AC Contactor Troubleshooting Guide Step By Step (Contactor Not Pulling In)

ac contactor troubleshooting

So you think there’s a problem with your AC contactor and you want to troubleshoot it yourself. Because you got a high price quote from the AC technician. I know it can be pretty frustrating when repair companies quote a very high amount for a tiny repair.

So In this article, I’ll take you through a step-by-step process of How you can troubleshoot your AC Contactor and what’re the major problems that occur in the ac contactor, and also why your ac contactor is not pulling in.   

How much does an AC Contactor Costs?

On average AC contactors can cost between $5-$40 depending upon the size and number of contacts. Most of the AC uses a single-pole contactor and they’re pretty inexpensive to get so don’t stress over it. 

Problems that may occur with Your contactor:

1: So problem number one is when the contactor is stuck in the closed position and this happens when the contacts are welded together just due to high amperage so they melted and fuse together.

2. Problem number 2 is when you have a high resistance reading across the contacts and that could be due to some of the pitting on the actual contacts themselves inside and they’re just not making a connection.

3. Sometimes bugs will crawl in like an ant or some kind of beetle will cropland in between the contacts and the metal strip. So when the contactor gets magnetized and tries to pull in the bug will prevent it from closing all the way.

4. Sometimes the contacts themselves get worn out to the point where they don’t make contact and it can result in a non-working contactor.

5. Problem number 5 occurs when your electrical connections will not be properly fitted on the tines of the contactor. And if the wires are not properly fitted your contactor will not get any power. So make sure to check your connections.

Troubleshooting Your AC Contactor

Step 1: Turn Off The Disconnect Switch

The first thing you should do is cut the power from the disconnect switch to your ac. Because if you operate the contactor while the power is ON. You might end up getting electrocuted. 

Step 2: Locate Your Contactor In The Condenser Unit

locate your contactor

Now you need to locate your contactor on the condenser unit. Most of the time your contractor will be on the side panel of the condenser unit. You just need to follow the electric whip that’s coming from your disconnect switch. Just remove the side panel of the unit with a screwdriver and access your contactor.

Step 3: Turn Your Thermostat On And Test Your Contactor Voltage

testing contactor

One thing you should know is that your contactor doesn’t draw power from the condenser disconnect switch. It actually draws power from the furnace through the thermostat. 

Now you need to turn your thermostat ON and set it cooling. Then just go outside and check if your contactor is getting the voltage from the thermostat. Put your meter needle on the contactor pins where the thermostat wires are connected. Now check if you’re getting the proper voltage or not. It should be anywhere from 24 to 29Votls.

Step 4: Try To Pull your Contactor Manually

manual pulling contactor

Now if you’re getting the proper voltage from the thermostat and still your contactor is not pulling in. Then there’s a problem with your contactor. Maybe there’s an insect in between the contacts and it’s stopping your contactor from pulling in or maybe the contacts are just worn out and that’s why they’re not pulling in. 

Just try this one thing (Make sure you’re following proper safety measures don’t touch anything after the Power goes ON. It can be fatal) 

Turn your disconnect switch On and Take an insulated screwdriver and try to push the contactor’s contact pin and see if it’s working or not. If the contactor starts working then you have a contact/plunger issue. And if it’s still not pulling in then maybe your contactor coil is just burnt out. You need to replace that contactor.   

Top 6 Why Your Contactor is Not Pulling in? 


1 Your Furnace Switch is OFF:

Reason number one why your contactor plunger may not be pulling in is because your furnace power switch is off. Maybe you were changing the filter and it got bumped off or maybe some kids were playing around and turned it off.

If your blower motor is not working then you should put the contactor on the hold and go figure out why your fan’s not working first before you deal with the contactor.

If your furnace is not getting power because that power switch is off that means the control board’s not getting power. Therefore it’s not going to send anything outside to the contactor.

Check Our Furnace Repair and troubleshooting tutorial

2. Tripped Condensate Overflow Switch

Reason number two is a condensate overflow switch. Sometimes if your drain line is plugged and the water is backing up and the water will go up and trip the overflow switch and kill the power to it. So if you have a condensate overflow switch check that out and make sure your drain is not plugged up. 

3. Check Your Thermostat

Reason number three is a bad thermostat or a thermostat working incorrectly. Now I say working incorrectly because perhaps it could just be dead or weak batteries.

When batteries are weak your display will still be on but the batteries don’t have enough power to close the switch to make a call for cooling. So if your thermostat has batteries try replacing those.

Another thing I’ve seen is the connectors behind there are loose or sometimes a wire is just broken off altogether. So pull your thermostat off the wall and just try gently tugging on each wire and make sure that each one of them is making a good connection.

And if you have recently replaced your thermostat and you have an R and Rc pin on the thermostat. So make sure you have a jumper between R and Rc. Because R means power and Rc means power for cooling.

So if you don’t have a jumper between the two you have no power for cooling. And another reason is your thermostat could just simply be bad and an easy way to find out if it’s bad or not is just to bypass it either at the thermostat or at the control board. I have a full tutorial on bypassing the thermostat you can check it out.

4. Bad Wiring

Reason number four is bad wiring and what I mean by that is bad wire connectors, bare wires, corroded wires, broken or melted wires. So investigate all your wires before replacing a blown fuse.

5. Bad Control Board

Reason number five is a bad control board in the furnace. If your control board is not sending power to the outdoor unit then first inspect the control board then go for the contactor. 

6. Bad Power Saver Switch

Reason number six is a bad power saver switch. This switch will not be at all the houses but if you do have it. So what that does is on really hot days the electric company cycles people on and off sporadically.

Because not everybody is running their ac at the same time and companies give you like 10 or 15 bucks off a month for doing that. But sometimes this power saver switch can become defective. You can just call an AC technician or the power saver company to sort it out.

Click Here To Check Our AC Repair Troubleshooting Tutorial

How To Replace Your Contactor?

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