AC Not Cooling? What an HVAC Diagnostic Costs
Typical market range as of May 2026 · regionalized for northern Illinois
Most homeowners
$125
When your AC is running but not cooling, the first thing you pay for is a diagnostic — the tech's time and tools to find out what's actually wrong before quoting a fix. A standard residential diagnostic visit typically runs $75–$200, with $125 being common in the Chicago suburbs. Many techs credit that fee toward the repair if you approve the work same-day, so always ask whether it's applied or charged on top.
Pricing this job, not hiring for it? See what the work is worth →What drives the price
After-hours & weekends
Nights, weekends, and holidays commonly run 1.5–2× the standard fee.
Peak season
First heat wave of summer is the busiest window — fees and wait times both climb.
Credited vs. stacked
Some techs waive or credit the diagnostic if you book the repair; others charge both. Confirm up front.
Refrigerant leak search
A simple no-cool check is quick; a dye or electronic leak search adds time and cost.
In our market — McHenry County & northern Illinois
Across McHenry County and the northwest Chicago suburbs, $99–$149 is the typical weekday diagnostic. The first 90°F stretch of the season spikes demand hard — booking before the heat hits usually means a lower fee and a same-week slot.
Walk in informed
A diagnostic should produce a clear written finding — what's wrong and what the repair costs — before any work starts. Be wary of a tech who skips the diagnosis and jumps straight to 'you need a whole new system.'
Fair Price Guide is iHVAC's market research for informational purposes and is strictly advisory. Actual prices are set by the independent technician. iHVAC is not a party to any transaction and assumes no liability, operating with zero middleman billing or liability.
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For the tech
What this work is actually worth
Undercharging is the chronic problem for independent and side-job techs — you quote the part plus a little, forget what it really costs to show up, and train customers to expect cheap. The ranges above aren't a ceiling. Here's how to think about pricing this job so you're not working for free.
Why it's worth it
Your diagnostic time is the product — the years of pattern recognition that let you find a no-cool fault fast. Charging a real diagnostic fee isn't nickel-and-diming; it's pricing the expertise that saves the homeowner from a wrong guess.
Don't undercut yourself
Waiving the diagnostic 'to win the job' trains customers to expect free expertise and eats your windshield time. If you credit it toward the repair, say so — don't just give it away.
Build these into every price — not just the part:
Drive + windshield time. The hour each way isn't free. If you're not billing for getting there, you're working below your hourly.
Truck, tools, fuel. Your van, gauges, recovery machine — what they cost to own and run is overhead on every single call.
License, insurance, bond. Carrying real coverage is what separates you from the unlicensed guy. It has to be priced in, not eaten.
Callback & warranty risk. Some jobs come back. A price with zero margin for a return trip loses money on the ones that do.
Taxes & self-employment. As a 1099 independent you owe self-employment tax and your own withholding. The number you charge isn't the number you keep.
Your expertise isn't free. Knowing exactly what's wrong in five minutes is the product. An unskilled-labor rate undersells the one thing customers can't get elsewhere.
Help build the real number
The most accurate guide isn't built from national averages — it's built from what techs in your area actually charged. Contribute what you charged for this job and it feeds the local range here. It's opt-in, fully anonymized, and only ever shown as an aggregate once enough techs have contributed — never your individual price, never a price iHVAC sets, never a floor anyone has to hold. Just real market information, so the whole trade prices its work fairly.
Contribute what you chargedCommon questions
Is the diagnostic fee credited toward the repair?
Often, but not always. Many techs apply it to the repair if you approve the work the same day. Ask before they start so there are no surprises on the invoice.
Why won't my AC cool even though it's running?
Common causes are a tripped or weak capacitor, low refrigerant from a leak, a frozen evaporator coil, a failed contactor, or a dirty condenser. The diagnostic exists to tell you which one — and the repair costs vary a lot between them.
Should I pay a diagnostic fee at all?
Yes — a real diagnosis protects you. The fee buys an honest finding so you're not guessing or paying for parts you don't need.
Related costs
How we research these numbers
This range is synthesized from published 2025–2026 US HVAC cost data and HVAC field knowledge, then regionalized toward northern Illinois. It's market reference — not a quote, and not a price iHVAC sets. As real techs complete jobs on iHVAC, these ranges will be backed by the actual local prices homeowners pay — the most accurate source there is.
References triangulated for this guide: