HVAC Installation Repair Dispute Letters

Published: December 5, 2025 • Demand Letters, Home
HVAC Installation & Repair Dispute Letters | Contractor Defects & Licensing Issues

HVAC Installation & Repair Dispute Letters

Fight poor installations, sizing errors, and contractor disputes with C-20 licensed contractors

How HVAC Jobs Are Supposed to Be Scoped and Contracted

HVAC work in California requires proper licensing and written contracts. Understanding these requirements is essential to challenging defective or fraudulent work.

C-20 HVAC Contractor License Requirements

In California, HVAC contracting falls under the C-20 Warm-Air Heating, Ventilating and Air-Conditioning classification. This license authorizes:

  • Installing, repairing, and maintaining heating, ventilation, and AC systems
  • Work on furnaces, heat pumps, air conditioners, ductwork, and controls
  • Solar-powered HVAC systems
  • Evaporative cooling systems
License Requirements: To obtain a C-20 license, contractors must:
  • Have at least 4 years of journeyman-level experience
  • Pass technical and law/business exams
  • Maintain workers’ compensation insurance (or exemption)
  • Post a $15,000 contractor bond
Always verify your contractor’s license at cslb.ca.gov before signing a contract.

Written Contract Requirements (B&P Code § 7159)

For HVAC work over $500 (labor + materials), California law requires a written home improvement contract containing:

Required Element Why It Matters
Contractor’s license number Proves contractor is properly licensed; contract is void if unlicensed
Scope of work description Specific systems, models, SEER ratings, tonnage—not vague “install AC”
Start and completion dates Allows you to enforce timely performance; essential for delay claims
Total price and payment schedule Payments tied to specific milestones; no payment for work not done
Right to cancel (3-day cooling off) Allows rescission if signed at home; protects against high-pressure sales
Mechanic’s lien warning Discloses lien risk if contractor doesn’t pay subs
Change order procedure Prevents surprise charges; all changes must be in writing
Red Flags:
  • No written contract: Illegal for jobs over $500; you may rescind and get refund
  • Missing license number: Contractor may be unlicensed; contract is unenforceable by contractor
  • Large down payment: CA law limits down payment to lesser of $1,000 or 10% of total contract (whichever is less)
  • Cash-only, no invoice: Sign of unlicensed or tax-evading contractor; no recourse if work is defective

Service & Repair Contracts vs Full Installations

California distinguishes between:

  • Service and repair contracts: Shorter-form contracts for repairs, tune-ups, diagnostics. Still require license number, pricing, and disclosures but less formal than full home improvement contracts.
  • Home improvement contracts: Full installations or major replacements. Must comply with all B&P § 7159 requirements.

HVAC companies often blur this line, using repair contracts for installations or adding surprise “additional work” charges. Always insist on a compliant written contract before authorizing major work.

Common HVAC Installation and Service Defects

Symptom → Defect → Evidence Matrix

Symptom Likely Defect What to Document for Demand Letter
Some rooms hot, some cold Undersized unit, poor duct design, zoning issues, inadequate returns Temperature logs by room, Manual J load calculation (or lack thereof), second-opinion report, photos of duct layout
High energy bills after new install Low SEER equipment despite promises, improper refrigerant charge, short cycling, oversized unit Utility bills (12 months pre/post), SEER rating on unit vs contract, airflow/static pressure test results, commissioning checklist (if any)
Water leaks, condensation Improper condensate drain, uninsulated refrigerant lines, incorrect pitch, drain pan issues Photos/videos of leaks, water damage photos, repair estimates for ceiling/walls, moisture readings
Excessive noise Undersized ducts (high velocity), loose components, improper mounting, vibration isolation missing Decibel readings, videos of noise, comparison to manufacturer specs, engineer report
Frequent breakdowns Poor installation, refrigerant leaks, electrical issues, undersized components Service call records, invoice history, pattern of repeat failures, technician notes
Trips breakers / electrical issues Undersized wiring, improper electrical connections, code violations Electrician inspection report, photos of electrical panel, permit/inspection records

The Sizing Problem: Manual J Load Calculations

One of the most common and costly HVAC defects is improper sizing. Contractors often “eyeball” sizing (“your old unit was 3 tons, so I’ll install 3 tons”) without performing proper load calculations.

Manual J Load Calculation: Industry-standard method for calculating heating/cooling loads based on:
  • Home square footage, layout, ceiling height
  • Insulation levels (walls, attic, windows)
  • Window orientation and shading
  • Air infiltration and ductwork
  • Climate zone
Why It Matters: Oversized units short-cycle (run briefly, shut off, run again), wasting energy and failing to dehumidify. Undersized units run constantly and never achieve comfort. Both reduce lifespan and increase costs.

How to challenge improper sizing:

  • Request the contractor’s Manual J calculation (they should have performed one)
  • Hire an independent HVAC engineer to perform a proper load calc
  • Show the discrepancy in your demand letter: “Your 4-ton unit was installed without load calculations; proper analysis shows 3 tons was correct, resulting in short-cycling and 40% higher energy bills.”

Ductwork and Airflow Defects

Even a perfectly sized unit will fail if ductwork is poorly designed:

  • Undersized ducts: High velocity, noise, restricted airflow
  • Leaky ducts: 20-30% of conditioned air lost in attics/crawlspaces
  • Poor return air: Inadequate returns starve the system, reduce efficiency
  • Kinked or crushed flex duct: Reduces airflow, strains system

Evidence to gather: Blower door test, duct leakage test (duct blaster), airflow measurements at registers, photos of duct runs.

Manufacturer Warranties vs Contractor Workmanship

HVAC disputes often involve finger-pointing between the equipment manufacturer and the installing contractor. Understanding warranty distinctions is critical.

Warranty Comparison

Warranty Type Who Provides It What It Covers Typical Term Limitations
Manufacturer Parts Warranty Equipment manufacturer (Carrier, Trane, Lennox, etc.) Defects in materials/workmanship of equipment itself (compressor, coils, etc.) 5-10 years parts; often 1 year labor Requires registration, proper installation, regular maintenance; may not cover labor after year 1
Contractor Workmanship Warranty Installing contractor Installation defects (duct leaks, refrigerant charge errors, electrical mistakes, etc.) Typically 1-2 years; some offer 5-10 years Contractor-specific; may exclude “normal wear”
Extended Warranty (optional purchase) Manufacturer or third party Extended parts/labor coverage beyond standard warranty Additional 5-10 years Often expensive; may duplicate existing coverage; read exclusions carefully

When to Go After the Contractor vs the Manufacturer

Sue the contractor if:

  • Installation was defective (sizing, ductwork, refrigerant charge, electrical)
  • System never worked properly from day one
  • Damage was caused by poor workmanship
  • Contractor failed to obtain permits or meet code

File a manufacturer warranty claim if:

  • Equipment component failed (compressor, coil, blower motor) after proper installation
  • System worked fine initially but component failed within warranty period
  • Contractor installed correctly but equipment is defective

Go after BOTH if:

  • It’s unclear whether failure is due to defective equipment or poor installation
  • Contractor blames manufacturer and vice versa (let them sort it out; you just want it fixed)
Demand Letter Strategy: In your demand to the contractor, state: “I am holding you responsible for this defect. If you believe the equipment manufacturer is at fault, you may pursue them, but as the installing contractor you warranted proper installation and system performance. You must make this right.”

Building Code Compliance

HVAC installations must meet California building, mechanical, and electrical codes. Common violations:

  • No permit obtained: Major HVAC work requires permits and inspections
  • Electrical code violations: Undersized wiring, missing disconnects, improper grounding
  • Combustion safety: Improper venting of furnaces, CO risks
  • Refrigerant handling: EPA Section 608 certification required; improper charging is illegal and dangerous

Code violations strengthen your demand letter: they’re objective evidence of defective work and may trigger liability for corrective costs.

Sample HVAC Dispute Demand Letters

Sample 1: Defective Installation – Sizing Error & High Bills

[Your Name] [Your Address] [City, State ZIP] [Email] [Phone] [Date] [Contractor Name / Company] [Address] CSLB License #: [LICENSE NUMBER] RE: Demand for Correction of Defective HVAC Installation Contract Date: [DATE] Property: [YOUR ADDRESS] Total Paid: $[AMOUNT] Dear [Contractor Name]: I demand that you correct the defective HVAC installation you performed at my home and reimburse me for damages resulting from your improper work. BACKGROUND On [DATE], I hired you to replace my HVAC system under a written contract (attached as Exhibit A). The contract called for installation of a [BRAND/MODEL] [TONNAGE]-ton air conditioning system with [SEER] SEER rating, new air handler, and ductwork modifications. Total contract price: $[AMOUNT], paid in full on [DATE]. The work was completed on [DATE]. Since then, the system has performed poorly, resulting in: – Uneven temperatures throughout the home (some rooms 5-10°F warmer than others) – Excessive energy bills (40% higher than before replacement) – Short-cycling (system runs for 5-10 minutes, shuts off, repeats constantly) – Failure to dehumidify during summer months DEFECTIVE INSTALLATION: IMPROPER SIZING I hired an independent HVAC engineer, [ENGINEER NAME], to evaluate the system. His report (Exhibit B) concludes: 1. **You Never Performed a Load Calculation:** You installed a [TONNAGE]-ton unit without performing a Manual J load calculation. A proper load calc shows my home requires only [CORRECT TONNAGE] tons. 2. **Oversized Unit Causes Short-Cycling:** The oversized unit reaches setpoint quickly and shuts off before properly dehumidifying or distributing air evenly. This wastes energy and reduces comfort. 3. **Ductwork Undersized for New Unit:** You installed a higher-CFM unit without modifying undersized ductwork, causing high static pressure, noise, and reduced efficiency. 4. **No Commissioning Performed:** You did not test airflow, refrigerant charge, or static pressure after installation. Industry standards require commissioning to verify proper performance. YOUR CONTRACT AND LEGAL OBLIGATIONS As a C-20 licensed contractor, you are required to perform work in a “good and workmanlike manner” consistent with industry standards. ACCA Manual J load calculations are the industry standard for proper sizing—not guesswork based on the old unit’s tonnage. Your contract states: “Install [BRAND] AC system to manufacturer specifications and applicable codes.” You failed to meet this obligation. Additionally, you failed to obtain a permit for this work. Mechanical permits are required for HVAC replacements in [CITY]. This code violation exposes me to potential issues when I sell the home and demonstrates your substandard practices. DAMAGES As a result of your defective work, I have incurred: 1. **Excess utility costs:** My electric bills averaged $[AMOUNT]/month before replacement and now average $[AMOUNT]/month—an increase of $[AMOUNT]/month. Over [X] months, total excess costs: $[TOTAL EXCESS]. (Exhibit C: Utility bills pre/post installation) 2. **Reduced home value / unmarketable title:** Unpermitted work creates a cloud on title and may require disclosure to buyers, reducing my home’s value. 3. **Cost to correct:** [Engineer] estimates $[AMOUNT] to remove the oversized unit, install a properly sized unit, modify ductwork, and obtain permits/inspections. (Exhibit B: Correction estimate) DEMAND I demand that you, within 30 days: 1. Remove the improperly sized [TONNAGE]-ton unit 2. Install a correctly sized [CORRECT TONNAGE]-ton unit, properly charged and commissioned 3. Modify ductwork as needed to match new unit 4. Obtain all required permits and pass inspections 5. Reimburse my excess utility costs: $[AMOUNT] 6. Provide a written warranty covering workmanship for 2 years from correction date **If you fail to perform corrections, I demand a full refund of $[AMOUNT PAID] plus excess utility costs and cost to hire another contractor.** LEGAL CONSEQUENCES OF NON-COMPLIANCE If you do not respond within 30 days, I will: 1. File a complaint with the CSLB for substandard work, failure to obtain permits, and violations of B&P § 7159 2. Pursue litigation for breach of contract, negligence, and fraud 3. Seek damages including cost of correction, excess utility costs, diminished home value, and attorney’s fees 4. Report unpermitted work to [CITY] building department Your license and bond are at risk. Resolve this now. Please contact me at [PHONE] or [EMAIL] within 30 days. Sincerely, [Your Signature] [Your Printed Name] Enclosures: Exhibit A: Contract Exhibit B: Independent Engineer Report & Correction Estimate Exhibit C: Utility Bills (Pre/Post Installation)

Sample 2: Repair Upcharge Dispute & Unauthorized Work

[Your Name] [Your Address] [City, State ZIP] [Email] [Phone] [Date] [HVAC Company Name] [Address] CSLB License #: [LICENSE#] RE: Dispute Over Unauthorized Charges and Defective Repair Service Date: [DATE] Invoice #: [INVOICE#] Amount in Dispute: $[AMOUNT] Dear [Company Owner / Manager]: I dispute the charges on Invoice #[NUMBER] dated [DATE] and demand a refund of $[AMOUNT] for unauthorized work and defective repair. FACTS On [DATE], I called your company for a “no-cooling” issue with my AC. Your technician, [TECH NAME], arrived and diagnosed a “bad capacitor.” I authorized replacement of the capacitor for the quoted price of $[AMOUNT]. After replacing the capacitor, the technician claimed he found “additional issues”: – Refrigerant leak requiring $[AMOUNT] to repair – Contactor needed replacement: $[AMOUNT] – Coil cleaning: $[AMOUNT] **Total invoice: $[TOTAL], of which I authorized only $[CAPACITOR AMOUNT].** I felt pressured to approve the additional work because the technician said “your system won’t run safely without these repairs.” I reluctantly agreed. The system has continued to malfunction since the repair. The AC still doesn’t cool properly, and I’ve had to call another company to diagnose ongoing issues. WHY I DISPUTE THESE CHARGES 1. **You Did Not Provide a Written Estimate for Additional Work** California law (B&P § 7159.10) requires that if repairs exceed the original estimate by more than $1,000 or 10%, you must provide a written change order signed by me before proceeding. Your technician verbally quoted prices and proceeded without a written change order. This violates the law. 2. **Charges Are Excessive and Inconsistent with Market Rates** I obtained quotes from two other HVAC companies for the same work: – Capacitor replacement: $[MARKET RATE] (you charged $[YOUR CHARGE]) – Refrigerant leak repair: $[MARKET RATE] (you charged $[YOUR CHARGE]) – Contactor: $[MARKET RATE] (you charged $[YOUR CHARGE]) Your charges are 200-300% above market rates. This is unconscionable and suggests predatory pricing. 3. **The Repair Was Ineffective** Your technician claimed the repairs would fix the cooling issue. They did not. I hired [INDEPENDENT COMPANY] to evaluate the system. Their report (Exhibit A) states: “The capacitor, contactor, and coil were replaced, but the underlying issue—a failed compressor—was not addressed. The capacitor and contactor replacements were unnecessary; the compressor failure was the root cause.” You performed unnecessary repairs and failed to diagnose the actual problem. This is either incompetence or fraud. DEMAND FOR REFUND I demand a refund of $[AMOUNT], representing: – Overcharges compared to market rates: $[AMOUNT] – Cost of unnecessary repairs (capacitor/contactor were fine per independent tech): $[AMOUNT] – Cost to hire independent technician to diagnose your botched repair: $[AMOUNT] I will pay only the reasonable cost of the initial service call and capacitor replacement: $[AMOUNT]. I have already paid $[TOTAL PAID], so you owe me a refund of $[REFUND AMOUNT]. If you do not issue a refund within 21 days, I will: – File a complaint with the CSLB for deceptive practices and overcharging – Dispute the charge with my credit card company – Pursue litigation for fraud, unfair business practices (B&P § 17200), and breach of contract – Post detailed reviews on Yelp, Google, and BBB documenting your practices – Report to local consumer protection agencies Your business thrives on trust. Do the right thing and refund the excess charges. Please contact me at [PHONE] or [EMAIL] within 21 days. Sincerely, [Your Signature] [Your Printed Name] Enclosures: Exhibit A: Independent Technician Report Exhibit B: Market Rate Quotes from Competitors Exhibit C: Invoice from Independent Repair (correcting your work)

Evidence Checklist for HVAC Disputes

What to Gather Before Sending Your Demand

Essential Documents:
  • Contract: Original written agreement with scope, price, payment schedule
  • Invoices and receipts: All payments made, including deposits and final payment
  • Permits and inspections: Copies of building permits (or proof none were obtained); inspection reports if available
  • Manufacturer specs: Specifications for equipment installed (model numbers, SEER ratings, tonnage)
  • Utility bills: 12 months pre-installation and post-installation to show increased costs
  • Service records: All service calls, repairs, warranty claims since installation
  • Photos and videos: Installation in progress, completed work, defects (leaks, duct issues, electrical), temperature differentials
  • Independent assessments: Second-opinion reports from licensed HVAC engineers or contractors

Technical Evidence to Strengthen Your Case

Type of Evidence What It Proves How to Obtain
Manual J Load Calculation Correct system size for your home; shows contractor’s sizing was wrong Hire HVAC engineer or use online Manual J software; compare to contractor’s calc (or lack thereof)
Airflow measurements CFM at registers, static pressure in ducts; identifies undersized ducts or restrictions Independent technician with flow hood and manometer
Refrigerant charge test Superheat/subcooling measurements show if system is properly charged Licensed technician with gauges; compare to manufacturer specs
Duct leakage test Percentage of air lost through leaks; industry standard is <10% Duct blaster test by energy auditor or HVAC pro
Energy bills comparison Cost increase after installation; quantifies damages 12 months before/after; normalize for weather using degree days
Temperature logs Room-by-room temps show uneven distribution Digital thermometers; log temps at same time daily for 1 week

Contractor License Verification

Before sending your demand, verify the contractor’s license status at cslb.ca.gov. Check:

  • License number and classification: Should be C-20
  • License status: Active, expired, suspended, revoked?
  • Complaints and disciplinary actions: History of similar issues?
  • Bond and insurance: Current workers’ comp insurance?
If Contractor Is Unlicensed: You have powerful leverage. Under B&P § 7031, an unlicensed contractor cannot sue to enforce a contract or collect payment. You may be entitled to a full refund of all payments made, plus damages. Mention this in your demand letter.

Attorney Services for HVAC Contractor Disputes

HVAC disputes often involve significant amounts ($5,000-$50,000+) and technical complexity. I help homeowners hold contractors accountable for defective installations and unfair practices.

Why You Need an Attorney

  • Technical complexity: HVAC cases require expert witnesses (engineers, energy auditors) to prove defects
  • Code and licensing issues: Violations of B&P § 7159, CSLB regulations, building codes strengthen your case
  • Contractor bond claims: I can pursue claims against the contractor’s $15,000 bond if needed
  • Litigation leverage: Contractors take attorney-represented demands seriously; many settle to avoid CSLB complaints and litigation
  • Recovering attorney fees: California allows fee recovery in contractor disputes under Civil Code § 1717 and B&P § 7031

My Approach

  1. Case evaluation: Review contract, invoices, and evidence; identify violations and calculate damages
  2. Expert retention: I work with HVAC engineers, energy auditors, and code compliance specialists
  3. Pre-litigation demand: Detailed letter with technical evidence, code violations, and legal analysis
  4. CSLB complaint: File or assist with Contractors State License Board complaint for leverage
  5. Negotiation and settlement: Most cases settle when contractor faces expert reports and regulatory pressure
  6. Litigation: If needed, I file suit for breach of contract, fraud, and violations of B&P § 7159

Fee Structure

  • Contingency: Percentage of recovery (typically 33-40%); no fee if no recovery
  • Hourly: For cases where liability is clear and settlement likely
  • Hybrid: Reduced hourly plus success fee

Many contractor cases qualify for attorney fee shifting, making representation cost-effective.

Submit Your Case for Review

If you’re dealing with a defective HVAC installation, overcharges, or an unresponsive contractor, I can help. Send me your contract, invoices, and photos for a case review.

Serving California homeowners. Contingency fees available. I hold contractors accountable.

Additional Resources