Snap-On UHR Ultra, Service Manual

Page: 49 / 84

47
Diagnostics
RACK CHECK
This test checks how coplanar (parallel) the rack is. Even
though we are very resistant to rack problems, non copla-
nar racks can introduce some error to our system.
The image aligner is designed to
perform a perfect alignment every
time. The levelness of the rack “side-
to-side” or “front-to-rear” is irrelevant
to performing this perfect alignment,
however a rack that is non coplanar
(parallel) will induce erroneous read-
ings because the suspension of the
vehicle is under stress.
NOTE: This test is not available when aligner is equipped with 3d or xd targets.
A Non Coplanar rack is evident when one runway is tipped up or down relative to the opposite runway.
• This test checks how coplanar (parallel) the rack is. Even though we are very resistant to rack prob-
lems, non coplanar racks can introduce some error to our system.
• If the lag between rails is less then 0.02 inches (0.5 mm), the rack is considered to be coplanar.
• If the lag is greater then 0.02 inches and less then 0.3 inches we display the value but leave it up to the
individual shop to decide what to do. Although this will not cause a great deal of problems is will affect
the alignment readings a small amount.
•
If the lag is over 0.3 (7.5 mm) inches we tell the user to adjust the rack to the manufacturers specifica
-
tions as this will affect alignment accuracy.
This test requires the use of the RCP fixture. The technician must have this fixture to check the rack rails for
a coplanar (parallel) condition.
5.
Place the RCP fixture across the rack with the small target on the RF turntable and the large target on the
LF turntable and press “OK”.
6.
Move the RCP fixture towards the rear of the rack just FORWARD of the rear slip plates.
7. Read the results.
Click on “OK” or “Cancel” to exit this test.