| Subject: | Production Changes to A/C System Components, Revisions
to Reduce Possible Passenger Compartment Hiss Noise and New Charging Guidelines |
| Models: | 1999 Chevrolet Corvette |
This bulletin is being revised to clarify and add additional
A/C system changes. Please discard Corporate Bulletin Number 99-01-39-006
(01 -- HVAC).
This information is intended to aid the technician by outlining
the 1999 changes to the A/C system and the normal sounds associated with it.
On April 12, 1999, several production changes were instituted
to reduce a possible hiss type noise. Previous to this production date, a
hissing sound may have been audible inside the passenger compartment while
the A/C compressor was in operation. A hissing sound may be created when the
high pressure R134a liquid refrigerant changes into a gas as it passes through
the expansion tube. No attempt should be made to alter the previous system,
as it is functioning correctly.
The April 12, 1999 revisions to the system
are as follows:
| • | The expansion tube (or orifice) is relocated to the front refrigerant
line, closer to the condenser. |
| • | The expansion tube goes from a 1.83 mm (.072 in)
diameter to a 1.57 mm (.062 in) diameter. |
| • | The revised front and rear refrigerant lines can only be used
as a pair. The new design and old design cannot be mixed. |
Charging Guidelines
| • | Vehicles built after April 12, 1999 equipped with
the revised refrigerant lines, were charged from the factory with 0.68 kg
(1.50 lbs) of R134a refrigerant. Near the end of the 1999 production,
a running change was made to increase the refrigerant charge to 0.794 kg
(1.75 lbs). The factory charge amount can be verified by checking the
A/C system label affixed to the front passenger side wheelhouse. |
| • | For vehicles factory charged with 0.68 kg (1.50 lbs)
of refrigerant, the charge may be increased to 0.794 kg (1.75 lbs)
only if the system must be evacuated for repair purposes. |
| | Important: Do not increase the charge unless repairs to the system or other components
necessitate evacuation of the system.
|
| • | If a vehicle's reported customer concern is insufficient cooling,
the system charge may be increased to 0.794 kg (1.75 lbs).
All A/C system diagnostics in the Service Manual should be followed in conjunction
with the refrigerant increase. |
| • | Increasing the system charge should not be considered a "fix"
for insufficient cooling, as it will have only a minimal affect on system
performance. If the system charge is increased to 0.794 kg (1.75 lbs),
the underhood charge label must be replaced with P/N 10432250. |
Part Number
| Description
|
10432250
| Label, A/C Charge
|
Parts are currently available from GMSPO.
