How do I know if my contactor is bad?

Pitted or burned contacts, a buzzing sound when the AC tries to start, or the contactor sticking closed (AC runs constantly, never cycles off). Pull the front cover and look at the contacts — if they're black or pitted, replace it.

Can I use a higher amp rating?

Yes. Going up in amps is fine (40A replacing a 30A is safe). Coil voltage MUST match exactly — 24V coil only goes in 24V circuits.

2-pole vs 3-pole — which do I need?

Count the thick wires hitting the line side (top). 2 fat wires = 2-pole (residential split-system). 3 fat wires = 3-pole (3-phase commercial). Most residential is 2-pole.

How long does a contactor last?

5-10 years typical. Insects, dust, and short-cycling shorten the life. If you find ants or wasps nesting in your condenser, that often kills contactors fast.

Low Stock

Universal

2P40A120V – CONTACTOR (C240B)

Name: 2P40A120V - CONTACTOR (C240B)
Brand: Universal
SKU: 2P40A120V
Price: 36.52 USD
Availability: InStoreOnly

SKU 2P40A120V·Replaces C240B, CONTACTOR

$36.52

In-store price · paid at counter

Low Stock at our Dallas counter

Tested before you leave. Free at the counter.

In-Store Only — We Don’t Ship

Every part is sold in person at our Dallas counter. No shipping, no online orders. Solo venta en tienda — no hacemos envíos.

Visit our Dallas counter to purchase

10226 Plano Rd, Suite 104 · Dallas TX 75238

Call (214) 340-9421 Get directions

Open now · Closes 7pm·Mon–Fri 10am–7pm · Sat 10am–3pm

Free part testingBench-tested at the counter

27,000+ in stockToday, on the shelf

4.9 · 546 reviewson Google

Since 199828 years on Plano Rd

Pro tip

When you swap a contactor, also pull the capacitor and bring both in — pitted contactor contacts almost always mean the cap was weak and the compressor was straining to start. We'll test the cap free, and if it's marginal you'll save yourself a second trip.

Free Part Testing

27,000+ In Stock

4.9 Stars · 546+ Reviews

Since 1998

🏪 In-Store Pickup Only — We do not offer shipping or online ordering. Visit our Dallas location to purchase.

In Stock

Visit our Dallas store to purchase

Call (214) 340-9421 Get Directions

In Stock — Pick Up at Our Dallas Store

10226 Plano Rd, Suite 104, Dallas TX 75238

Questions? Call or text (214) 340-9421

Mon–Fri 10 am – 7 pm | Sat 10 am – 3 pm

Symptoms of failure

AC will not start and you hear a buzz or chatter at the contactor
Contacts look pitted, blackened, or welded together
Unit runs constantly and will not shut off when the thermostat is satisfied
Loud chattering from the outdoor unit that comes and goes
Ants or debris packed around the contacts
Thermostat calls for cool and nothing happens outside

Seeing these does not always mean this part is the culprit. Bring the old one in and we will meter it at the counter, free, before you buy.

If your AC clicks but doesn’t start, or the outdoor unit won’t turn on at all, the contactor is the first thing to check. This two-pole 40A contactor uses a 120V coil — less common than 24V in residential but used in certain commercial and specialty setups where the control circuit runs on line voltage.

Replaces: C240B, 2P40A120V

Fits: Commercial and specialty AC systems requiring a 2-pole 40A contactor with 120V coil

Need help? See our AC Clicking But Not Starting Guide.

In stock at Open To Public HVAC Parts in Dallas. We test parts at the counter before you buy. Call or text (214) 340-9421.

Specs

Poles2
Amps40 RLA (full load)
Coil Voltage120V AC
TerminalsScrew + push-on quick-connect
Operating Temp-40°F to 158°F
UL ListedYes

Installing it yourself

Difficulty 2/5Typical time 20-30 minutes

Kill power at the disconnect and confirm 0V.
Photograph the wiring first. Line, load and the 24V coil all land in specific places.
Move one wire at a time from old to new so you cannot cross them.
Match pole count, coil voltage (usually 24V) and FLA rating. FLA is the number that matches a compressor, not the resistive rating.
A 2-pole is a safe upgrade over a 1-pole with shunt. Going the other way is not.
Mount, land the wires, restore power.
If it chatters again with a new contactor, the problem is low control voltage, not the contactor.

Power off at the disconnect first, every time. Not sure partway through? Bring it to the counter and we will walk it with you.

$36.52

Low Stock · Dallas counter

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