Circuit Boards

[pcairetech]

Hey guys, need some advice on circuit boards. A/C unit keeps shutting down intermittenly, checked for short and loose wires, can't find anything. Checked thermostat when the unit turns off and I have no 24VAC. Checked incoming power to unit (xfmr) when it's off and I have 120VAC. The indicator LED on board was off , then all of a sudden it will come on???? I think it's the circuit board and that's what I told my customer as well, ofcourse if it's not well then it's going to cost me to make it right, that goes without saying. Just want some input, i've never seen a circuit board do that, usually when it's out, it's out. When it runs, everything is good, it'll run for about 10 mins and shut down. It's like something is opening then resets by itself? I've already applied for Pro membership, hopefully mods will let me post this here. Thanks guys

[bmathews]

The last time I checked, a transformer has 2 voltages. That is what it's name implies. Is the board between the transformer and thermostat? The board is a power in/power out sort of deal.

[Twilly]

Twilli say they'll let you.

[pcairetech]

Thanks Twilli

[pcairetech]

The last time I checked, a transformer has 2 voltages. That is what it's name implies. Is the board between the transformer and thermostat? The board is a power in/power out sort of deal.

Will a xfmr heat up and reset itself? I've seen that happen with heaters on starters when set on automatic but never a xfmr

[model m-man]

You're a tech. Follow the power flow. Think about what powers the thermostat and then think about what powers the board. First thing's first. Not allowed to get any clearer untill you move over to the other side.

[pcairetech]

Yeah you guys are right!! The t-stat is what controls, therefore it would tell the board what to do, If I have no control voltage to the t-stat, that means I need to take a closer look at my transformer and power source, Thanks guys

[pcairetech]

Hey guys just to update, it was the disconnect. Wire was loose on the terminal. When I pulled it out, the wire jumped out at me, I had the power off lol!! Thanks for your input. My customer was very happy and i was hero today, after being a zero last night!