Electrical issue

WEM

Joined
Dec 8, 2017
Messages
65
Country flag
I have a 1974 Commando. Bike is (was) running well with no issues. I pulled into the driveway after a short ride to run some errands and was just about to turn the bike off when it died. That has never happened before. The bike had been stopped and started twice with no issues during my ride. Removed the left side cover to check battery voltage with multimeter and noticed that one end of the plastic inline fuse holder had partially melted! I thought that the connections in the fuse holder, which is pretty old, might have corroded resulting in a poor connection and heat build up. I purchased a new plastic inline fuse holder and a new package of 20 amp SEF fuses. I replaced the melted inline plastic fuse holder with the new one, installed a new 20 A SEF fuse, and turned the key to start position. Lights and horn worked. Bike started on first kick, ran for 3 or 4 seconds then died. The new fuse had blown. Replaced the fuse with another 20 A SEF fuse, but from a different manufacturer. Lights and horn worked, bike started briefly again and then died. However, it was not visually obvious that the different style of fuse had blown so I checked it with voltmeter and got continuity across the fuse but no horn or lights on bike. Went back to the original type fuse. Same deal. Lights and horn worked, bike started right up, ran about 5 seconds and died. Fuse had blown. It looks like even though both types of fuse are labelled 20 A SEF, one might be a bit more robust than the other? I'm not sure what the heck is going on but before I start working through the system, any hints or advice that might narrow the search would be greatly appreciated. The bike has stock points ignition system and has a Podtronics Rec/Reg.
 

RoadScholar

VIP MEMBER
Joined
Dec 28, 2008
Messages
1,556
Country flag
Does this happen when the handlebars are turned?

Have you done an in-depth look at the harness?

Not to say that this isn't going to get involved/expensive, but look for the simple problem(s) first. If you start chasing the Cheshire Cat you'll greatly increase the time it takes to get back to Kansas...

Best.
 

gtiller

VIP MEMBER
Joined
Nov 5, 2012
Messages
999
Country flag
A melted fuse holder and now your new fuse holder is blowing fuses...
Sounds like something on the bike is shorting out, and your fuses are/have been doing their job.


Start with looking for pinched wires under the tank, around the coils and the handlebar switches.

Is your reg/rec a new addition? Could there be an issue with the wiring in this area do you think?
 

WEM

Joined
Dec 8, 2017
Messages
65
Country flag
A melted fuse holder and now your new fuse holder is blowing fuses...
Sounds like something on the bike is shorting out, and your fuses are/have been doing their job.


Start with looking for pinched wires under the tank, around the coils and the handlebar switches.

Is your reg/rec a new addition? Could there be an issue with the wiring in this area do you think?
Thanks for the replies. The reg/rec is two years old. I started looking at the tail light fairing, mainly because the left turn signal, which is a cheap aftermarket item, has been occasionally intermittent. Pulled the fairing. All connections looked tight and clean. Then I checked the handlebar cluster. Connections looked good but the kill switch seemed a little stiff. The switch clusters are 46 year old OEM. Might be time for new ones. Pushed the kill button several times and it seemed to loosen slightly. I can't recall the last time I pushed the kill switch button. I then checked the reg/rec connections. Again, all connections looked clean and tight. Then pulled the headlight apart. All connections in there were also clean and tight except for a slightly loose ground to the shell. Connection was not falling off loose, but could be wiggled. Tightened that connection. Then checked the ground connection where the old zener connected to the right z-plate. The connection was pretty dirty. Cleaned it up and sanded the brass connecting ring clean. While doing that I noticed that I had installed the accessory plug located in front of the right z-plate upside down when I rebuilt the bike several years ago. I had reinstalled the plug with the opening for the wires pointing up. When I pulled the plug off, the housing was full of oil/water/dirt. Cleaned it up and reinstalled the housing with the opening pointing down. Then just before I called it a day I figured I'd give it another shot. Bike fired right up and stayed running with nice steady idle for about 10 minutes until I shut it down. Not sure if it was the loose ground in the headlight shell, the oil/water/dirt mixture packed in the accessory plug housing or the stiff kill button but problem seems to be fixed? I'll try again tomorrow morning to see how things go. In the meantime, any recommendations for a good product to clean electrical connections in the switch clusters. Thanks.
 

gtiller

VIP MEMBER
Joined
Nov 5, 2012
Messages
999
Country flag
You can get a rebuild kit for the switches - available with long or short flippers with or without the red button.

Here's an example:



I also use a fibreglass pencil for cleaning up contacts - they are very inexpensive amd a useful thing to have in your toolbox.

A2C4949E-DBD2-4595-9D97-A8AD7D61B2C3.jpeg
 

L.A.B.

Moderator
VIP MEMBER
Joined
Nov 20, 2004
Messages
15,886
Country flag
Then pulled the headlight apart. All connections in there were also clean and tight except for a slightly loose ground to the shell.
Not sure if it was the loose ground in the headlight shell,

A loose 'ground' there is unlikely to be the cause a fuse blowing, also, the wire connection to the headlamp shell is not a headlamp 'ground' but a return connection (to harness red) for the front direction indicators.

Then checked the ground connection where the old zener connected to the right z-plate. The connection was pretty dirty.

That red wire is also not a 'ground' but a return for the Zener diode so if the Zener isn't fitted then the red wire is redundant.
 

maylar

VIP MEMBER
Joined
May 13, 2007
Messages
3,167
Country flag
I chased a short circuit gremlin for about a year. Intermittently and randomly would blow a main fuse. Turned out to be the blinker switch (Sparx replacement) would sometimes short to the housing, which was grounded through the handlebars.
 

WEM

Joined
Dec 8, 2017
Messages
65
Country flag
Thanks to everyone for their suggestions. After some troubleshooting work yesterday, when I left it last night, after a new fuse holder replaced the one that had melted, the bike was idling nicely until I turned it off for the night. Everything seemed good. I didn't get a chance to take it for a test run until today. Bike fired right up this morning, idled nicely. But I noticed that the WLA red warning light, which came on as usual when ignition was turned on, would stay on after bike started until revs reached over 1000 rpm or so. The light would then go off until the revs dropped back down to around 1000. I repeated start up several times. Same scenario each time. This has never happened before. Not sure if this is related to the original issue or is a new issue. I'm not a big believer in coincidence but it might be possible that the two issues, melted fuse holder and WLA staying on after start, are not related. Any suggestions?
In any event, went for a short 5 minute ride around the neighbourhood staying close to home. No problems. Got home turned bike off and had a look at the fuse holder. No problems. Wasn't warm to the touch. Everything looked good. Took second ride around the neighbourhood. After 2 or 3 minutes, bike started to sputter and died. I was close to home and managed to push bike home. I remember it being easier fourty years ago. When I pulled side cover, I could see that the new fuse holder had melted! Pulled fuse holder off bike, scraped off melted plastic and got fuse out. Fuse looked good. Tested fuse for continuity and got continuity. 20 amp SEF fuse hadn't blown but second fuse holder had melted. I would think that the fuse should blow before the kind of heat need to melt the fuse holder developed? Again, any suggestions regarding what is going on here? Thanks.
 

gtiller

VIP MEMBER
Joined
Nov 5, 2012
Messages
999
Country flag
That is actually how it should be!
Typically at idle, the bike will draw a little more power than the alternator is producing.
The warning light assimilator will flicker the lamp at a low idle, and it should go out as you raise the revs above idle.
I wonder if your cleaning and reseating of connectors has reconnected things to how they should be!


The fact your fuse holder is melting, and the fuse isn’t blowing is setting off the alarm bells.
Your fuse should be the weakest link, and at the moment it isn’t.


Tell us about your charging system,
With things melting like they are, I would usually start with the Zener diode as it sounds like you have an over voltage issue. However, you say you are running a combined reg/rec now.

I think it is worth starting your investigations in this area.
Take it off the bike, and test it out, it’s a variable you can rule it in just a few minutes.

Follow this guide to testing it:

Then let’s go from there.
 

WEM

Joined
Dec 8, 2017
Messages
65
Country flag
That is actually how it should be!
Typically at idle, the bike will draw a little more power than the alternator is producing.
The warning light assimilator will flicker the lamp at a low idle, and it should go out as you raise the revs above idle.
I wonder if your cleaning and reseating of connectors has reconnected things to how they should be!


The fact your fuse holder is melting, and the fuse isn’t blowing is setting off the alarm bells.
Your fuse should be the weakest link, and at the moment it isn’t.


Tell us about your charging system,
With things melting like they are, I would usually start with the Zener diode as it sounds like you have an over voltage issue. However, you say you are running a combined reg/rec now.

I think it is worth starting your investigations in this area.
Take it off the bike, and test it out, it’s a variable you can rule it in just a few minutes.

Follow this guide to testing it:

Then let’s go from there.
Thanks for the direction I'll report back ASAP
 

WEM

Joined
Dec 8, 2017
Messages
65
Country flag
That is actually how it should be!
Typically at idle, the bike will draw a little more power than the alternator is producing.
The warning light assimilator will flicker the lamp at a low idle, and it should go out as you raise the revs above idle.
I wonder if your cleaning and reseating of connectors has reconnected things to how they should be!


The fact your fuse holder is melting, and the fuse isn’t blowing is setting off the alarm bells.
Your fuse should be the weakest link, and at the moment it isn’t.


Tell us about your charging system,
With things melting like they are, I would usually start with the Zener diode as it sounds like you have an over voltage issue. However, you say you are running a combined reg/rec now.

I think it is worth starting your investigations in this area.
Take it off the bike, and test it out, it’s a variable you can rule it in just a few minutes.

Follow this guide to testing it:

Then let’s go from there.
Grant,
I haven't had a chance to run the diagnostic on the Podtronics Reg/Rec yet but I have been looking at some of the information you have kindly provided links for. There is an interesting article entitled, "Exposing the Market Leading Regulator/Rectifier". This article concludes that this type of reg/rec is not kind to alternators, particularly when running with no load. "The less load there is, the bigger the hit on the alternator." I have been actively trying over time to reduce the load on my electrical system. As a rule, I don't ride at night, so no headlight. I also generally don't ride with the headlight on in the day. I have replaced all bulbs, headlight, taillight, brake light, indicators with LEDs to reduce load. Is it possible that I may have inadvertently done some damage to the alternator by not loading it?
 

gortnipper

VIP MEMBER
Joined
Nov 11, 2013
Messages
3,317
Country flag
I had my 74 die a while back, blowing fuses constantly. One of the teminals on the headight toggle switch in the headshell was shorting on an unknown when the headlight was put in, since it would run fine with the headlight out.

I ended up bending the terminals 90 degrees so they were parallel to the road, and this cured it.
 

concours

VIP MEMBER
Joined
Dec 29, 2011
Messages
4,387
Country flag
Follow the clues.
They point to WLA shorted inside.

As previously mentioned, you should be looking for a short, where something is touching ground. Usually a DEVICE, not a wire, unless a doofus had created it (mis-routed, not supported, etc.)
 
Joined
Jan 31, 2010
Messages
2,218
Country flag
I agree the the warning light is functioning more or less normally.

I also agree it's a short of some kind though melting the fuse holder instead of blowing the fuse would indicate the amp rating of the fuse is much too high but I believe the current wisdom is that a 20A (as rated in the USA) is about right (though I ran for many years with a 30A because that's what the owners manual says)! :rolleyes: Did you look at the fuse itself to see the rating as opposed to the box (or whatever) it came in?

One possibility is that there is some connection interference between the fuse and the fuse holder contacts. IF, for example, the spring-loaded contact on the battery side of the fuse holder was making poor contact with the fuse, the increased resistance and subsequent increased current/heat would be within the holder and that current would not pass through the fuse. Seems unlikely this would occur with two different fuse holders but hey,...I'm speculating here. ;)

On one hand, it seems that there are two different problems - excessive current draw by some component and a fuse that doesn't blow with that excessive draw. BUT...a faulty contact at the fuse holder could cause the melting while disguising the problem... Again...speculating...
 
Joined
Feb 10, 2009
Messages
2,122
Country flag
Grant,
I haven't had a chance to run the diagnostic on the Podtronics Reg/Rec yet but I have been looking at some of the information you have kindly provided links for. There is an interesting article entitled, "Exposing the Market Leading Regulator/Rectifier". This article concludes that this type of reg/rec is not kind to alternators, particularly when running with no load. "The less load there is, the bigger the hit on the alternator." I have been actively trying over time to reduce the load on my electrical system. As a rule, I don't ride at night, so no headlight. I also generally don't ride with the headlight on in the day. I have replaced all bulbs, headlight, taillight, brake light, indicators with LEDs to reduce load. Is it possible that I may have inadvertently done some damage to the alternator by not loading it?

Is this the article? The tests don’t appear to involve an alternator.

 
Joined
May 7, 2005
Messages
4,453
Country flag
I run a 15A modern fuse, never blows without a short and provides less chance of burning out the plastic before it does blow. The original fuse has the same rating as a 17.5A fuse, so 20A or 15A are closest.
 

gtiller

VIP MEMBER
Joined
Nov 5, 2012
Messages
999
Country flag
@WEM that article was written by our forum friend @Jeandr
I was pleased to host it on my site, as I am in 100% agreement with his findings.
Jean used AC transformers to mimic the behaviour of an AC alternator, so I believe it stands up in terms of testing the reg/rec.

However, you should be aware that most of the classic bike world LOVE Podtronics, as they are the biggest brand.
...and most people disagree with our findings and viewpoints on short-type regulator rectifiers often dismissing our comments as complete bunkum.


The Podtronics was designed many years ago with the prime goals of low cost and simplicity in mind.
In fact I recall reading Bob Kizer (the original maker, who is sadly no longer with us) commenting back in the day that he wanted to dumb it down so that any idiot could fit one.

It was designed to replace the Zener and Rectifier on a bike, with everything else left as is.
  • So there would be a constant draw of power from the energy consumers on the bike (light bulbs, coil ignition and the occasional toot on the horn)
  • There would be a battery and maybe a capacitor on the other end to store the charge
  • The alternator stator was a standard output one, matched (by the bike manufacturer) to the rest of the electrical system.
  • The primary case was running in a splash of oil to help keep things cool
  • It always was a recommendation to ride with your headlight on all the time, as it helps keep the electrical system in balance (also a plus for safety)
If those parameters are adhered to, there is no problem with running a Podtronics reg/rec or one of the subsequent copies that have emerged on to the market ever since.


However, when you start to disturb that balance you'll start to see issues and ultimately failure.
Things that can upset the balance are:
  • Installing a more powerful alternator stator - you are not using more power, so when you produce more, the excess needs to go somewhere
  • Installing LEDs - you are reducing the power consumption on the bike, so your original alternator is now too high powered
  • Running a magneto - you have just taken out the coil ignition, one of the many power consumer, that was keeping your charging system in balance
  • Running with no battery - you need one to smooth out the power that is being produced - this is a big help to the sensitive electronics we are installing on our bikes these days
... I could go on - but these days I try to be conscious that people get bored and angry when they read my posts.



The way a short-type reg/rec works (the Podtronics type) is to dead short the AC lines coming from your alternator stator when the target voltage of the battery is reached.
Any small amount of excess overvoltage is then shunted to earth in the form of heat.
So when your battery is charged, and that 'gate' is closed, your alternator is running shorted.

stator dead short_s.png

This is a different situation to when you alternator is running under full load - it is designed to do that, and because the load is outside of the alternator windings, the light guage, varnish covered alternator windings will not get damaged.
Basically, the windings in the stator are acting as a fuse in this scenario.
Either, the resin cracks or the insulating coating over the wire inside melts.

stator load_s.png



@WEM I have a hunch that this is not your problem - if you disconnect the two AC wires that go from your alternator stator to the reg/rec and attach a headlight bulb, I have a feeling you will get a decent output and your light bulb will glow at engine idle, and shine brightly when you blip your throttle.

Fusholders melting is a sign of over current and shorting.

We run a 20 amp blade type fuse on the MK3
... on a pre-MK3 there should be no problem at all downsizing to a 15 amp fuse as @kommando states.

fuse.png

An SFE fuse is supposed to be fast acting and is supposed to be automotive rated, so it is really weird that it is not blowing - again an alarm bell there.


Look at the breakdown of power consumers.
This is for a MK3, so ignore the electric start stuff, but everything else is the same.
You are drawing well under 15 amps during normal running even with a standard headlight bulb.

power consumers_s.png
 

maylar

VIP MEMBER
Joined
May 13, 2007
Messages
3,167
Country flag
The fact your fuse holder is melting, and the fuse isn’t blowing is setting off the alarm bells.
Your fuse should be the weakest link, and at the moment it isn’t.

I think that this is the key. Something is drawing enough current to melt the fuse holder, yet it's not a direct short that would blow the fuse.
A Commando should draw less than 10 amps in normal conditions. I think an ammeter test is in order.

BTW, all fuse holders are not created equal. If you're still using a glass 3AG/AGC fuse the leads should be 14 ga. and rated at 30 amps.
 
Top