Thanks for sharing my friend. Hey how do I tell which is start and which is run. Our shop air compressor has 3 capacitors. It doesnt like to start under a load. Or wont start I should say.
they are of a compressor that starts but when its full the motor cant or wont turn over to recharge .it start first of when no presure is in it . if theses are gone why would it start first to charge the tank? .
Ok Ive identified the start cap. All 3 read correctly in cap test mode on my multimeter. And in ohms mode the 2 other caps got a quick readind and went to infinity. After a few reads though they quit reading ohms only infinity. Are they both bad?
Performing readings on a capacitors while your multimeter is in the ohms/resistance mode/scale, won't really tell you if the capacitor has the right capacity (uF wise) but could potentially indicate if there is a short. When using the multimeter in ohms/resistance mode, the multimeter actually applies a small voltage to the device connected to the probes and measures the resulting current. What you see on your meter is actually a visual representation of that current. By nature, discharged capacitors will behave like a short (very small resistance) and present more and more resistance to the current flow as they charge. When they're fully charged or reach the source voltage, in this case the voltage applied by the multimeter to measure the resistance, the capacitor doesn't allow anymore current to flow, thus your meter is showing a very large resistance (pretty much infinity). If you discharge the capacitor, by connecting a resistor or possibly shorting the pins for few seconds, you could repeat the steps you did, taking multiple reading while in the ohm/resistance mode, and you will pretty much end up with the same results which indicates that the capacitor(s) are charging and keeping their charge. If you let the capacitor discharge by itself, without shorting the leads that is, and take another reading at a later time, this could help you qualitatively determine how good the capacitor is capable of keeping its charge. If the capacitor keeps its charge adequately, you should be able to make another reading some time later and the reading should be very close to infinity. If the resistance is low then increases afterwards, that would indicate that there is some current leakage, potentially indicating that the capacitor needs to be replaced. Once again, this approach isn't perfect, but when you actually understand what's going on behind the scene, it's easier to troubleshoot in a more efficient way.
So would a reading of 6.8 be to low for a 7.5 uf 370 vac run capacitor ? There is no info about a 5% difference. I have a rv ac that hums when I turn on , I can spin and it will run for a while then slow down and stop., I tested start capacitor and it's new and within spec.,
