Ignition Electrical Failure

Technical advice Q&A

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whooper
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#1 Ignition Electrical Failure

Post by whooper » Sun Jun 01, 2025 11:21 am

Hi, I have 1968 series 1.5 roadster in good running order but with an intermittent electrical issue. After running for a while the cars electrics will go completely dead. It is as if key has been turned off. Any electronics that rely on the ignition being on have no power. It can happen randomly while driving, and the car just dies, or when trying to start when warm. The headlights, that I don't think are affected by the ignition circuit, work fine. After a period of time that varies (but up to 2 hours) everything is fine again, ignition has power and I can start the car and drive......... Any ideas on what the issue could be and /or how to chase it down?

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tim wood
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#2 Re: Ignition Electrical Failure

Post by tim wood » Sun Jun 01, 2025 12:05 pm

Does the ignition key seem to get warm?
Overheating and failure of the ignition switch is not unknown

viewtopic.php?f=9&t=6885
Series 1 FHC purchased 50 years ago. Courted my wife in it.
Series 1 2+2 when the kids were small now sold.
Series 1.5 OTS in opalescent maroon, Californian car. My retirement present.

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DWW
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#3 Re: Ignition Electrical Failure

Post by DWW » Sun Jun 01, 2025 12:28 pm

I had that happen to me, the key use to actually almost get scalding hot but Luckily ignition was not affected. I ended up installing a 40A ignition relay which solved the problem. If your key gets hot during driving it is possible for the ignition switch to lose contact. This may be the only way to isolate the fault short of bridging the ignition switch by hard wiring it.
Danny

1962 S1 3.8 FHC (1012/1798)
2015 Range Rover Sport SVR
"Experience is something you don't get until just after you need it."

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mgcjag
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#4 Re: Ignition Electrical Failure

Post by mgcjag » Sun Jun 01, 2025 5:50 pm

Ignition key provides power to fuse 6&7 so you need to check the common points...the white wire from ignition switch to fuse 6 that's linked to fuse 7...so check the white connections....also the brown live into ignition switch.....I'm assuming you have a wireing diagram...when you car fails it's then time to get out a meter or test lamp and check the above....Steve
Steve
69 S2 2+2 (sold) ..Realm C type replica, 1960 xk150fhc

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DWW
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#5 Re: Ignition Electrical Failure

Post by DWW » Mon Jun 02, 2025 1:40 am

I also had a fuse go faulty, it was No6 and the fuse wire was making an intermittent connection, that didn't affect the ignition though.
Danny

1962 S1 3.8 FHC (1012/1798)
2015 Range Rover Sport SVR
"Experience is something you don't get until just after you need it."

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mgcjag
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#6 Re: Ignition Electrical Failure

Post by mgcjag » Mon Jun 02, 2025 6:56 am

Hi Danny....the ignition dosnt go through the fuses but the white from the key switch goes to fuse 6 this linked to fuse 7...so failure on this white or its connection to 6/7 will lose your ignition...ideally use the wireing diagram together with my post above...Steve
Steve
69 S2 2+2 (sold) ..Realm C type replica, 1960 xk150fhc

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JerryL770
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#7 Re: Ignition Electrical Failure

Post by JerryL770 » Mon Jun 02, 2025 10:44 am

Whooper - is your ignition switch combined with a steering lock, as per S2 cars?

If so new ignition switches are not available from the usual sources (I think). However, the ignition switch for the old Land Rovers is available and is the same except it does not have a lug on it to align with the correct location in the switch housing. But, it is easy to align correctly. When I replaced mine, it was a very tight fit and I needed to press it in with a G-cramp!
Jerome Lunt
1970 S2 FHC - Dark Blue, Red Interior, MX5 Seats
2008 MX-5 NC PRHT - now gone :sad:

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Topic author
whooper
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#8 Re: Ignition Electrical Failure

Post by whooper » Mon Jun 02, 2025 10:38 pm

Tim Wood, No I have not noticed that the ignition key gets warm

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Topic author
whooper
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#9 Re: Ignition Electrical Failure

Post by whooper » Mon Jun 02, 2025 10:40 pm

mgcjag wrote:
Sun Jun 01, 2025 5:50 pm
Ignition key provides power to fuse 6&7 ....Steve
Thanks Will look into that.

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