Central AC issue and few questions

[MEDTECH]

I have a heil/ICP unit that is 25 yrs old and part of a forced air system. 2 days ago, the unit stopped working; no compressor, no fan and no noise or humming can be heard from the outside unit. I have no experience with HVAC but I tried the easiest remedy which was to replace the dual capacitor, carefully checked my connections to HERM, FAN, COM and no luck. Had a handy friend take a look and he tested voltages on the contactor and all values are good. The contactors plunger had to be pressed in and the compressor did come on but not the fan. Coolant line was cold so that seems ok. Just curious while I wait for my tech to come, can this be a bad fan motor? Hi or low pressure switch engaged? Just trying to learn what else can cause the fan not to spin. Even replaced thermostat batteries to rule that out, too. Thanks for your insight. Also checked the breakers, always replace filters every 3mos or less, condensate drain was discharging as it should, etc.

 

[acmikee]

did he check for 24V at the contactor. could be locked out on the control circuit--try cycling the power on the condensing unit. add a jumper wire on R to Y and see if the unit comes on....

 

[MEDTECH]

did he check for 24V at the contactor. could be locked out on the control circuit--try cycling the power on the condensing unit. add a jumper wire on R to Y and see if the unit comes on....

Yes, he was reading about 26.5 V @ the contactor. We did all our tests @ midnight after work so not the best condition to really dig further. Hopefully, my tech squeezes me in tomorrow. In the meantime ceiling fans and water. My buddy is not in the trades but he has a great understanding of schematics and how things work in general. Used to do ALL of his home and auto repairs, upgrades until the divorce

 

[Milton Shaw]

Sounds like you have a bad coil on the contactor. If if has 24 volts then it should be pulled in. I would suggest checking ohms on the coil and then probably replace the contactor.

 

[htmdude57]

If you had 26V on the contactor, but you need to manually push it to make compressor come on, that sounds to me like the contactor is bad? As far as the air fan- try using a screwdriver through the cage to give it a push. Maybe it is stuck?

 

[MEDTECH]

That's what my tech was thinking as a first solution to try, too. But, I'm not sure why, after manually pushing the plunger, the compressor came on but not the fan. And I also tried to start the fan manually by using a long wooden ruler. Blade spins freely but doesn't actually come on. Please excuse my ignorance as I am new to this and learning on the fly

 

[htmdude57]

I guess the next step is to use the ohm meter, as Milton said, to see if the coil on the contactor is open. Then get the numbers off it and order one. As far as the fan, same process- check if voltage is getting to its wires, after the compressor is running. Also, look for a schematic diagram glued inside the unit. It may have the contactor number? It may show if there is a capacitor in the fan motor circuit?

 

[acmikee]

bad coil on the contactor.
check your wiring diagram and for the fan it might be on a separate relay

 

[fitter30]

Fan might have a pressure control in line with the fan motor. Contactor should of pulled in with 26 volts. Fan motor with power off does it turn easily? Do you have a ohm meter and or a amp meter? Ohm out the motor 1x they have internal thermal overload. Amp meter low setting 0 to 20 measure capacitor wire when pushing in contactor if motor ohms out it should read something if cap is good. Never replace a motor without a new capacitor.

 

[MEDTECH]

Fan might have a pressure control in line with the fan motor. Contactor should of pulled in with 26 volts. Fan motor with power off does it turn easily? Do you have a ohm meter and or a amp meter? Ohm out the motor 1x they have internal thermal overload. Amp meter low setting 0 to 20 measure capacitor wire when pushing in contactor if motor ohms out it should read something if cap is good. Never replace a motor without a new capacitor.

Fan blade turns with long stick but doesn't power up. I can check more tomorrow before tech comes. Not home now which is good because it was 90 inside AND out by me. Enjoy your 4th and be safe. PS Installed new capacitor yesterday hoping for a quick solution but no dice