[dholly]

Hi all:

Came aboard looking for info after getting a blank display on our Carrier thermostat. Had been running A/C for a few days and noticed inside temp was not holding. In fact, I found it wasn't running at all and the t'stat display was blank.

I also found circuit breakers in both the main panel and the on-unit panel tripped. Resetting the breakers had no effect, though they did not re-trip. A visible check for broken or loose wires came up empty, and no anomalies in the t'stat, air handler or outside cooling unit and their circuit boards were evident.

The main panel automotive style blade fuse is intact, and jumping the R to G terminals at the t'stat to test the fan gets no response. So, based on what I picked up in the DIY archives here, I have either a faulty thermostat or a bad transformer in the air handler.

Unfortunately, I don't have a 24v multimeter to read voltage across the R and C terminals at the t'stat, Are there any other 'meterless' DIY tests I might do to help identify the culprit? Last, assuming it is a bad transformer, what kind and where abouts are they to be found?

Any help appreciated, thanks in advance.