My AC system is getting very old and I was wondering if I should add a Hard Start kit and with what spec? Here is my AC spec included below and the existing Dual Run Capacitor is 440volt and 40+5MFD.

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  • Noting that it uses R-22 freon, you'll need to start saving for a new system. R-22 Freon went out of production January 1 this year, and the only source for the stuff is what's being vampired and recycled/reprocessed out of old systems coming out of service. This is making the price of the freon go ballistic. Aug 12 '20 at 3:49
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    @ Harper there is still new virgin r22 available it just cannot be imported or manufactured any longer. I bought a jug last week the price has continued up but still available $380 for 30 lbs. Cyrus why do you want a hard start cap? Are you having problems with the unit blowing fuses or dimming the lights on start up? If so order a new cap and replace it with a 40 +5uf rated at 440v it is a common size and a GEnteq is available online for 15.93 on amazon free shipping. If not the cap it could be the contactor if there is a problem.
    – Ed Beal
    Aug 12 '20 at 14:35

Should you just change a cap because your system is old? NO you don’t state there are any problems. Electrolytic capacitors do fail over time but we don’t know what you have. oil filled usually last the life of the unit but are much more expensive and not appropriate for all climates.

If you are noticing the lights dimming , hard starts blowing fuses if all the connections are good replace the cap with the same value.

As electrolytic caps age they loose their ability to hold a charge and or short out (note a bulged cap case has usually shorted, it may be working now but needs to be replaced). As caps loose their ability to hold a charge they can not get the motor started thus dimming lights and blown fuses, let this go in long and the compressor windings will be damaged.

There are lots of film flam guys out there if your system is starting hard the cap just needs replacing with the same size it is that simple (if the cap is the problem). If you could not find the same size +-10% will work but not as well as the manufacturers recommended size.


I also have a 3.5 ton R-22 unit. Mine (a Carrier 12 SEER with a scroll compressor) has been in service for 29 years and is coming to the end of its service life. I am trying to get through one more cooling season but my refrigerant is low judging by the sight glass and the fact that the suction line is not as cold as I think it should be. I figure that I could need a full replacement any day.

I see no reason why you should add a special start kit. Do you have any reason to think it would functionally benefit from this? It won't be cheap.

  • Jim do you have a bunch of bubbles? If so a charge now may keep your unit running another 5 years I wish they still put sight glasses on systems quick and easy to tell the charge level. But your answer is more of a comment.
    – Ed Beal
    Aug 12 '20 at 14:38
  • More than just bubbles in the sight glass--I can see gas over flowing liquid on the bottom. Either that or lots of bubbles. I am surprised that it is still cooling, but it is maintaining 75 F and the high yesterday was 100 F. 102 F predicted for today, 90 F right now at 10 am in Dallas. I must have a slow leak. I am torn between calling the a/c service to get a top off. One tech told me that the sight glass has an elastomer seal and is a risk for a leak. Aug 12 '20 at 15:22
  • Yes this is why they quit installing the sight glasses. But they were a quick and easy way to verify the charge, I just saw a 35 oz can on line for 68$ with the connector. Dealer in El Paso I was double checking what I paid was actually 345 but those deals are getting rare. You should get your level 1 card on line then you could get a couple of those 3 lb cans and keep your system running for another 10 years, mainstream engineering has a level 1 online corse that would let you service a 5 lb system legally (I don’t think the rules have changed)
    – Ed Beal
    Aug 12 '20 at 15:24
  • My system is factory charged at 10.93 lb (4.96 kg). Aug 12 '20 at 15:38
  • Ok I was thinking the op’s system yours may take 5 or 6 lb for a full charge.
    – Ed Beal
    Aug 12 '20 at 15:45

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