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Author Topic: CB500 Ignition Switch Problem ?  (Read 573 times)

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Offline jaytee-nz

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CB500 Ignition Switch Problem ?
« on: June 22, 2018, 11:57:22 PM »
Putting the wiring back together on my 1972 CB500 but I keep blowing fuses.
Initially everything was fine but every now and again the fuse would blow as soon as I turned the ignition switch on, without anything being moved or changed.
Now it blows the fuse every time.
I tried fitting an old headlight bulb to the fuse box to save fuses but that blew as well !
I disconnected the two black / white wires to the coils in case one had gone bad that made no difference.
There are no loose wires touching the frame or other wires and the earths are all good.
The ignition switch is an aftermarket one so based on previous posts, I'm beginning to suspect the little man from China has escaped or has crossed some wires in there !
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Offline bryanj

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Re: CB500 Ignition Switch Problem ?
« Reply #1 on: June 23, 2018, 12:04:51 AM »
Easy enough to test with a multimeter set to OHMS but don't forget that when you turn switch on all the lives in the loom come on so could be a short anywhere, you could bridge the black and red in the loom at the switch block and see if a fuse blows then--if not switch duff, if so wiring fault
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Semi Geriatric ex-Honda mechanic and MOT tester (UK version of annual inspection). Garage full of "projects" mostly 500/4 from pre 73 (no road tax in UK).

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Offline jaytee-nz

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Re: CB500 Ignition Switch Problem ?
« Reply #2 on: June 23, 2018, 12:10:00 AM »
Thanks Bryan - I did check the switch with the multimeter and it appeared to be ok.
Can you give me some more specifics about testing it in case I wasn't doing it right.
Cheers - JT
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Offline calj737

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Re: CB500 Ignition Switch Problem ?
« Reply #3 on: June 23, 2018, 02:20:10 AM »
Remove the fuses. Use your meter and check for continuity on all HOT wires to ground (red probe on the suspect wire, black probe on an engine bolt, frame bolt, etc). If you get a tone, you have a problem.

You can check from the fuse block to ground on the BROWN, BR/WHT, and RED connections too. The only thing turning the key does is provide power to those circuits; if you have a short to ground it will be there without a fuse and power.
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"Of all tyrannies, a tyranny sincerely exercised for the good of it's victim may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated, but those who torment us for our own good will torment us without end for they do so with the approval of their own conscience." - C.S. Lewis

Offline jaytee-nz

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Re: CB500 Ignition Switch Problem ?
« Reply #4 on: June 23, 2018, 02:29:16 AM »
Great - thanks Cal.
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Offline jaytee-nz

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Re: CB500 Ignition Switch Problem ?
« Reply #5 on: June 24, 2018, 02:11:40 PM »
Took a while to track the issue down but the problem turned out to be a damaged bulb in the light panel. The contact at the end of the bulb had collapsed against the bulb body causing a short. As I read somewhere on this forum - electrical issues are hard to find but usually easy to fix !
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