Only getting 18 volts at contactor input


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Old 05-06-14, 05:59 PM
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Only getting 18 volts at contactor input

Squirrel fan running - but the main outdoor fan doesn't turn on. Its a package unit.

Only getting 18 volts at contactor input & nothing for output.

Thanks.
 
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Old 05-06-14, 06:14 PM
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Welcome to the forums.

On a contactor you have the L1 and L2 terminals where the 240vac comes in on one side of the contactor. Then you have T1 and T2 on the other side of the contactor where the 240vac comes on when the contactor is activated. The two small wires.... one on each side of the contactor are the coil wires. They should be 24vac.... not 18vac.
 
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Old 05-06-14, 06:43 PM
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welcome--and PJMax knows his stuff--just went through that myself and he and others helped me out.
 
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Old 05-06-14, 07:38 PM
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Hi,

Thanks for helping!

YEs L1 & L2 is what I was referring to - mine are both black wires on a 4 ton Goodman package unit.

...and T1 & T2 were showing < .5 v.

Also, the coils weren't cold - so I guess compressor wasn't running either.
 
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Old 05-06-14, 08:02 PM
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Voltage can vary. During "peak demand" I've tested downtown building voltages and have found it as low as 100 volts ac. Equipment don't like it but do operate. There is a voltage transformer inside electrical control panel. Be it gas heat it will be 120/24 volt transformer. Electric heat 240/24 volt transformer. You say squirrel cage is running can you here compressor running. If both online secure power and spin fan is it free spinning. If fan is free check it's capacitor. Is it expanded hot or dis figured in any way. A micro fared check can be performed if you have mfd multimeter. If not mfd meter type place multimeter in ohms setting. Power still secured Place screwdriver between terminals on capacitor. POWER IS SECURED WHILE DOING THIS. Screwdriver will discharge capacitor if voltage is stored in it. Unplug wires from cap terminals put meter leads to terminal post of capacitor. If meter ramps up then back down reverse meter leads at terminals and see if it ramps and drops again. If it does ramp up an down capacitor is good. Ac techs will sometimes approach unit with power applied use screwdriver to spin fan thru housing. If fan begins to operate that proves capacitor is bad. If capacitor proves good and fan does not start screwdriver spin it is possible fan motor failure. Understand this is electrical device can and will KILL you. Do not attempt anything you are unsure of and I assume no LIABILITY for advice given. If in doubt call a professional. Always remember if the world didn't suck we'd all fall off. Good luck friend.
 
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Old 05-06-14, 09:58 PM
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Did you measure/find 240vac on the L1 and L2 terminals ?
Double check the contactor coil voltage that you previously measured 18v on.
18vac is an unusual voltage. Usually it's very near 24vac or very near to 0v. It could mean that you have a failing safety switch or even control transformer.
 
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Old 05-07-14, 05:58 AM
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The main capacitor looks good - 30a on all 3 points.

Tripple checked inputs on contactor - 18 to 18.5 all times.

Any other ideas ?
 
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Old 05-07-14, 07:56 AM
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We are going around in circles here.

What voltage did you get on L1 and L2 ?
What voltage did you get on the 24vac coil connections ?
 
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Old 05-07-14, 09:46 AM
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Again, on L1 & L2 inputs together I got 18 to 18.5 vols only.

...and nothing on output.

I do not recall the exact # on the Vac - but seemed to be higher.

This is not my property btw - so I have to drive out there.
 
 

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