Joelsheriff Posted March 8, 2022 Share Posted March 8, 2022 My 5yr old front 15k btu domestic is getting power and trying to start but it gets to a low hum for a long time struggling to turn the compressor on. Sometimes it just shuts down without any further action and once in a while you hear a puff and then a shut down. In either instance it never turns over into foul ac mode. What should I be looking at? TIA Link to comment Share on other sites More sharing options...
MrAmbassador Posted March 8, 2022 Share Posted March 8, 2022 Joel, two possible things come to mind. 1. The compressor is locked up (I don’t think this the problem, possible) 2. The capacitor has failed (this a common failure and much cheaper than #1). Check the capacitor. Be careful because they a an electrical charge. Hope this helps! 2 Link to comment Share on other sites More sharing options...
Ivan K Posted March 8, 2022 Share Posted March 8, 2022 I am with Jorge, if you hear a pressure release then the compressor has tried but could not overcome the pressure buildup and capacitor would be my first place to check out. Just short its posts with a screwdriver first, to kill any remaining charge after you get to it, with the AC breaker off. Link to comment Share on other sites More sharing options...
Larry Badger Posted March 8, 2022 Share Posted March 8, 2022 2 hours ago, Joelsheriff said: My 5yr old front 15k btu domestic is getting power and trying to start but it gets to a low hum for a long time struggling to turn the compressor on. Sometimes it just shuts down without any further action and once in a while you hear a puff and then a shut down. In either instance it never turns over into foul ac mode. What should I be looking at? TIA Sounds like the fan start capacitor needs replacing. $12.00 the last time I did it. Link to comment Share on other sites More sharing options...
Trinidaddave Posted March 8, 2022 Share Posted March 8, 2022 You may have and many of these units have a PTCT (Positive Temperature Coefficient Thermistor) failure. This device allows current to flow through the start winding on startup, and cuts out at approximately 75% of the full running speed of compressor. I did see this on my Dometic. Google this device for appearance and function. Link to comment Share on other sites More sharing options...
Larry Badger Posted March 8, 2022 Share Posted March 8, 2022 Fan start capacitor Link to comment Share on other sites More sharing options...
Joelsheriff Posted March 8, 2022 Author Share Posted March 8, 2022 Anyone with the knowledge of the capacitor I should order on Amazon. I found someone who will go up and replace it. It seems to be general consensus that it's the capacitor 99%. Thank you all Link to comment Share on other sites More sharing options...
Hypoxia Posted March 9, 2022 Share Posted March 9, 2022 (edited) 14 hours ago, Joelsheriff said: Anyone with the knowledge of the capacitor I should order on Amazon. I found someone who will go up and replace it. It seems to be general consensus that it's the capacitor 99%. Thank you all As Trinidaddave mentioned, the PTCR is also a likely suspect and is mounted on the start capacitor. PTCR I replaced all of my PTCR's with a Supco SPP6 as I believe they are more reliable. You can usually tell if the PTCR is going bad by smelling it, they turn stinky and look crispy. If your residential refrigerator quits working that's the first thing to check. My A/C parts manual lists the Compressor Start Capacitor and PTCR as "Compressor Start Kit" Capacitor Discussion Without the model number no one can tell you what capacitor is needed. When you eventually shop for the capacitor do not buy one Made in China unless you want to replace it again. MARS is one good brand. Edited March 9, 2022 by Hypoxia Link to comment Share on other sites More sharing options...
FishAR Posted March 9, 2022 Share Posted March 9, 2022 2 hours ago, Hypoxia said: As Trinidaddave mentioned, the PTCR is also a likely suspect and is mounted on the start capacitor. PTCR I replaced all of my PTCR's with a Supco SPP6 as I believe they are more reliable. You can usually tell if the PTCR is going bad by smelling it, they turn stinky and look crispy. If your residential refrigerator quits working that's the first thing to check. My A/C parts manual lists the Compressor Start Capacitor and PTCR as "Compressor Start Kit" Capacitor Discussion Without the model number no one can tell you what capacitor is needed. When you eventually shop for the capacitor do not buy one Made in China unless you want to replace it again. MARS is one good brand. I thought the spp6 was the entire hard start kit. I just replaced a capacitor and start motor with one in my rear #3 heat pump. Wired into the run capacitor. Link to comment Share on other sites More sharing options...
Larry Maida Posted March 9, 2022 Share Posted March 9, 2022 Check your freon Link to comment Share on other sites More sharing options...
Joelsheriff Posted March 10, 2022 Author Share Posted March 10, 2022 From what I'm getting, I suspect a capacitor, a fan motor and possibly PTCR separate from the capacitor. Is this right. Should I order the capacitor SPP6 and chance that the tech won't have to make a second trip out have him come down and diagnose all involved parts? Is this a good choice Supco SPP6E E Series Electronic Potential Relay Style Hard Start Kit, 1/2 - 3 Horsepower Range, 88-106F Capacitor Size https://www.amazon.com/dp/B002JP3MEK/ref=cm_sw_r_apan_glt_i_NHKC28ZDYCEYT24G1R8E Link to comment Share on other sites More sharing options...
Hypoxia Posted March 10, 2022 Share Posted March 10, 2022 IMHO, I would use a capacitor test meter to see what condition they are in but I have installed the SPP6 in every A/C unit on my last 4 campers. If the capacitor tests near 10% of the original value or worse I replace them. I always carry spare capacitors for the A/C unit and the residential refrigerator capacitor & PTCR. Link to comment Share on other sites More sharing options...
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