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Ray White
Joined: 02 Dec 2014
Posts: 7140
Location: Derby
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 Posted: Fri Oct 17, 2025 5:51 pm Post subject: Reduced voltage. |
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The TC headlamps are not getting the full 12volts. In fact the voltage coming from the relays is only about half that!
I suspect a bad earth in area of the relays. Is it likely or possible? I have had problems with grounding in this area before. |
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MikeEdwards
Joined: 25 May 2011
Posts: 2713
Location: South Cheshire
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| Posted: Fri Oct 17, 2025 6:11 pm Post subject: |
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How good is the wiring? Is it newer than the car, or could it just have deteriorated?
_________________
1976 Vauxhall HP Firenza, 1976 Vauxhall Sportshatch (x2), 1986 Audi coupe quattro, 2000 Audi TT |
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Ray White
Joined: 02 Dec 2014
Posts: 7140
Location: Derby
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| Posted: Fri Oct 17, 2025 6:51 pm Post subject: |
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| MikeEdwards wrote: | | How good is the wiring? Is it newer than the car, or could it just have deteriorated? |
All the wires are new and all the connectors are soldered bullets. (I have probably just forgotten to tighten something.) |
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ukdave2002
Joined: 23 Nov 2007
Posts: 4242
Location: South Cheshire
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| Posted: Sat Oct 18, 2025 3:40 am Post subject: |
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| You haven?t by chance wired the headlamps in series? That would give you half voltage. |
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bjacko
Joined: 28 Oct 2013
Posts: 527
Location: Melbourne Australia
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| Posted: Sat Oct 18, 2025 9:54 am Post subject: Earthing |
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Good earths are extreme;y important on our old cars, rust between contact areas is one of the most frequent causes of poor earthing. I ran separate earths to many areas that previously relied on returning through body contacts to the chassis.
_________________
1938 Morris 8 Ser II Coupe Utility (Pickup)
1985 Rover SD1 VDP |
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Ray White
Joined: 02 Dec 2014
Posts: 7140
Location: Derby
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| Posted: Sat Oct 18, 2025 11:14 am Post subject: |
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| ukdave2002 wrote: | | You haven?t by chance wired the headlamps in series? That would give you half voltage. |
Now you mention it... I am trying to remember if I have wired the relays in series.
I suppose that would do it?
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Having dismantled hours of work to extract the bank of relays  I have reminded myself that the only series wiring that I did was with the earths.
I wanted to save space and thought a common earth would be O.K.??
All the other wires are installed in parallel .
Last edited by Ray White on Sat Oct 18, 2025 5:09 pm; edited 2 times in total |
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Ray White
Joined: 02 Dec 2014
Posts: 7140
Location: Derby
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| Posted: Sat Oct 18, 2025 11:17 am Post subject: Re: Earthing |
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| bjacko wrote: | | Good earths are extreme;y important on our old cars, rust between contact areas is one of the most frequent causes of poor earthing. I ran separate earths to many areas that previously relied on returning through body contacts to the chassis. |
No need to worry about rust. This is an Australian car and has no rust on it anywhere. I also run separate earths but mainly because it is a wooden body and there is a lot of new paint. Belt and braces really. |
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