• Ciao Guest - You’ve landed at the ultimate Guzzi site. NEW FORUM REGISTRATIONS REQUIRE EMAIL ACTIVATION - CHECK YOUR SPAM FOLDER - Use the CONTACT above if you need help. New to the forum? For all new members, we require ONE post in the Introductions section at the bottom, in order to post in most of the other sections. ALWAYS TRY A SEARCH BEFORE STARTING A NEW TOPIC - Most questions you may have, have likely been already answered. DON'T BE A DRIVE-BY POSTER: As a common courtesy, check back in and reply within 24 hours, or your post will be deleted. Note there's decades of heavily experienced Guzzi professionals on this site, all whom happily give endless amounts of their VALUABLE time for free; BE COURTEOUS AND RESPECTFUL!
  • Be sure to see the GTM STORE link also above for our 700+ product inventory, including OEM parts and many of our 100% Made-in-SoCal-USA GTM products and engine kits. In SoCal? Click the SERVICE tab above for the best in service, tires, tuning and installation of our products or custom work, and don't miss our GT MotoCycles® (not) art on the BUILDS tab above. WE'RE HERE ONLINE ONLY - NO PHONE CALLS MADE OR RECEIVED - DO NOT EMAIL AND ASK QUESTIONS OR ASK TO CALL YOU.
  • There is ZERO tolerance on personal attacks and ANY HYPERLINKS to PRODUCT(S) or other competing website(s), including personal pages, social media or other Forums. This ALSO INCLUDES ECU DIAGnostic software, questions and mapping. We work very hard to offer commercially supported products and to keep info relevant here. First offense is a note, second is a warning, third time will get you banned from the site. We don't have the time to chase repeat (and ignorant) offenders. This is NOT a social media platform; It's an ad-free, privately funded website, in small help with user donations. Be sure to see the GTM STORE link above; ALL product purchases help support the site, or you can upgrade your Forum profile or DONATE via the link above.

Troubleshooting circuits

john zibell

john zibell

Moderator
Staff member
GT di Razza Pura
Joined
Oct 28, 2008
Messages
10,536
Reaction score
2,534
Location
Huntsville, AL
I've seen may requests for help with circuits. Several years ago I wrote an article for a magazine on a basic system for finding faults. Hopefully with this basic instruction and help from Carl Allison's schematics,https://www.guzzitech.com/forums/resources/categories/wiring.16/ , you will be able to locate the gremlins.
 

Attachments

Last edited:
Good advice. One issue I would warn about would be using a voltmeter or multimeter to measure voltages. Because of the high input impedance of these devices, they tend to find "phantom voltages" which may disappear when any load is applied.

I prefer the light bult (low wattage) tester, especially those that can penetrate insulation. They don't tell so many lies. :lol:
 
kiwi dave wrote:
Good advice. One issue I would warn about would be using a voltmeter or multimeter to measure voltages. Because of the high input impedance of these devices, they tend to find "phantom voltages" which may disappear when any load is applied.

I prefer the light bult (low wattage) tester, especially those that can penetrate insulation. They don't tell so many lies. :lol:
Click to expand...

Yes a test light is good for tracing 12 volts, but if it is a control circuit, say 5 volts like the TPS supplied voltage, the light may not light.
 
Also a control circuit is likely to be a high impedance load anyway, so putting a low impedance light across it will load the circuit to the point that it definitely won't work.
Correctly used, a voltmeter will give a lot of information, but always check voltages under load.
By this I mean, if a light is dim, don't disconnect it before measuring the voltage. If you do, then you will not be able to find a high resistance joint.
Remember, you can also use a voltmeter to check voltage drop along a cable.
 
Re: Re:Troubleshooting circuits

kiwi dave said:
Good advice. One issue I would warn about would be using a voltmeter or multimeter to measure voltages. Because of the high input impedance of these devices, they tend to find "phantom voltages" which may disappear when any load is applied.

I prefer the light bult (low wattage) tester, especially those that can penetrate insulation. They don't tell so many lies. :lol:
Click to expand...


I carry a 12 volt bulb with wires soldered to it and clips on the end for this very reason. I have seen too many people mistake a poor high impedance connection for a good connection because they use a fancy digital meter that isn't loading the circuit.

Plus the light bulb can come in handy along the road at night as a trouble light. :laugh:

Not very useful for setting a TPS, but great for most other things.
 
As a retired (retarded?) Telephone Switch Maintainer who went from tin cans and strings to fiber optics over a 41 year career I feel that I can say that there is nothing better than using a simple "bug lamp" or trouble shooting lamp for most things where electronics are not involved. I emphasized the electronics part as we do not wish to blow any diodes or chips in the circuit.
A dim bulb can say a lot if there is a poor connection and will help you find trouble when it is easy to wiggle wires and connections while looking for changes. A digital multimeter will have numbers rolling all over the place and will be impossible to read, an analog multimeter will at least show trends up or down.
An over bright bulb obviously will demonstrate excess voltages.
There is a term called step by step trouble shooting meaning that you can break down each questionable section to help isolate the problem. Chasing a problem through a multi story building with no elevator is different than a bike, but the same idea applies. My wife tells me that there is a French expression that says, "if you don't have good brains, than you better have good legs". I have good legs. :laugh:
A nice sharp almost needle like probe on the end of a lead is good for poking into wires and minimizing any damage that a chunky stock multimeter probe may cause.
 
William C. Myers said:
John Zibell,
Do you have a favorite book(s) or recmommendation on "books on basic circuits'?

William
Click to expand...


William, I'm afraid I don't have a recommendation for you. What I relayed is what I was taught going through a missile maintainer course at Redstone Arsenal. It was part of the training I received to be a technical writer on missile systems.
 
You must log in or register to reply here.
Back
Top