Carrier/Bryant Fan Motor ECM 2.5

[L_Euler]

I have a failed ECM on my HVAC air handler.  The control board that communicates with the thermostat and also signals the blower drive is PIC18F based.  On my unit (ECM 2.5) there are four signal wires and two 240VAC power wires going to the ECM.  I really want to set up a test fixture for this thing, but I can't find any background on the signaling between the control board and the ECM.  Also there appears to be some industry standards for ECMs, but apparently it is some state secret.  I can find devices that will test ECMs, but they are version dependent, 2.3, 2.5, 3.0, etc. and I can't find clarity on which one is which.  So my question:  Do any of you have understanding of ECM standards, if they exist, and what the signaling is?

[duak]

I have a Carrier furnace and heat pump system with the Infinity (Evolution for Bryant) control.  It works well and has some spiffy features but is apparently expensive to repair.  It's said of Carrier that you can always get better, but you can't pay more.

Anyhoo, I understand the Infinity control interface (ABCD or Communicating) is two lines for 24 VAC and two lines for bidirectional serial data with RS-485 levels.  It's a closed system and I've occasionally found dribs & drabs of info as experimenters have tried to reverse engineer it. eg: using "carrier infinity protocol" as a search term I find things like this:
https://forums.homeseer.com/forum/thermostat-hvac-plug-ins/thermostat-hvac-discussion/47625-anyone-talking-to-the-carrier-infinity-system
https://us.v-cdn.net/6031006/uploads/vbulletin_attachments/1/5/2/3/557.pdf

[L_Euler]

I have a Carrier furnace and heat pump system with the Infinity (Evolution for Bryant) control.  It works well and has some spiffy features but is apparently expensive to repair.  It's said of Carrier that you can always get better, but you can't pay more.

Anyhoo, I understand the Infinity control interface (ABCD or Communicating) is two lines for 24 VAC and two lines for bidirectional serial data with RS-485 levels.  It's a closed system and I've occasionally found dribs & drabs of info as experimenters have tried to reverse engineer it. eg: using "carrier infinity protocol" as a search term I find things like this:
https://forums.homeseer.com/forum/thermostat-hvac-plug-ins/thermostat-hvac-discussion/47625-anyone-talking-to-the-carrier-infinity-system
https://us.v-cdn.net/6031006/uploads/vbulletin_attachments/1/5/2/3/557.pdf

Thanks for the links.  Interesting stuff.  Communication from thermostat to local controller in air handler is solid, and controller to blower ECM is good, I assume.  I'm trying to understand the communication between the local controller and the ECM so that I can build a test fixture.  I have two of these units and I put a scope on the control line to the ECM of the known functioning unit.  The local controller communicates to the ECM with a serial link and looks to be transmitting two or three 8-bit words.  I need to understand the content of that serial transmission.

[kevinateev]

@L_Euler I just completed a diagnostic tool exactly for this.  It is on GitHub at : https://github.com/kpishere/Net485/tree/master/diag/net485Listen

It listens only.  There are a number of hardware options available to you to get RS485 to USB.  Check out the wiki in that repository for an example of my rig, easily available parts from China.