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Old 04-27-2009, 04:40 PM   #1
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ac contactor replacement and run capacitor discharge


Hi all,

I have a rheems ac unit. I am thinking of replacing my ac contactor on the condenser outside though it is still working fine (been there almost 9 years). I understand I must cut off 240 volts and turn off thermostat for it before I start.

My question is whether simply use insulated pliers to pull off all the wires to the contactors (lines and terminals) is good enough ? As on the terminal side, it has connected to a run/start capacitor or should I discharge the cap first before working on the contactor replacement ?

If need to discharge cap, can I do it with all the wire-in-place using a big insulated screwdriver or I have to disconnect the wire first ?

Thanks all so much in advance.

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Old 04-27-2009, 08:16 PM   #2
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ac contactor replacement and run capacitor discharge


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Originally Posted by rheems88 View Post
replacing my ac contactor on the condenser outside though it is still working fine (been there almost 9 years).

At rated current, if the voltage across the closed contacts is less than 30 mV they're good. Above 100 mV, bad.


If need to discharge cap, can I do it with all the wire-in-place using a big insulated screwdriver
Don't short it with a screwdriver. Grainger sells a 15k, 2w resistor for this purpose. Buy one at Radio Shack.

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Old 04-28-2009, 10:07 AM   #3
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ac contactor replacement and run capacitor discharge


thanks for your reply. I will use resistor for this, but can I do it with all the wires in-place ? or even better, can I not touch the cap at all (simply remove the connector and replace the contactor and put the connector back) ?

thanks again.
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Old 04-28-2009, 10:15 AM   #4
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ac contactor replacement and run capacitor discharge


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Originally Posted by rheems88 View Post
can I not touch the cap at all (simply remove the connector and replace the contactor and put the connector back) ?

thanks again.
Yes, just tape over the cap terminals if there is a chance of touching them.

You know, anytime you mess around with something that's working [or not] there is a non-zero chance that something else will stop working, either because of operator error [like dropping a conductive tool into the works] or because of some baffling problem that suddenly springs up and that may or may not be related to your work.
I wouldn't mess with this unless you are having a problem, especially not if your relay contacts pass muster. Monitoring parts health is less risky than replacing parts.
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Old 04-28-2009, 10:55 AM   #5
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ac contactor replacement and run capacitor discharge


thanks a lot for your time and replies. Those are very wise advice. I will take your advice and stay alert on it (rather than messing with it).
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