Electrical Troubleshoot. NO POWER?!

[jlew]

1980 CB750 DOHC

rode out to get some items last night and parked in the garage and shutdown about 10pm (key off, switch off, petcock off)

6am this morning i go to start up, nothing. No indicator lights, no power at all.
threw tender on it and i get blinking red light (indicating not charging battery)

red flashing means the microprocessor is getting AC power but it is not supplied to the battery either because of a weak connection or voltage too low on the battery.

i brushed my terminals and redid the connections but still flashing red.

the battery is 2 seasons old and gets the tender when i'm away for a few days or if i've had an abundance of low rpm 'in town' riding (however 99% of my riding is freeway 7-8k rpm range)

battery toasted?
anyone have a step - by - step checklist to diagnose?

 

[PATMAN750]

I would crack out the old voltmeter and start taking some measurements. I'd figure out if your bikes charging system is working by testing the rotor resistance, stator connectivity, voltage to the alternator, voltage from the alternator a various RPM (at the alternator, at the regulator/rectifier, and at the battery terminals. I believe you want to read about 13.6 or so volts at the battery at cruising RPM to ensure good charging.

I'd also check to see if the battery is still good. So I'd see how many volts your battery is reading right now. Here is a fancy little chart to relate voltage to charge %, http://www.marxrv.com/12volt/voltchart1.gif. I think an autoshop (advanced auto parts, pep boys, etc) might be able to test your battery's health and ability to hold charge as well.

If everything there looks okay, then I'd check the bikes wiring and make sure that there is no incorrect connection that would be using the battery when all the switches are set to off. I might have a wiring diagram for your bike if you need it.

That's what I'd do at least. It might be laborious for some, but I think it's good to be thorough. Good luck!

 

[jlew]

been at it for a few hours, had to shampoo my carpets first... Happy Fathers Day Dads!

So my multimeter was doing some seriously funky things (no probes plugged in, random numbers displaying and changing every second or so.) so i tossed it. pulled out my other one, which is beefy but not built for automotive (its household so it rounds the numbers)

pulled battery. no reading across the terminals lol. put on my automotive charger @ 12v 6amp and let it sit all day, i'm now getting a 13v reading (remember el sucko meter is rounding) so i could be 12.8 or 13.2 or whatever but i'm calling that a fully charged battery.

So i put the battery back in and WTF?! my lights turned on... but i don't have the key in the ignition, and the kill switch is turned to off??? So I put key in and toggled on/off and lights shut off. Faulty ignition something or other?

At this point the battery is back in the bike and back on the tender (tender light pattern shows 'monitoring' state). But when i put the key in I do not get any lights, no indicators or headlight and no starter activity (no crank or even relay clicking). battery showing 14/15v with tender plugged in (again rounded)

I've checked fuses on the tree and main fuse near battery and all are still good.

not having any power to even the indicator lights when i turn the key on would lead me to think a shot battery or something with the ignition. I have the Honda service manual in PDF. i'm going to stare at the wiring diagram on my phone and go fix the kids dinner; if anyone has any tips on what to check when toggling the key on/off to check for shorts that would help greatly

 

[Redbird]

Sounds like the key switch is bad/shorting. If the switch shorted and turned the headlight on, that could be why it killed the battery overnight.

 

[jlew]

Took the ignition switch out, cleaned up contacts and checked continuity.

Lock: none across any terminal
Off: none across any terminal
On: across batt and ignition posts and tl1 and tl2 (br and br/w I believe these are dash lights and tail lights)
Park: across batt and p post (parking lights)

I ran jumpers to my leads and shook the shit outta the switch while off to see if I could get something to beep but nothing.

So at a high level check my switch seems to check out right? However after install I still get no power to indicator lights or start button when key is switched on as well as the voltage at the battery drops from 14 to immeasurable when I turn on the key. And back to 11ish when I turn the switch back off.


Sent from my ADR6300 using Tapatalk 2

 

[Hoosier Daddy]

I still get no power to indicator lights or start button when key is switched on as well as the voltage at the battery drops from 14 to immeasurable when I turn on the key. And back to 11ish when I turn the switch back off.

That right there sounds like a bad battery, can't hold up to any kind of load...
Did you have the meter on it to see how far the voltage dropped when you turned the key on?

 

[jlew]

Yeah when I turn key it drops to basically zero then back to 12-13 when I turn it off.
I was thinking since no fuses are blown its a bad battery or dead short on a non fused cicuit through the switch. I'll hafta look at the schematic but I think the starter relay and starter circuit.. might check that next if the battery checks out fine at the battery store today

Sent from my ADR6300 using Tapatalk 2