Voltage drop issues
- ZoomsJr
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Voltage drop issues
19 Mar 2019 15:01
To start, I’ve cleaned just about every connection I can see under the tank and behind the headlight, checked engine ground, replaced the ignition switch, cleaned the kill switch etc etc. The problem is that without the ignition on, the white wire to the switch gets battery voltage. However, as soon as the ignition is switched on the voltage to the same white wire drops to 2.5-3V. Anyone have any ideas?
1978 KZ650 B2A
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- SWest
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- 10 22 2014
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Re: Voltage drop issues
19 Mar 2019 16:02
Could be the load after the switch or a wire that has been overloaded and is acting as a resister due to being overheated.
Steve
Steve
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
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- Warren3200gt
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Re: Voltage drop issues
19 Mar 2019 16:21
Or even the ignition switch itself. A few weeks back I had a solder joint on an aftermarket ignition switch fail and break. A bad soldered connection would cause resistance. It was an easy fix on mine, but not by the roadside

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- ZoomsJr
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Re: Voltage drop issues
19 Mar 2019 17:45SWest wrote: Could be the load after the switch or a wire that has been overloaded and is acting as a resister due to being overheated.
Steve
Thanks for the idea Steve, what the best way to figure out which wire may be acting as a resistor is this is the case?
Also I forgot to mention the the ignition switch is brand new
1978 KZ650 B2A
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- SWest
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Re: Voltage drop issues
19 Mar 2019 18:44
With my 40 year old loom I ran a new white and brown wire. In the wreck the white wire was toast so I combined a KZ 900 loom and ran it in 87. Because of old/bad connections I had to change switches and loom again.
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
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- Warren3200gt
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Re: Voltage drop issues
20 Mar 2019 04:46ZoomsJr wrote: Also I forgot to mention the the ignition switch is brand new
As was mine, someone should teach the Chinese to solder!
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- loudhvx
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Re: Voltage drop issues
20 Mar 2019 06:07
Besides the switch,. a very common place to lose voltage is at the fuse holders. They get dirty and start to have resistance. See if the wires in the fuse box look burned or melted.
1981 KZ550 D1 gpz.
Kz550 valve train warning.
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Kz550 valve train warning.
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- ZoomsJr
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Re: Voltage drop issues
20 Mar 2019 07:51
Fuse box is brand new as well, old one melted around the main fuse. I believe the previous owner had a 25A fuse instead of a 20 for the main,
1978 KZ650 B2A
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- SWest
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Re: Voltage drop issues
20 Mar 2019 07:59
Check your grounds too.
Steve
Steve
Z1b1000 1975 Z1b
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
kzrider.com/forum/11-projects/598262-kz-...-will-it-live#672882
kzrider.com/forum/2-engine/597654-poser?start=240#704229
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- ZoomsJr
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Re: Voltage drop issues
20 Mar 2019 08:20SWest wrote: Check your grounds too.
Steve
Cleaned (sprayed and buffed) the engine ground but I still have .5-1 ohm resistance on the case with a super cheap multimeter
1978 KZ650 B2A
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- Warren3200gt
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Re: Voltage drop issues
20 Mar 2019 08:20 - 20 Mar 2019 08:21Fuse box as in the plastic case? Its the fuse connectors that need checking and cleaning unless it came with anew loom bit as well?ZoomsJr wrote: Fuse box is brand new as well, old one melted around the main fuse. I believe the previous owner had a 25A fuse instead of a 20 for the main,
Last edit: 20 Mar 2019 08:21 by Warren3200gt.
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- ZoomsJr
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Re: Voltage drop issues
20 Mar 2019 09:08Warren3200gt wrote:Fuse box as in the plastic case? Its the fuse connectors that need checking and cleaning unless it came with anew loom bit as well?ZoomsJr wrote: Fuse box is brand new as well, old one melted around the main fuse. I believe the previous owner had a 25A fuse instead of a 20 for the main,
The new fuse box is the one from z1 which includes the plastic case, fuses, as well as the pigtail and red/white striped wire and white wire with bullet connectors
1978 KZ650 B2A
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