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When your AC hums but the fan won’t spin, or your heat pump just clicks, the 40/5 capacitor is usually the quiet culprit. This one part starts both the compressor and the fan motor, and swapping it yourself is a 15-minute job that keeps you out of the heat and your wallet intact.
I’m Min — the founder and writer behind Gadgets Feed. This guide is built by comparing the manufacturers’ published specifications and the patterns across verified customer reviews, so you get each pick’s real strengths and trade-offs instead of marketing spin.
You need the right replacement to avoid a repeat failure, so here is the breakdown of the best 40/5 capacitor options on the market today.
Our Picks at a Glance
How To Choose The Best 40/5 Capacitor
Choosing a 40/5 capacitor is mostly about matching numbers, but a few details separate a perfect fit from a frustrating mismatch. A “40/5” part is a dual-run capacitor, meaning it holds two jobs at once: 40 microfarads for the compressor and 5 microfarads for the fan motor.
Match the Microfarad (MFD) Rating Exactly
The most important rule is that the capacitance value must match your old part’s rating. Swapping a 40/5 for a 45/5 can overwork the motor, while a lower value might prevent it from starting at all. Look for the printed numbers on the side of your old capacitor and order the identical MFD rating.
Check the Voltage Rating
You can usually go up in voltage, but never down. If your system calls for a 370-volt part, a 440-volt replacement is safe because it has a higher tolerance for electrical surges. The reverse is dangerous, so always pick a part rated at least as high as the original.
Look for the Safety and Build Standards
Quality capacitors carry UL listings and meet industry standards like EIA-456-A, which signal they have passed safety and performance tests. Materials matter too — metalized polypropylene film with a sealed aluminum case handles heat better and resists the oil leaks that cause early failure.
Quick Comparison
| Model | Best For | Capacitance | Max Voltage | Item Dimensions W x H | Amazon |
|---|---|---|---|---|---|
| Genteq C3405R★ Best Overall | OEM-grade match | 40 microfarad | 370 volts | 2″ x 3.88″ | Amazon |
| TEMCo CBB65Premium Pick | High-heat tolerance | 40 microfarad | 440 volts AC | 1.96″ x 5.36″ | Amazon |
| Titan TRCFD405 | Keeping a spare on hand | 40 microfarad | 370 volts AC | — | Amazon |
| BOJACK CBB65 | Quick heat pump fixes | 45 microfarad | 370 volts | 1.97″ x 3.55″ | Amazon |
| The HVAC Genius 40/5 | Broad Carrier compatibility | 40 microfarad | 440 volts | 2.07″ x 4.8″ | Amazon |
| Genteq 97F9838/C4405R | Replacing a 370V with more headroom | 40 microfarad | 440 volts | 2.13″ x 4.75″ | Amazon |
| AmRad USA2235 | Made-in-USA longevity | 40 microfarad | 440 volts | — | Amazon |
In‑Depth Reviews
1. Genteq C3405R 97F9849 Capacitor Motor Run
Our pick — over 4.5★ from 900+ verified ratings; the strongest balance of quality and price.
The OEM-grade round that HVAC pros reach for first when they need an exact match.
If you want the same part the original equipment manufacturers spec, this is it. The Genteq C3405R is a 40 microfarad dual-run capacitor rated for 370 volts, and its claim to fame is a 60,000 hour run life, which translates to many summers of steady cooling. Buyers report it is “simple to install, works as designed,” and that it is an exact, identical fit for the original part their AC shipped with.
It also carries a 6% capacitance tolerance, meaning the measured value stays very close to the 40 microfarad rating, which keeps your compressor and fan starting reliably. The round body is 2″W x 3.88″H, so it slips into the same mounting bracket slot as most factory parts without needing new holes or adapters. The copper material and snap-in mount make this a true drop-in swap for a homeowner.
There is one quirk to know: Genteq was acquired by Capcom, so the box and label may say “CapCom” even though the part is identical. A few buyers noted this caused brief confusion, but the consensus is clear that it is the same reliable component. The crowd favorite among serious DIYers, this part holds a 4.7-star score from over 900 owners who repeatedly call it a glove-like fit and great value.
Why Owners Trust It
- Exact OEM match for most factory condensers
- 6% capacitance tolerance keeps values accurate
- Copper build rated for 60,000 hours
Watch Out For
- Label may read “CapCom” instead of Genteq, causing brief confusion
- Longevity is untested by some early buyers
Grab this for: a factory-grade replacement that matches the original part’s fit and rating without adaptation.
Consider the alternative: if you need a higher 440-volt safety margin, the TEMCo below offers more surge headroom.
2. TEMCo 40+5 uF Dual Run Capacitor CBB65
A heavy-duty aluminum round rated for 440 volts that shrugs off brutal summer heat.
Hot climates are where this one shines. The TEMCo CBB65 is a 40+5 uF dual-run capacitor rated for 370 or 440 VAC, giving you a higher surge ceiling than a 370V-only part, and it operates from -40°C to +85°C. That wide temperature range means it keeps working even when your exterior condenser is baking in direct sun, which is exactly when capacitors tend to fail.
The build is serious too: a heavy-duty aluminum casing with a steel cap, stuffed with metallized polypropylene film and epoxidized soybean oil, and it is PCB-free with a 10,000 AFC short-circuit rating. It measures 1.96″W x 5.36″H, which is noticeably taller than the Genteq C3405R’s 3.88″ height — so check your cabinet space before buying. The 1/4″ quick-disconnect terminals make the swap fast, and the 5-year warranty backs the long-term bet.
If your AC fan stops, this capacitor can get it running again in under 5 minutes, as one reviewer noted. A Rheem owner also avoided a costly service call by swapping this part themselves. Durability feedback is mixed: one owner saw a failure within a year, but the warranty replacement was quick. The 440-volt rating (compared to a standard 370V) gives extra surge protection, making it a smart pick for hotter regions.
Heat-proof build: the 440-volt rating and -40°F to +185°F operating range make it a rugged choice for sun-baked condensers.
Honest trade-off: durability gets mixed owner feedback, so keep your receipt for the 5-year warranty.
3. Titan TRCFD405 Dual Rated Motor Run Capacitor
An American-made 40/5 round that owners keep on the shelf for when the AC inevitably dies.
There is a school of thought among experienced owners: buy the capacitor before you need it. The Titan TRCFD405 is built for exactly that, with a 60,000 hour reliability rating and a dual 440/370 volt design that fits either system. It is a 40+5 MFD round made with heat-tolerant metalized polypropylene film, and it meets EIA-456A, IEC 60252-1:2001, and UL 810 standards.
At 6.24 ounces, it feels solid in hand, and the through-hole mount pairs with the clearly marked posts that owners say make installation a breeze. One buyer replaced a 20-year-old original and found it “installs as easily as the old one,” while another called it a “quality capacitor at a reasonable price” that has run for years across multiple AC units. Several people specifically praise it as a spare, noting they never worry about a blown capacitor on a 10-year-old system.
The honest caveat is that durability gets mixed feedback, with some owners reporting a failure inside 9 months of heavy use. That said, the value story is strong — One owner reported saving the cost of a professional HVAC visit. — and the American-made quality is a consistent theme across the positive reviews. This is the one to grab if you want a dependable standby.
Built for standby duty: the 60,000-hour rating and dual-voltage design make it a confident spare to stash in the garage.
Reality check: a small share of owners saw failure around the 9-month mark, so buy from a seller with easy returns.
4. BOJACK 40+5uF 40/5MFD ±6% 370V CBB65 Dual Run Capacitor
The budget-friendly round with the clearest terminal labels for a stress-free first swap.
If this is your first capacitor replacement, the BOJACK takes the guesswork out. The three terminals on top are clearly labeled “Herm”/”H” for the compressor, “Fan”/”F” for the fan, and “C” for the common line, so you can match the wires without second-guessing. It is a 40+5uF dual-run capacitor with a ±6% tolerance rated for 370 volts, operating from -40°C to +70°C.
It measures 1.97″W x 3.55″H, making it one of the more compact options here — short enough to fit tight condenser cabinets where the taller TEMCo won’t. The 10,000 AFC safety rating means it can handle a short circuit without rupturing. A buyer with a Rheem unit tested it with a multimeter right from the start, confirmed it was good, and had their HVAC “jumped right up with no issue” in about 15 minutes.
The value angle is strong, Owners noted it saved hundreds on a service call.., and several mentioning it works particularly well for heat pumps. Durability gets mixed reports — some owners get almost exactly 3 years, others less — but the price per year of service is hard to argue with. This is the pick for a quick, confident DIY repair without overspending.
First-Timer Friendly
- Herm, Fan, and C terminals printed clearly on top
- Compact 3.55″ height fits tight cabinets
- Cheap enough to keep one spare on hand
Keep In Mind
- Mixed durability reports, some around the 3-year mark
- 370V rating means no surge headroom above spec
Reach for this if: you want an inexpensive, clearly labeled part for a first-time DIY heat pump or AC fix.
Look elsewhere if: you demand a higher 440V safety margin for scorching climates.
5. The HVAC Genius 40/5 uF Dual Run Start Round Capacitor
A premium aluminum round with the longest compatibility list for Carrier and Lennox systems.
Some capacitors are built for one brand; this one is built for a dozen. The HVAC Genius is a 40/5 uF dual-run capacitor rated for 440 volts, and it explicitly replaces a huge list of part numbers including 97F9838, RC0108, C3405R, and TRCFD405. That makes it a safe bet if you are not 100% sure which OEM part your system uses, as it is “compatible with most Carrier AC Capacitor” setups and other cylindrical HVAC parts.
It runs at 50/60 Hz with an operating temperature range of -40°C to +85°C, and it is safety rated at 10,000 AFC. The aluminum body measures 2.07″W x 4.8″H, and it complies with EIA-456-A and IEC 60252-1:2001 standards with UL and CUL listings. Owners describe AC units “back up and running in 10 minutes,” and one noted the part went in with no issues after the old one read low.
The 440-volt rating (compared to a 370V part) means it can handle voltage spikes better, protecting your AC from surges. The retail packaging adds confidence. One caution: a single buyer found theirs was the wrong size/wattage for their unit, so double-check your old part’s numbers before ordering. Overall, buyers agree this is a reliable, fast fix that saves a service call…
Compatibility king: the broad replacement list makes it the right pick when you’re unsure of the exact OEM part number.
Double-check first: confirm your old capacitor’s MFD and physical size, as one owner received the wrong fit.
6. Genteq 97F9838/C4405R Round Capacitor
The 440-volt Genteq that gives you a higher ceiling without changing the fit.
There is a well-known rule in HVAC: you can replace a 370V capacitor with a 440V one, but never the other way around. The Genteq 97F9838/C4405R is the 440-volt version of the brand’s classic 40/5, giving you extra headroom against power surges while keeping the exact same 40 microfarad capacitance. It measures 2.13″W x 4.75″H, so it is only slightly wider than the C3405R and typically fits the same bracket.
Owners love the value: Owners reported DIY savings and avoiding technician fees.. Hands-on reports are consistent: an AC that stopped cooling was fixed in about 10–15 minutes. One buyer measured the new part at 40.6+5.4 µF on a multimeter, nearly identical to spec, while the old unit was dead at 17nF. “If your condenser calls for this, get it” sums up the sentiment.
This is a from a trusted OEM brand, though the ceramic material note in the listing is worth a second glance. The durability feedback is mixed — some owners mention over a year of solid service, others hit issues sooner — but the fit, cooling performance, and exact-replacement value are consistently praised. This is the go-to if you want the brand name with more voltage margin.
Smart upgrade path: moving from a 370V to this 440V part adds surge protection with the same MFD and a near-identical footprint.
Not a guarantee: durability gets mixed reviews, so buy where the return policy is easy.
7. AmRad USA2235 Round Dual Universal Capacitor
The American-made 40/5 that owners say outlasts the imports and earns its higher price.
If you want to buy this part once and stop thinking about it, the AmRad is the one. It is a 40 + 5 uF/Mfd round dual capacitor that runs on either 370 or 440 VAC, and it is proudly made in the U.S.A. — a detail that comes up again and again in owner feedback, often with a clear preference for AmRad over parts assembled in Mexico. It weighs 8 ounces, feeling notably sturdier in hand than lighter budget rounds.
Build quality stands out: owners describe years of reliable service, with one emphatic note: “don’t cheap out and buy inferior ones, this product lasts.” It saved one buyer a service call., and another had their unit running in less than 5 minutes after a simple swap. The optional CPT terminal (a connection for certain systems) is there if you need it, but you can ignore it if not.
The trade-off is the price, which sits at the premium end of the 40/5 category. For most homeowners, the budget BOJACK or mid-range Genteq will do the job fine. But for those who want a domestic-made part with a reputation for durability, the AmRad is the clear choice — often described as the best quality capacitor you can buy for this application.
Built to Last
- Made in the USA with a durable polypropylene build
- Dual 370/440V rating for broad compatibility
- Customers note years of reliable service
Premium Trade-Off
- Costs more than budget 40/5 alternatives
- Optional CPT terminal adds slight complexity
Ideal for: buyers who want a premium, American-made part and are willing to pay more for proven durability.
skip it if: you are on a tight budget and just need a one-season quick fix.
Understanding the Specs
Microfarad Rating (MFD/uF)
The microfarad rating tells you how much electrical charge the capacitor can store. A 40/5 label means 40 microfarads for the compressor and 5 microfarads for the fan motor. Swapping in a different value can cause the motor to overheat or fail to start, so you must match this number to your old part exactly.
Voltage Rating (VAC)
The voltage rating indicates the maximum electrical pressure the capacitor can safely handle. A 440-volt part can replace a 370-volt one because it has a higher safety margin, but the reverse is risky. Check your system’s label — if it calls for 370V, a 440V capacitor is a safe upgrade.
FAQ
How do I know if a 40/5 capacitor fits my air conditioner?
Is a 440V capacitor better than a 370V one?
Can I replace a 370V capacitor with a 440V one?
How long does a 40/5 capacitor typically last?
What do the Herm, Fan, and C terminals mean?
Is it safe to replace a capacitor myself?
What happens if I use the wrong MFD value?
What is the difference between a start capacitor and a run capacitor?
Final Thoughts: The Verdict
For most buyers, the 40/5 capacitor winner is the Genteq C3405R because it combines an OEM-grade fit with a 60,000-hour run life and an unbeatable owner consensus. If you want a higher 440-volt safety margin for a hot climate, grab the TEMCo CBB65. And for a budget-friendly first-time fix with the clearest labels, the BOJACK is the one to reach for.
How We Picked
We do not accept paid placement. Every pick is matched to a real buyer and a real use-case; we do not hands-on test units.
Sources & Methodology
Specifications: manufacturer listings and product documentation. Review insights: verified customer reviews, as of September 2026. Pricing: not shown on this page (it changes often); check the current price via the retailer link.
As an Amazon Associate, Gadgets Feed earns from qualifying purchases. This does not affect which products we feature.