Filter Drier Acid Contamination — Post-Burnout Acid Residue
A field reference for filter drier faults — what causes it, how to confirm it on the unit, how to repair it, and what fails next if you leave it. Written for working HVAC & refrigeration technicians.
How to confirm it on site
- Oil TAN > 0.5 mgKOH/g (normal ≤0.05)
- Oil color: dark brown/black (normal clear)
- Pungent acid smell
- Drier discoloration/heat
- Winding insulation declining
Root causes
- Used standard drier post-burnout (not burn-out type)
- Single cleanup insufficient
- No system flush
- Oil not replaced or partial only
- Burnout not recognized, just compressor swap
If you leave it unrepaired
- Acid residue attacks new compressor winding
- New compressor burns out in 1–6 months
- Oil oxidation → bearing wear
- Refrigerant decomposition
- TXV/SV corrosion
How to fix it
- Use burn-out drier (activated alumina core)
- Replace drier after first 24h + re-test TAN
- If TAN ≥0.05: replace drier 2x or 3x more
- Full oil change + sweep oil change after 24h
- System flush with dedicated solvent
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What causes filter drier acid contamination — post-burnout acid residue?
Used standard drier post-burnout (not burn-out type) Single cleanup insufficient No system flush Oil not replaced or partial only Burnout not recognized, just compressor swap
How do I diagnose filter drier acid contamination — post-burnout acid residue on site?
Oil TAN > 0.5 mgKOH/g (normal ≤0.05) Oil color: dark brown/black (normal clear) Pungent acid smell Drier discoloration/heat Winding insulation declining
How do I fix filter drier acid contamination — post-burnout acid residue?
Use burn-out drier (activated alumina core) Replace drier after first 24h + re-test TAN If TAN ≥0.05: replace drier 2x or 3x more Full oil change + sweep oil change after 24h System flush with dedicated solvent
What happens if filter drier acid contamination — post-burnout acid residue is left unrepaired?
Acid residue attacks new compressor winding New compressor burns out in 1–6 months Oil oxidation → bearing wear Refrigerant decomposition TXV/SV corrosion