Bulletin No.: PIT6290A
Published date: 02/12/2025

Preliminary Information
PIT6290A Diagnostic Aid for No/Poor Heat With Possible P0530
and/or P0534
Models
Brand:

Model: Model Years:

Chevrolet Blazer EV 2024 - 2025

VIN:
Engine: Transmissions:
from to
All
All All
All

Involved Region or
Country

North America

Condition

A whistle noise may be present when the system switches from
cabin heating to full cooling (AC on)
Code P0530 and/or P0534 may be set.
While driving the heat may begin to blow cold and blower speed
drop intermittently.

Cause

Possible faulty AC condenser check valve or improperly formed
AC line at mating surface of condenser check valve- air
conditioning condenser hose.

Correction:
If P0530 and/or P0534 is set but is not accompanied by a whistle noise or an intermittent
loss of heat concern please refer to the following PI's before following the direction in this
PI.
PIT6257P0534 Service High voltage System Message
PIT6112A P0534 Service High Voltage Diagnostic Tips
PIT6183 AC Does Not Work-Service High Voltage Message
If the concern is not addressed with any of the above PI's or there is a complaint of a
whistling noise or heat is dropping out perform the steps below.
Set the HVAC system to auto high (Max Heat).
Run the system for 5 to 10 minutes.
Using GDS2 monitor refrigerant temperature sensors 6 and 8. There should be a
minimum of 50 deg. F difference between them.
Monitor Air Conditioning Condenser Refrigerant Flow Valve-External Command for a
reading of zero.
If the variance between sensors 6 and 8 is more than 50 deg. or the flow valve command is
more than zero follow SI diagnostics for the code or symptoms experienced.
If the variance is 50 deg or less and the flow valve command is zero verify the reading by
measuring the temperature above and below the AC condenser check valve- AC condenser
hose with an infrared temperature gun. #18 in diagram below.

Location of valve on vehicle.

If the variance is less than 50 deg. inspect to make sure the arrow on the check valve is
pointing up in the direction of refrigerant flow and then remove and inspect the valve.
Inspect the pintle and spring to ensure they are not loose or missing from the check valve.
When the valve is shaken it should not rattle.
Inspect the seals for being pinched or cut.
Picture of seal misplaced and damaged in valve.

If any damage is noted to the check valve it should be replaced.
If no damage is noted in the valve or before replacing the valve if it is damaged, inspect
the opening in the pipe where the lower end of the check valve connects.
The opening should be no less than 6mm in diameter and should be centered in the pipe.
Test the size of the opening by attempting to insert a 6mm drill bit. See photo below of an
improperly formed line.

If the opening is undersize or off center it will need to be enlarged and centered using the
procedure below.

If the line is severely damaged so that it cannot be modified it will need to be replaced.
(see example below)

AC line Repair Procedure:
Remove the pipe from the vehicle.
Insert a piece of a paper shop towel into the pipe to catch any shavings that may drop in.
Using a clean, no grease or dirt, 6mm drill bit and applying hand pressure only, gently
ream the hole to enlarge the opening to 6 mm and center it. (if the hole is slightly larger
than 6 mm when done this is acceptable).
After the hole is modified, use shop air on the opposite end of the line to remove the paper
towel and push out any debris.
Thoroughly blow the pipe out from both ends to remove any particles that may have fallen
into the pipe.
Reinstall the pipe, with a new valve if necessary, recharge system and retest temperatures
using GDS2.

Test drive the vehicle to confirm the repair.
Version History
Version22
Modified

11/22/2024 - Created on.
02/12/2025- Removed whistle noise from title.

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