Winning tip: Hot or cold?

Jan. 1, 2020
The winning tip for November comes from L. Scott Walker of Austin, Texas, and will keep your temperature in line.

This month's winning tip reminds us that temperature matters

Mitchell 1 tech tips automotive aftermarket vehicle repair tips technician tips L. Scott Walker started his tech career in 1992 after graduating from the St. Phillips College in San Antonio, Texas, with an AAS degree in automotive technology. He started working at Mercedes Benz of Austin in 1999 and has been there since. In addition to fixing Mercedes, he also is an adjunct professor of automotive technology at the Austin Community College. While his tip is Mercedes related, it applies equally well to other makes.

"Sometimes a hot 'no start' can be caused by a failure in the crankshaft position sensor (CKP) and not set any related trouble codes in the engine control module. The car will start and run fine after the sensor cools. I check the sensor by removing it from the car, attaching my ohmmeter and then heating it up with a heat gun while watching the meter. If the sensor is bad, resistance will rise and possibly even go 'open.'"

This tip applies not only to CKP sensors, but to any electrical winding on the car like camshaft position sensors (CMP), EVAP purge valves and fuel injectors. You can test the latter by this method, or by activating them repeatedly with a scan tool or multimeter. Information on using your multimeter as a bi-directional control is available online in the AutoPro Workshop.


Avoiding Stripping Plugs

When replacing a set of ignition wires, I like to save the spark plug end boot from a few of the old wires. The longer ones work the best. When replacing the plugs in vehicles with hard to reach or recessed plugs, simply insert the new spark plug into the boot and turn in by hand. This works well even on tight angles, since the boots will allow for flexing around the corners. Torque the plug to spec to finish the installation.

Dave Stierle, New Jersey

Get Direction

One good way to locate a shorted wire is to get a manual compass and trace the harness with it. Current flow creates its own magnetic field and the compass needle will spin erratically near the area of the short.

Jesus Reyes, Texas

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