Starting capacitors in place on an air conditioning compressor (C) InspectAPedia.comMotor Capacitor Wiring FAQs
Wiring Q&A for HVAC & Other Electric Motor Start / Run Capacitors

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Q&A on how to hook up an electric motor start or run capacitor:

FAQs on how to wire a motor start/run capacitor or dual run capacitor includes wiring connections & wire colour codes.

This article series gives electric motor start-run capacitor installation & wiring instructions for electric motor capacitors designed to start & run an electric motor such as an AC compressor, heat pump compressor or a fan motor.

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Q&A on How to Connect the Wire on a Start / Run Motor Capacitor

Motor run capacitor by Dayton - oval, 2 terminal (C) InspectApediaThe questions & answers below discuss the wiring connections for electric motor start / run capacitor wiring as is typically found on heating & air conditioning systems as well as on other electric motors such as well pumps, sewage pumps, and electric shop tools.

These questions and replies were posted originally at HOW TO WIRE up a START CAPACITOR - topic home. Be sure to see the electric motor capacitor wiring help given there.

[Click to enlarge any image]

2017/08/27 (mod) said: what are the most-basic motor capacitor wire connections?

The standard wiring is in the HOW TO WIRE up a START CAPACITOR article where we give a live link above.

In addition there's usually a wiring diagram on a sticker inside the unit cabinet or on an access panel.

And if you have the I&O manual for your Carrier unit there'll be a wiring diagram there too.

Beware: there are fatal shock hazards working on that equipment.

2017/08/27 Don Hartel said:

A technician tested and removed the capacitor from my Carrier #38TZA042320 and told me to get a new one. I now have a new matching capacitor which says, Herm, fan and c which must be common. the wires he unplugged - 2, yellow 1, blue and 1, brown. I have no idea which color goes where. Can you help me?

(Aug 16, 2017) Derek said:
Would wiring a start/stop capacitor backwards cause a high pressure lockout over several hours in moderate temperatures? Thank you!

(July 31, 2017) Bjdidndnx said:
Hi I took off my capacitor and forgot were the wires go I have 1 yellow,1 brown,2 oranges. When I took off the capacitor I had only 1 orange connected I don't know if when the capacitor fried it blew off an orange wire or if I just don't need it I have a dual capacitor

On 2017-06-20 by Starr

I replacing my old motor with new the new has black white brown browm/white and gree├▒ I'm assuming is ground the old input purple to herm brown to fan orange to c and a orange from contactor to c

On 2017-06-18 by Cliff

I have a green house that gets really hot in the day time. I have an air conditioner unit that I took the compressor out of and am making a cooler using water pumped through the part that's left and am blowing air out through the top.

I still have the capacitor and I need to know how to wire the 220v single phase motor to it and do I even need the capacitor. I had it running but it started using only half of the 220 and running at half the speed. Help ?? Thanks

On 2017-03-25 by (mod) re: Woodtek drum sander wiring diagrams


I don't have a motor / capacitor wiring diagram for the Woodtek drum sander. Usually, if we've picked the right replacement capacitor and tested to confirm that it is in good condition, we would simply copy the original wiring connections on the tool.

In this case I'd suggest that you give Woodworker Supply a call to ask for their help: this is the customer support number 1-800-645-9292

or try

Woodtek® Parts and Machine Support 1-800-648-3953 x3038 Email: Eric Fairfield By Locations

Albuquerque, New Mexico 5604 Alameda Pl. NE Albuquerque, NM 87113 (505) 821-0500 FAX: (505) 821-7331 Operations Manager, Darrell Feldmann Email: Darrell Feldmann
(505) 797-1487 ext. 3033

Lisa Weesner, Customer Service Email: Lisa Weesner 1-800-231-2748, ext. 3074 505-797-1487, ext. 3074

On 2017-03-25 by Sam Waldner

Do you have directions (wiring diagram) on replacing dual starting capacitors on a 7.5 motor for a woodtek 37" drum sander?

My husband has been working for a week on trying to get the new capacitors installed and can't get it going. This machine is really needed.

On 2016-12-16 by Marty machado

Show me a wirering fora 1 do you please show me a wiring diagram for a third horse motor for a 0grinder

On 2016-08-13 by Anonymous

How do I wire an air compassator back onto my air conditioner. The words are scraped off

On 2016-06-22 by (mod) if motor won't spin, is it seized?

If you can't spin the motor easily that could be the trouble: does the motor hum? If so and if the starting cap is correct, the motor may be seized. Or if nothing, a wire or switch is open somewhere.

On 2016-06-22 by john

Looks like everything's got power,and hooked up,not running

On 2016-06-22 by (mod) re: rheem heat pump air conditioner

CHeck for power at the leads

On 2016-06-22 by john

Have a rheem heatpump, air conditioner, replaced capacitor, wired

won't come on, failed to write down before disconnecting. Is this right,could it be fuse?

On 2016-05-28 by pat

need "rewire" diagram for a/c capacitor

On 2016-03-03 by (mod) distance between a running or starting capacitor and the motor


I've seen the caps placed several feet from a motor, for example in some AC units and heat pumps. Placing the cap where the repair person can find it quickly is a bonus.

On 2016-03-01 by Bakkal

I'm trying to find something about the distance between a running or starting capacitor and the motor, anyone knows why they should be placed as near as to the motor?

On 2016-02-27 by David


On 2015-09-14 by (mod)

Thanks Gordon, you're quite right and I'll work on it; sometimes in a rush to put material online I've cc'd class notes that could indeed be more legible - and should be printed not scrawled. Apologies.

For now, if you [CLICK to ENLARGE ANY IMAGE ] or sketch or wiring diagram at InspectApedia you'll find displayed a larger, higher resolution version that is usually quite readable.

On 2015-09-13 by Gordon

Your wiring diagrams need that gentle touch of being typed out. No-one here could read your writing or understand the scrawled sketch. Sorry to be so negative, but on the good side everyone like your site.

On 2015-08-31 by (mod) I suspect perhaps a winding is shorting when the motor spins up to speed.


If the motor is a used one I suspect perhaps a winding is shorting when the motor spins up to speed.

On 2015-08-31 by Anonymous

I bought a single phase 1.5 hp motor with no power cord hooked up a cord under load it almost gets up to speed then it trips the circuit breaker on the motor what is wrong

On 2015-08-05 by Alibenari

I have a fridge which has a SK65CY compressor (80W running) which i would like to use off grid. The starting current is tripping inverter so I am using a Mars 171 potential relay and a 50microF Start capacitor.

The coil resistance of the compressor is 27 ohms and 43 ohms when measured from the common but I do not know which is the start and run windings. Can you please tell me if the compressor readings are correct and which should be the start winding? Thank you

On 2015-07-30 by (mod) Does putting a cover over a motor affect a capacitor


Millions of start/run capacitors are installed "under the covers" of electrical equipment such as air conditioning compress/condenser units.

But your question is a bit broad to permit a simple "no" answer. I can imagine some conditions in which adding a cover to equipment that was designed to be cooled by open air exposure could raise motor operating temperatures and thus may affect motor life as well as the life of components attached to the motor including capacitors.

So as the brilliant home inspector and educator Mark Cramer (Tampa FL) says, ''.... it depends"

On 2015-07-30 by Anonymous

Does putting a cover over a motor affect a capacitor

On 2015-05-19 by capcitor useges

How can i use capacitos in this motor.

On 2015-03-05 by Larry Dykshoorn

I have an old sears and roebuck bench grinder with a start capacitor it has 4 cloth insulated wires coming from windings. 1 wire was burnt off capacitor. can you tell me how it gets wired to capacitor and switch?

On 2014-10-02 by Anonymous


Question: fan will start but won't keep running.

(June 1, 2014) Anonymous said:

The fan on my Conquest 80 will not stay on (interior fan). It starts and then stops after a few seconds. It was installed in 2005. Help.



The start capacitor is for getting a motor started, not keeping it running.

Often motors have two windings, a start winding and a run winding. Your motor's run winding may be damaged.

Or your fan motor may require a dual capacitor (start and run) or a separate run capacitor to keep it spinning.

Or your system may have a faulty control.

Question: will a hard start capacitor reduce current drawn and stop tripping a breaker

(June 7, 2014) Joel said:

I have a commercial hood & exhaust fan (120v) running in a food truck that is used for catering. We occasionally need to run off a generator (3000w) and we've found that the fan cause the generator overload to trip.

The fan has been tested and observed to draw 8 amps running at full speed. Given this, would it be possible to add a hard start kit, such as SUPCO SPP4E? Will need to confirm the motor size, just wondering if this would help.

The total draw of all items is less than 20 amps and the generator is capable of supplying 25 amps constant.

Thanks for the advice.


Joel I think the problem lies elsewhere and needs some further diagnostics. I suspect that your total current draw is exceeding the ability of the generator - you may be running more than the fan, such as lighting, a cooler, toasters, other electrical appliances. If it were just the fan, drawing 8A, it has no business tripping the breaker.

Put another way if the problem is the fan and there are NO other appliances running, then there is a failing fan motor drawing high current, or an electrical short circuit or other unsafe condition to find and fix.

A start capacitor or a run capacitor won't change the current drawn by the motor.

Question: is it possible to rebuild a submersible well pump

(Feb 21, 2014) Anonymous said:

is it possible to rebuild a submersible well pump


Yes ... maybe; it depends on the condition of the pump casing, parts, an in my opinion, an accurate diagnosis of the trouble; at some point rebuilding is not cost effective. Indeed there are specialists (H Shreck in Poughkeepsie used to be one of them) who rebuild electric motors of all kinds.

There are also many water pumps whose design makes it quite reasonable to replace pump impellers.

So to answer your question, I dunno - it depends on what's broken.


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