Hi all, Recently I have finished putting indicators onto my 1969 750 which never had them installed before. I went to test the indicators and as soon as I put the live on the battery the fuse blew out. Thought it was the new indicators maybe earthing out so disconnected the power to the flasher relay to isolate and the fuse still blows and also went from 15 amps to 20 amp fuses which made no difference. However, for some reason if I connect the battery whilst leaving the headlights switched on the fuse does not blow. Not ideal as I have to remove the fuse or disconnect the battery. I'd also add I haven't tried to start the bike since this past month I've been working on fitting indicators (indicators don't work). But right now just want to problem solve why the fuse blows when the lights are off? Some old wiring but can't see any breaks and it's been reconnected as before. My electrical knowledge isn't good but I have a multimeter so any advicee on how to use it to work out whats wrong will be greatly appreciated. Many thanks
Lights on fine, but turned off the fuse blows
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Tornado
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I had some strange electric issues with fuses blowing etc...on a 74 850. Turned out to be the multi bullet connector block under tank...rubber wall between two isolated bullets had worn/split allowing random momentary contact. Replaced the multi block with double and single connnectors...much better insulated and better compactness.
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A 1969 model doesn't have that connector.
marshg246
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Since the fuse blows when changing the switch position - start there. May be a bad switch or a miss-wire affect by the switch.
I'm thinking of the black blocks which take 4 bullet connectors, 2 on each side which I have a few of inside the headlamp shell. If that's what Tornado is refering to? Edit: But yes, there is not a connector like that under the fuel tank
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Yes, worth a look. Think i have a spare switch of the same type to see if it solves it.
o0norton0o
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Unhook the battery terminals and connect the multimeter to the positive and negative leads of the harness. Put a good fuse in place. Turn the multimeter to the continuity setting where it makes an audible tone when you have a completed circuit. Troubleshoot your harness by disconnecting circuits until the multimeter tone stops. Once it stops, you've unhooked the circuit with the dead short on it.... then track that circuit to find the short circuiting issue. (or cross connected wire). If you remove the bulbs on a left or right side pair of blinkers that will interrupt the left or right side circuitry. Testing other circuits might require disconnecting a wire or a connector....
Electricity is logical... SO,.. if all of your circuits are supposed to be off and one is causing the tone on the multimeter, anything you do to cause that tone to go off is unhooking the circuit that has the short in it.
In the case of directional light circuits, pulling the bulbs on the same side together breaks the directional circuit for that side.... If it is your directional circuit I wouldn't be surprised if it's the actual "bimetal flasher unit" that is shorted..... I replaced mine with something called a "MOSTOP" switch.
Test,.... don't guess.. ©Concours 2022
Electricity is logical... SO,.. if all of your circuits are supposed to be off and one is causing the tone on the multimeter, anything you do to cause that tone to go off is unhooking the circuit that has the short in it.
In the case of directional light circuits, pulling the bulbs on the same side together breaks the directional circuit for that side.... If it is your directional circuit I wouldn't be surprised if it's the actual "bimetal flasher unit" that is shorted..... I replaced mine with something called a "MOSTOP" switch.
Test,.... don't guess.. ©Concours 2022
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No, as all four bullet connectors in each will be common, so it's unlikely to be the problem. However, replacing them (and any singles) is a good idea, as the old type can disintegrate because they're made from some strange monkey metal, the latest ones (below) are plated steel.
Good shout, just had a look at the multimeter and it must be the only one made with no continuity setting! So will have to get another tomorrow. Just to help anyone else out- The multimeter is made by LAP and Model no: MAS830B. Avoid it if you want a continuity setting.
marshg246
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No need for a separate continuity tester. Your multimeters has a resistance range. Set to 200. Simple continuity testers are a bad idea - often the connection is there but with some resistance and you want zero resistance across each connection.
Digital meters are a bad idea for old motorcycles - too much electrical noise. A $10 analog meter is much better than the most expensive digital meter for motorcycle troubling shooting.
I use this one, but it is overkill for motorcycle work (I also do electronics work): https://a.co/d/f179iTR
Okay and should increase space in the headlamp shell so its worthwhile swapping out.No, as all four bullet connectors in each will be common, so it's unlikely to be the problem. However, replacing them (and any singles) is a good idea, as the old type can disintegrate because they're made from some strange monkey metal, the latest ones (below) are plated steel.
Thanks marshg246, so set the resistance to 200 Ohms on the multimeter, connecting between the positive and negative leads of the harness and then disconnect different parts of the circuit to see if there is resistance and a reading of 0 means no resistance (good) anything other than this means there's a break in the wiring of the harness being tested. Is that correct?
And continuity testers being a bad idea - Does that apply for both digital and analog multimeters?
Deets55
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I have the same meter that Greg recommends and have been very happy with it. With that being said, I have used the same Craftsman digital multi-meter for the past 25 years and never had an issue with it on any vehicle I ever used it on, except my golf cart. That required an analog meter. There is a place for each type of meter.
I would avoid those cheap Harbor Freight type meters because they will mess you up when you least expect it. They might work OK for volts, but if you need an accurate resistance measurement they are extremely in accurate. I threw my in the trash because it almost left me stranded one time.
With much regret I had to retire my Craftsman meter because it suddenly became inaccurate. I tested it against my Fluke and found both DC and AC were off. I replaced that with a Fluke 15B I caught on sale.
I would avoid those cheap Harbor Freight type meters because they will mess you up when you least expect it. They might work OK for volts, but if you need an accurate resistance measurement they are extremely in accurate. I threw my in the trash because it almost left me stranded one time.
With much regret I had to retire my Craftsman meter because it suddenly became inaccurate. I tested it against my Fluke and found both DC and AC were off. I replaced that with a Fluke 15B I caught on sale.
marshg246
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A actual continuity tester will tell you if current passing and they will generally beep if there is low resistance. Having a few ohms of resistance is not acceptable in any connector or switch on your bike.
0 = good
infinity = not connected (break in the harness of there is supposed to be a connection)
Anything else = bad
Do this to learn your meter. With it set on 200 and leads connected to nothing it will do something to tell you not connected. Now still set on 200 touch the leads together. It must show zero. If not, then the leads are bad, or the meter is misadjusted, or the meter is bad.
To check a connection, with the battery disconnected, put one meter lead on each side of the connection - it must show zero.
Since you have a digital meter with a 200 ohm range, it is good for checking connections. As a voltmeter, it probably has trouble settling on a reading due to electric noise - an analog meter basically averages out the noise and therefore give you a consistent reading.
The display shows [1 . ] when not connected. When the leads are touching it shows [00.2]. Hmm... might be worth looking into an analog multimeter
That'll be another one to check. At the moment I'm going through the wiring harness looking for breaks in wires and replacing old connectors and then will reconnect and see if the fuse blows with the lights off.
Mart UK
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That's fine and to be expected. Your meter has some small resistance. So effectively, 0.2 Ohms is your zero point. I have never got a zero reading on mine and I always get some loss through electrical connector plugs etc. With your meter set at 0-200 Ohms, you are measuring Ohms, not Kilo Ohms, so unlikely to get a zero reading.
concours
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"Having a few ohms of resistance is not acceptable in any connector or switch on your bike."
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