilbardsley
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Re: Weird electrics problems getting weirder

#19 Post by neilbardsley » Thu Aug 08, 2019 3:12 pm

david pettengell wrote:
Wed Aug 07, 2019 9:11 am
Luckily I'm OCD so the thought of taking out every connection, cleaning and refitting, does not fill me with dread!
LOL!

Personally I'm the exact opposite will seat there thinking about a searching routine to find the problem quickest by which time you will have checked all the connections.

Have a look at this site http://www.cyberwerkstatt.com/Members_O ... sembly.htm

You can use it to go from the battery to the gauges and check the voltage drop at each stage?

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Re: Weird electrics problems getting weirder

#20 Post by david pettengell » Fri Aug 09, 2019 3:28 am

Thanks mate very useful! Whereabouts are you in London?

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neilbardsley
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Re: Weird electrics problems getting weirder

#21 Post by neilbardsley » Fri Aug 09, 2019 8:31 am

Work in central London during the week but in Northamptonshire on the weekends.

david pettengell
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Re: Weird electrics problems getting weirder

#22 Post by david pettengell » Fri Aug 09, 2019 9:02 am

I work in central London all week and live near st albans, we should have a beer!

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Re: Weird electrics problems getting weirder

#23 Post by david pettengell » Sun Aug 11, 2019 2:34 pm

So, I spent Sunday checking every connection. I started with the battery connections and changed for some new clamps and it looked like I had been successful. The gauges stopped jumping almost entirely and they didn't drop when I switched on the lights. Success I thought. I put the car back together, spare wheel back in etc and started the car, the old problem came back!

Spent the next four hours cleaning and refitting all the connections, checking earths were all below 4 ohms. Still the same problem... FUCK!!!!

So, one weird thing I notices is that there is a really thick 1/2 inch cable and an earth cable running from the earth battery clamp. One of the cables goes straight to earth in the battery compartment but the other one disappears into the car alongside the thick positive cable. I looked at the official wiring diagram and it only shows one to earth, none to anywhere else. Is this normal?

So I am at the point of looking for professional help, thanks for the contact above. Any other suggestions?

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Re: Weird electrics problems getting weirder

#24 Post by C J Murray » Sun Aug 11, 2019 4:35 pm

david pettengell wrote:
Sun Aug 11, 2019 2:34 pm
I am at the point of looking for professional help
Don't bother. I've had professional help and it hasn't helped one bit! :shock:
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Re: Weird electrics problems getting weirder

#25 Post by Geoff Fleming » Sun Aug 11, 2019 4:49 pm

Before trying anything else, disconnect the strange cable. Now you should simply have the ground, ( 'earth'), cable and the positive ones at the battery. Start the car without the mystery cable being attached. Probably some previous 'genius' owner tried once again to improve on Porsche engineering.

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Re: Weird electrics problems getting weirder

#26 Post by C J Murray » Sun Aug 11, 2019 4:49 pm

david pettengell wrote:
Sun Aug 11, 2019 2:34 pm
I notices is that there is a really thick 1/2 inch cable and an earth cable running from the earth battery clamp. One of the cables goes straight to earth in the battery compartment but the other one disappears into the car alongside the thick positive cable. I looked at the official wiring diagram and it only shows one to earth, none to anywhere else. Is this normal?
Not normal. The question is why? Further, where does the other end of the extra cable terminate? The stock negative battery cable is this... https://www.stoddard.com/64461230100.html.html
Between the body and the transmission is this strap... https://www.stoddard.com/64461230500.html.html

A new fuse box isn't too expensive... https://www.stoddard.com/64461280100.html.html
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Re: Weird electrics problems getting weirder

#27 Post by david pettengell » Sun Aug 11, 2019 5:04 pm

Thanks both. I thought there was no reason for the extra earth cable. I think I will find out where the other end goes just for interest and disconnect. I hate electrics...

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Re: Weird electrics problems getting weirder

#28 Post by Robert Vaughan » Sun Aug 11, 2019 5:36 pm

The ground tie for the battery is often very poorly connected. The bolt for the L-bracket pulls the flat braid against a painted surface. I would not be surprised that your car may have a second ground connection at the battery for that reason.

The symptoms (weird behaviors) usually indicate a high resistance ground return connection. You want shiny metal, broad area, contact for the lowest resistance.

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Re: Weird electrics problems getting weirder

#29 Post by C J Murray » Sun Aug 11, 2019 5:56 pm

david pettengell wrote:
Sun Aug 11, 2019 5:04 pm
I hate electrics...
It could be worse, it's not a Joseph Lucas design. :P
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Re: Weird electrics problems getting weirder

#30 Post by david pettengell » Mon Aug 12, 2019 4:12 am

C J Murray wrote:
Sun Aug 11, 2019 5:56 pm
david pettengell wrote:
Sun Aug 11, 2019 5:04 pm
I hate electrics...
It could be worse, it's not a Joseph Lucas design. :P
Are you belitaling the British engineering again?

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