Glossary “underinflation” Definition:
Condition with respect to tire inflation that decreases the rolling diameter and increases the contact area, which results in excessive sidewall flexing and tread wear causing excessive heat buildup, ultimately leading to severe tire damage.
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under vehicle lubrication services
Glossary “under vehicle lubrication services” Definition:
Work performed under the vehicle during a chassis lubrication such as changing oil and filter, checking or changing transmission fluid, and gear oil or differential gear oil, lubricating the suspension and steering system, universal joints, clutch ans/or transmission linkage, front-wheel bearings, and inspection of safety-related items.
undercarriage
Glossary “undercarriage” Definition:
The chassis of a vehicle.
undercharge
Glossary “undercharge” Definition:
A/C system operating with a refrigerant charge that is less than specification.
undercoat
Glossary “undercoat” Definition:
Any of several types of paint materials that are applied before the basecoat or colorcoat, such as primers, sealers, etc. Also applies to the application of a tak like material that is sprayed onto the undercoat to provide corrosion protection, but also has some sound damping qualities.
under tone
Glossary “under tone” Definition:
The color produced by a tinting base when it is mixed with white or aluminum.
under dash unit
Glossary “under dash unit” Definition:
Term used for hang on unit such as for a CB radio or other aftermarket accessory.
under drive
Glossary “under drive” Definition:
Condition wherein a planetary gear set is in reduction, delivering a lower speed, but higher torque and more power at its output.
under hood lubrication services
Glossary “under hood lubrication services” Definition:
The work performed under the hood during a chassis lubrication such as lubricating the distributor, manifold heat-control valve, upper suspension, hood hinges and latch, checking the fluid in the engine crankcase, brake master cylinder, radiator, battery, and power steering reservoir, plus inspecting belts and safety-related items.
ultraviolet screener
Glossary “ultraviolet screener” Definition:
An ingredient added to paint finishes that is designed to cut off or reduce ultraviolet light penetration into a paint film. This ingredient is needed primarily in metallics and in clears. Provides durability to paint.
umbrella seal
Glossary “umbrella seal” Definition:
An umbrella-shaped valve stem seal used to direct oil away from the stem and guide.
unburned hydrocarbons
Glossary “unburned hydrocarbons” Definition:
HC is a major pollutant in exhaust gases as a result of the partially unburned fuel after combustion.
UNC
Glossary “UNC” Definition:
Unified National Coarse. Identifying a standard thread pitch and count.
ultraviolet
Glossary “ultraviolet” Definition:
An invisible spectrum with wavelengths shorter than visible light b longer than X-rays about 200 to 4000 angstrom units.
ultraviolet light
Glossary “ultraviolet light” Definition:
Light source used in non-destructive testing for cracks in metal parts. Also used to detect fluid leaks, by using special dyes that are illuminated in the present of UV.
ULEV
Glossary “ULEV” Definition:
Ultra Low Emission Vehicle
ultrahigh frequency (UHF)
Glossary “ultrahigh frequency (UHF)” Definition:
Band of signal frequencies falling between 300 and 3000 MHz.
ultrasonic leak detector
Glossary “ultrasonic leak detector” Definition:
Diagnostic tool that consists of a high frequency generator (tone generator) and receiver. The frequenct generator is placed inside a closed vehicle. The receiver detects the frequencies that escape through gaps and leaks in door and window seals. Receiver, can be used by itself to detect vacuum leaks.
UIM
Glossary “UIM” Definition:
Universal Ignition Module
U-joint
Glossary “U-joint” Definition:
Term for universal joint.