Weird electrics problems getting weirder

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david pettengell
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Weird electrics problems getting weirder

#1 Post by david pettengell » Mon Aug 05, 2019 9:08 am

So, my previous post talked about my fuel and oil gauges not working properly, etc. Everyone's feedback was to check all earth's (grounds) so I did that. Cleaned and tested every single earth wire.

The problem has evolved to the point where the gauges are jumping around but now, when I switch on my direction indicators (either left or right) both the fuel and oil gauges jump in time to the indicators.

Also, when I switch on headlights, both gauges zero out (jump to zero and stay there). I have also noted that the indicator light on the dash does not flash when I switch on the indicators (but that could be a blown bulb).

Any ideas? I am completely lost!

Hoping my best mate CJ Murray will see this and pitch in ;-)

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Re: Weird electrics problems getting weirder

#2 Post by C J Murray » Mon Aug 05, 2019 10:00 am

I would suspect the ignition switch.
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Re: Weird electrics problems getting weirder

#3 Post by david pettengell » Mon Aug 05, 2019 10:08 am

Weird, we fitted a new one when we did the rebuild if you remember...

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Re: Weird electrics problems getting weirder

#4 Post by david pettengell » Mon Aug 05, 2019 10:11 am

Is there a way to test it Cliff?

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Re: Weird electrics problems getting weirder

#5 Post by C J Murray » Mon Aug 05, 2019 10:17 am

Get a voltmeter reading on all the troubled circuits and at the main power wire to the ignition switch.

BUT FIRST make certain that the battery ground cable is making contact and check the positive cable where both the large wire and smaller wire are clamped as well as the battery terminal.

If the starter cranks strongly then the cable post at the starter should be fine but check it anyway.

There is a ground cable at the front on the trans but that usually just bothers engine function.

The fuse blocks on our cars are riveted together and corrosion is common. One solution is to solder the rivet joints on the back of the block.

NOTE! Your engine popping is likely to have been caused by your poor electrical system condition!

Disconnect the battery while you are making changes.
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Re: Weird electrics problems getting weirder

#6 Post by Mike Wilson » Mon Aug 05, 2019 11:14 am

I suggested it previously but to reiterate, have you checked that the battery is properly hooked up?

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Re: Weird electrics problems getting weirder

#7 Post by david pettengell » Mon Aug 05, 2019 11:53 am

yep, checked the connection at the battery.

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Re: Weird electrics problems getting weirder

#8 Post by Mike Wilson » Mon Aug 05, 2019 12:40 pm

One item checked now onto the next. Since the ignition switch was replaced, as suggested, check the connections on that.
Doesn't the jumping gauges indicate a bad ground somewhere?
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Re: Weird electrics problems getting weirder

#9 Post by David Jones » Mon Aug 05, 2019 1:28 pm

Sounds like a ground/earth problem to me. Run a separate ground from the battery neg to the knurled nut that clamps the gauge in place and see if that cures it.
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Re: Weird electrics problems getting weirder

#10 Post by George Hussey » Mon Aug 05, 2019 2:36 pm

I AGREE it is a grounding problem. If the battery is fully charged and it does it with the key in the on position but not running, that it is a grounding issue, start with the neg battery terminal to the post and to the car and work back from there, look at the ground strap between the trans and the bottom of the body as well.
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Re: Weird electrics problems getting weirder

#11 Post by Don Gale » Mon Aug 05, 2019 8:49 pm

A voltage regulator on the fritz can cause similar problems.
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Re: Weird electrics problems getting weirder

#12 Post by david pettengell » Tue Aug 06, 2019 9:08 am

I was thinking voltage regulator but I know nothing!

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Re: Weird electrics problems getting weirder

#13 Post by George Hussey » Tue Aug 06, 2019 12:58 pm

usually a voltage regulator would make the lights dim and bright and the instruments not jump but rise as the engine revs, and turning on the headlights would not make the instruments die. Grounding problem
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Re: Weird electrics problems getting weirder

#14 Post by david pettengell » 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

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Re: Weird electrics problems getting weirder

#15 Post by neilbardsley » Wed Aug 07, 2019 7:16 am

David there is a very good 356b owner and electrician on DDK. Based near Worcester : Winston. Top bloke. Call him and he will be able to help. I believe that RPL maybe do a blade fuse box but I suspect that isn't your issue.

VEHICLE WIRING SERVICES (WINSTON TEAGUE/DAVID ASTON)
Address: Worcestershire
Phone: Winston Teague 07971 415277, David Aston 07968 225262
Email: vehiclewiring@googlemail.com
Website: www.vehiclewiringservices.co.uk
Services: Specialist historic and vintage vehicle electricians. Bespoke wiring harnesses designed, manufactured, fitted and commissioned.

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