Ironhead Electrical issue

[brucstoudt]

Originally Posted by Ferrous Head

At the very least, jumper leads with a good battery. Check that the lights work.

i use a battery charger for that set at the lowest amp setting.my'60 XLCH doesn't have a battery,so i use that to test the lighting circuit without kick starting the stroker motor.

[BigMek]

This got really long-winded, but the TL;DR is it's good to take things slow when diagnosing electrical problems. Test one thing at a time and try to narrow down the problem as much as possible.


If your test probe is lighting between battery negative and the frame/engine, that means you have a completed circuit somewhere. This is written assuming you have a multimeter that can measure resistance because it will give more specific results than a test probe.

Question for the points experts - if they're closed, could that show up like a short with the key off? Assuming the bike still has points of course.

To find your completed circuit, start by removing the battery, then disconnect the wires that connect the breakers to the key switch. Make sure the key switch is off and measure the resistance between each pair of either the terminals or the wires connected to them (it will take three separate measurements). If any of them come up zero your key switch is toast.

Next, check the resistance between each circuit breaker and ground. That will tell you which breaker is the problem. Then you can start removing wires from that breaker and testing each one's resistance to ground - If any of them come up zero, you've found a short to ground that needs to be fixed.

If you find any shorts, turn off any switches or unplug any connectors in the circuit and see which end of the circuit is the problem (upstream or downstream of the switch/connector). That should narrow down the trouble spot to a single run of wire, which you should then inspect closely for broken insulation, crushes, pinches, etc.

75 stock wiring diagram on the Sportsterpedia: http://sportsterpedia.com/doku.php/t...#sportster_xl1

[Ferrous Head]

Question for the points experts - if they're closed, could that show up like a short with the key off? Assuming the bike still has points of course.

Nope.

With the key off there should be no current flowing through the pints. If that happened the coil will be energized and most likely get so hoot it fails.

[einheit 13]

Ok, I’ve been super busy with work so I haven’t messed with it much. The only thing hooked up on the battery is the positive cable and another wire that I haven’t traced. Nothing is attached to the negative side of the battery. Clip the probe to the negative post on the battery, everything but the tires and cable makes the probe light up. It had a Dyna S ignition unit. The only circuit breaker is from the electronic regulator off the generator. Both the A and F on the generator make it light up. Same with both sides of the coil. If you turn the key on, the test light gets brighter. I’m using the test light as a ground. And again, when you hook the negative cable to the battery, all power goes away.. Everything goes to the starter solenoid. Im gonna have to disconnect everything and make individual circuits. It can only be the starter solenoid, key switch, or the generator. That’s my line of thinking. He says the generator was replaced last year. The bike was running and just stopped running one day.

[BigMek]

The test light getting brighter with the key on is the expected behavior if you have a short (without a short the light should be off until you turn on the key). More things are drawing current, which means more current through the probe and a brighter light. The probe turning off with the negative cable connected is also the expected behavior. The negative cable has much lower resistance than the probe, so most of the current is going around the probe instead of through it and there's not enough to light it up.

There should only be one wire on the battery positive terminal according to the factory wiring diagram. Stock, a 75 should have three circuit breakers under the seat (http://sportsterpedia.com/doku.php/t...rcuit_breakers).

Based on the service bulletin for the 1119600 voltage regulators (http://sportsterpedia.com/lib/exe/fe...-_7-1-1960.pdf), you should see 12 volts from Bat to both Gen and Field and 0 volts from Gen and Field to Ground when the generator isn't spinning. Using a test light, it should light when connected between Bat and battery negative, but NOT between battery negative and Gen or Field. If it does, that means your cutout relay is probably stuck shut - remove the wire from the Bat terminal on the regulator and see if the test probe still lights up when connected between battery negative and ground.

[einheit 13]

Got it figured out…ever seen a battery reverse polarity? This one did.

[IXL2Relax]

Well - I often give the advice to check the battery, cables, voltages & grounds as a FIRST STEP for any Electrical Problems, thereby making sure all the basic stuff is working properly. But some people feel that basic preventative maintenance actions are wasted when trying to track down a problem.

Sounds like I should have given that advice here...

When you're having issues with the electrical system, use this Sportsterpedia section about
checking the battery cables, voltages and grounds - DO THIS AS MAINTENACE, TOO:
http://sportsterpedia.com/doku.php/t...place_to_start

IXL _______ >>>> My Motorcycle Chronicles Are Here <<<<
For Sportster Tech Info:
Ride On The Sportsterpedia - A Toll-Free XLForum Information Highway!

[Ferrous Head]

Originally Posted by einheit 13

Got it figured out…ever seen a battery reverse polarity? This one did.

Yes, they can reverse their polarity. But only by discharging the battery and then charging it up incorrectly using an old style charger. The new ones detect reversed polarity and protect against it.

There is another case when this can happen but only when you have two batteries in series.

Sp, more than likely you had a dead short somewhere on the bike.

You checked for current, but not for voltage. Had you dropped a multi-meter on the components you were testing OR the battery itself you would have seen negative voltage where it should have been positive.

First point of call when troubleshooting electrical problems on your bike is to check the voltage at the battery. Anything below 12.5 volts positive and it probably needs a charge.

They make really nice charging units now. Some include a desulphating stage to help keep your battery in shape. Virtually any new charger will detect of you hook the leads up the wrong way and tell you.

A $50 multi meter and a $50 battery charger will cost you $100 or 10 hours of your laboue/time.. (Or in my case 200 hours as my time is only worth 50 cents and hour now.)

[einheit 13]

Originally Posted by Ferrous Head

Yes, they can reverse their polarity. But only by discharging the battery and then charging it up incorrectly using an old style charger. The new ones detect reversed polarity and protect against it.

There is another case when this can happen but only when you have two batteries in series.

Sp, more than likely you had a dead short somewhere on the bike.

You checked for current, but not for voltage. Had you dropped a multi-meter on the components you were testing OR the battery itself you would have seen negative voltage where it should have been positive.

First point of call when troubleshooting electrical problems on your bike is to check the voltage at the battery. Anything below 12.5 volts positive and it probably needs a charge.

They make really nice charging units now. Some include a desulphating stage to help keep your battery in shape. Virtually any new charger will detect of you hook the leads up the wrong way and tell you.

A $50 multi meter and a $50 battery charger will cost you $100 or 10 hours of your laboue/time.. (Or in my case 200 hours as my time is only worth 50 cents and hour now.)

All the wiring checked out. As did the starter and generator and rectifier. Super weird, the multi meter showed nothing but 12.51-12.92v. The trickle charger never showed a wrong connection. It would restart itself if I hooked up the negative terminal. Never showed a ‘wrong’ connection and I only have the ‘old style’ charger because it’s a brute and is like 40yo. I think the issue is inside the battery itself. It will take a charge just fine when hooked up to a charger. Just wouldn’t power the bike and got that backwards ‘positive ground’ condition. I made some extensions and swapped the cables and the bike powered up. So I went and bought a new battery, threw it in and everything works like it should. Did I mention that I hate working on electrical things…�� thanks for the help guys, really appreciate it!

[Ferrous Head]

Might be time for a new charger as well.

These are small batteries and don't require 50 amp hour chargers. The new chargers will adjust the rate saving your battery from damage. Charge them at an "optimum" rate. And won't start charging if you hook them up wrong.