Hummer H1 Service Manual page 415

6-32 Wheels and Tires/Central Tire Inflation System (CTIS)
CTIS AIR LEAK TROUBLESHOOTING
This section contains troubleshooting information for locating
and correcting air leaks within the Central Tire Inflation Sys-
tem.
WARNING: CTIS air system components are subject
to high pressure. Always relieve air pressure before
loosening or removing air system component(s) by dis-
connecting the quick-disconnect valve assemblies at
each wheel end. Failure to follow this warning may re-
sult in serious personal injury.
CTIS Troubleshooting Checklist
1. Fill all tires to at least 40 psi (270 kPa) using the on-board
compressor or shop air source.
2. Note the needle positions on the air gauge. If the needles
are not even, line them up by inflating the lower pressure
tires. Then return the inflate/deflate switch to OFF.
NOTE: The tires are isolated from the rest of the system so
that the areas between the compressor selector valve and
geared hubs and selector valve can be isolated and checked.
3. Isolate each tire and wheel assembly by disconnecting
each quick-disconnect valve.
4. After tires have been isolated, measure and record each
tire's air pressure.
5. After a minimum of 10 minutes, check to see if the air
gauge needles have moved.
NOTE: Leaks can be detected by using soapy water, but com-
mercially available leak detection liquids such as "Gaz-Tec"
work best. Most leaks can be corrected by tightening fittings.
Replace the fittings or air lines only when necessary.
6. Determine if the front, rear, or both air systems have
leaked. If a leak is detected, concentrate on that area and
follow the appropriate troubleshooting chart.
• Geared Hubs, Seals, and Fittings - Chart 1
• Deflate Valve Area - Chart 2
• Under Vehicle Air Leak - Chart 3
7. After checking and repairing leak points, place the selector
switch in the BOTH position.
8. Note the gauge needle positions. Reposition or re-inflate
to align the needles.
9. Wait at least two minutes and check to see if the needles
have moved. If movement is detected, concentrate on
detecting the leak point. Follow Refer to Troubleshooting
Chart 4 – Air Compressor Leak Test in this Section..
NOTE: If tires were hot, air loss may be a result of the tires
cooling down. If this is the case, all tires should lose about the
same amount of air.
10. Check the air pressure in each tire and compare it to the
information taken earlier. Note any air pressure loss and
concentrate on that tire position. Refer to Troubleshooting
Chart 5– Tire and Quick-Disconnect Valve in this
Section..
If no air loss is detected, there may be a small leak which will
require an overnight evaluation.
NOTE: Always complete the entire troubleshooting procedure
to ensure that all potential leak points have been corrected.
Verification
After completing the troubleshooting procedure, verify the sys-
tem by repeating the CTIS Troubleshooting checklist steps.
WARNING: CTIS air system components are subject
to high pressure. Always relieve air pressure before
loosening or removing air system components(s) by dis-
connecting quick-disconnect valve assemblies at each
wheel end. Failure to follow this procedure may result
in serious personal injury.
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