check voltages... ELCB for A/C keeps popping - Page 1
Forum section: electronics / beginners

author: fleuroman
author_rank: Contributor
timestamp: November 22, 2015, 10:24:01 am
content: during winter, the home A/C stopped working, kept pulling the Earth Leakage Circuit Breaker, anyhow... no problem... it was winter. but... but Friday the mercury topped 41C here... so, how to check voltages, when the power keeps disconnecting, on a 1.5 circuit, a 9v circuit etc, no probs, but 240v @ 50Hz...so, I removed the top cover of the outdoor unit, and the small cover where the mains come in and out, to the indoor unit, it has a basic (and I mean basic) circuit diagram... there's 3 boards... wires everywhere, some wires with 1/4" spade connectors on a secondary board have been getting very hot at the connector, and same on what they are calling a rectifier... I'm thinking, how do I check voltages when I cant keep voltage to it... so, Im thinking... lets try a process of elimination... the most likely thing are fan and compressor... I carefully disconnect the fan connectors from the main pcb... turn power on... pop... nope... disconnect the compressor, power on... pop... ok... so neither of them is shorted to neutral, I disconnect the two power connectors to the secondary board that have been hot... power on... it stays on... hmmm... ok... power off... time to be careful... caps will have charged... nothing on this secondary board looks damaged/burnt, none of the big round caps on the main power board have "expanded"... I'm reconnecting the secondary board, and it arcs every time I touch the earth to the connector... caps discharging or the short... I still want to try the rectifier... disconnect the two hot/burnt looking connectors... power on, again, it stays on, well, that secondary board must be ok, its all connected... the earth on the rectifier has been hot, along with a white wire that goes back to the main power board, the power wire is still on the rectifier, so its not an internal short... power off again, reconnect the earth to the rectifier, maybe its shorting internally... power on... it stays on... power off again... ok, it has to be the main power board, the white wire, trusty Fluke multimeter, measure to ground and neutral... dead short... there's this big black box on the main board, I thought was a relay... it's a cap... and its expanding... so, now to find a replacement cap...

author: crispy_tofu
author_rank: Super Contributor
timestamp: November 22, 2015, 11:19:40 am
content: Aha!Congratulations.

author: fleuroman
author_rank: Contributor
timestamp: November 23, 2015, 05:03:43 am
content: I had to replace the rectifier Toooooo... but yeah... quoted 3,000 to replace the complete 7 year old A/C... fixed for under $30...

author: fubar.gr
author_rank: Unknown
timestamp: November 23, 2015, 02:22:06 pm
content: The golden rule in troubleshooting is to check voltages first, but this is not the case here.A tripping earth leakage device (RCD, GFCI or whatever you call it in your corner of the world), is a problem that has very specific causes and has nothing to do with voltages.You solve such problems by identifying and testing any point where the mains carrying parts can come into contact with an earthed part.In your case it seems the problem was a faulty Y cap.