Harley starter relay upgrade

[Lyle Manheimer]

Ok, now I understand. bike will start with the heavy duty momentary switch under the seat, that is wired from the battery post on the solenoid to the small terminal on the solenoid. Bike will also start with the old tried and true screwdriver trick across the solenoid main terminals.
Trouble shooting is a process of elimination. Keep in mind each point you check you should see close to battery terminal voltage, with the wire lifted at the solenoid. You checked for a voltage drop with the wire connected and the starter cranking. A drop to 7 volts there makes me question the health of the battery.
Your under seat switch has bypassed all of the wiring and terminal points in the start circuit, so with the control wire lifted at the solenoid you should start your point to point voltage drop tests in the original start circuit. Start with the can relay out put pin to the solenoid and work your way back to the start push button. The terminal plug must be checked as well for a voltage drop. A resistance check across the plug can be miss leading. Voltage changes everything.

[dukekleman]

Things to remember, always voltage drop with a 100% charged battery. Your sum should equal 0.6 VDC or less. Remember to make the circuit active (Biggest thing I see Techs forget to do when I'm training) . Indeed 7 vdc is very bad. Move your meter Leeds along the circuit end to end checking all wires involved and connections. I create all my own curriculum for training so I could share a image of the voltage drop exercise sheet we use in the lab if it would be helpful.

[Rodger Brandstatter]

It’s been a while since I worked on the starter issue but I’m sure that I had full voltage on the wire from the relay when it was lifted from the solenoid while pushing the starter button. There was only a voltage drop when it was connected and cranking the engine. I did have full voltage at the terminal strip behind the headlight downstream of the starter button. The battery is new and fully charged. I could probably get the relay and wiring out where I could get at it and partially disconnect the modular plug where I could get my voltage meter lead on the exposed male spade terminals of the relay and with an assistant pushing the starter button trace the voltage drop. I’d like to see the exercise sheet if it’s not too much trouble dukekleman. Thanks.

[Lyle Manheimer]

A voltage drop when cranking the engine is normal but not to 7 volts!!!! You are using a high current starter. Are you using an upgraded battery with more CCA , cold cranking amps?? Keep in mind your little can relay is rated to operate at 12 volts, it will not operate at 7. This is also true of the solenoid. I think you better start over by putting your meter on the battery TERMINALS and crank the engine with either the OEM system or your improvised heavy duty momentary switch. If your battery terminal voltage is dropping to 7!!! volts look at the primary starting system not the control circuit. Just because the battery is new does not mean it is up to the task with an upgraded starter. Let us know and be careful of burning the midnight oil!!!

[dukekleman]

Rodger,
Here's a work sheet that should help you locate your problem. I created it to be used in lab testing. Hopefully it makes sense and helps!

Voltage Drop Assignment.docx

[Lyle Manheimer]

Nice chart to work with Duke. I think this is the way for Rodger to identify what is really going on.