FORUMS! / Articles / SAFETY / Keep BAT Alive! / Help / About Us
Navigation Home Disclaimer Links & Technical Our Links Scanner & Program info Technical Index Timing Belt Interval Manufacturer's List Small Block Chevy Info Misc. Technical info Auto A/C Tools Trouble Codes Acura Alfa Romeo Audi BMW Cadillac Chrysler Daihatsu Eagle Ford GM GM Import Honda Hyundai Infiniti Isuzu Kia Land Rover Lexus Mazda Mercedes Mitsubishi Neon Nissan OBD2 Peugeot Porsche Saab Saturn Subaru Suzuki Toyota Volvo Volkswagen Yugo
Get an AlldataDIY Repair Info Subscription Special Thanks To: AC Kits.com/AutoACforum.com

Checking Intermittant Electrical Problems

by Jud Hildebrant

    Just about everybody in service/repair industries has had to deal with intermittants (intermittant is used as a noun here) at one time or another, and has lost money and/or spent a lot of time on the repair. Electronics Technicians have worked out a few techniques for dealing with these problems, and I would like to pass along a few of those ideas to you.

Intermittants seem to fall under 2 broad categories:

• Mechanical Intermittants (a problem which appears from motion).
• Thermal Intermittants (Problems which appear or disappear with a change in ambient temperature).

    For mechanical intermittants, the Wiggle Test is the most effective. Wiggle every wire related to the suspect circuit, push and pull on each wire in each connector, tap suspect assemblies firmly with a screwdriver handle, flex every inch of a wiring harness, and examine the internals of each plug-jack connector.
    The components which are most likely to fail are those which are subject to the most vibration, and those which are subject to the harshest environment, which leads to corrosion. For example, battery terminals need to be cleaned periodically, because they are subject to a light sulfuric acid vapor atmosphere. Braided ground straps almost always fail from these factors.

    Thermal intermittants are slightly more predictable. A failure occurs as the temperature rises or falls. Electronic techs have 2 tools for troubleshooting thermals. The first (laugh if you want to) is an ordinary hand-held hair dryer. Use it to add heat to a suspected component, and watch for a premature change failure.
    The second tool is Freeze Spray. This is a spray can that contains a combination of chemicals which have an extremely high evaporation rate, thus dramatically cooling whatever it hits. Freeze spray is available at Radio Shack, and from most electronic supply stores. This is THE thing for troubleshooting, say, a car which quits after a few minutes of driving.
    Keep your freeze spray away from youngsters, however. The nature of the stuff seems to invite horseplay. For example, directing the spray down the back of your wifes' too-tight blue jeans will result in a reaction which I would rather not discuss at this time.(Read and follow all instruction on the product)

    One final note about troubleshootong intermittants; It does no good to test components if the car is not acting up at the time. If the car is behaving normally, then anything you test MUST, by its' nature, test GOOD. It's a harsh fact of life among electronics troubleshooters that a part can test OK, but fail in actual operation. This is because a tester tests with only a TINY amount of power, but the component fails only under the stress of higher voltage and current. 

   Regarding the stresses on electrical/electronic devices, the components which are most likely to develop mechanical intermittants are electro-mechanical devices, such as MAP sensors and TPS potentiometers. The components most likely to develop thermal intermittants are those which contain semiconductors, such as ignition modules and voltage regulators.

    One final note: Educating your customers about the nature and unpredictability of intermittants (before you do any repairs) will help to gain his trust and understanding if your first repair isn't the correct fix.

Best Wishes to all,
Jud Hildebrant

batauto.com©June 2001