A/C Request A Circuit High
The P2521 code means the vehicle's onboard diagnostic system has detected: A/C Request A Circuit High. This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $80 - $400 (parts and labor)
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Common Symptoms
- A/C compressor runs continuously
- A/C cannot be turned off
- Check engine light on
- Excessive fuel consumption from constant A/C load
Probable Causes (Ranked by Likelihood)
- Short to voltage in A/C request circuit Very High
- A/C relay stuck in engaged position High
- Climate control module sending constant request Moderate
- Wiring harness damage near A/C components Low
Step-by-Step Diagnostic Procedure
-
Check A/C request signal voltage at ECM for constant high
-
Test A/C relay for stuck contacts
-
Inspect A/C request circuit wiring for short to power
-
Scan climate control module for faults
Frequently Asked Questions
Why does my A/C compressor run even when turned off?
P2521 indicates the request signal is stuck high, making the ECM think the A/C is always requested. A shorted wire or stuck relay is the usual cause.
Will constant A/C operation damage anything?
It increases fuel consumption and puts unnecessary load on the engine and compressor. Prolonged operation without cycling can also freeze the evaporator.
Can I pull the A/C relay to stop the compressor?
Yes, removing the A/C compressor relay is a temporary workaround until repairs are made. This will disable A/C completely.
Sources
This page is built from documented references. Verify against your own service info before repair work.
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