I have read several postings on here about this subject, but have not really found the answer to my problem. I am having similar trouble with my relatively new RTH230B Thermostat (Mainly the A/C won't work properly). I installed it this past fall and my gas furnace worked like a charm. However, the other day I went to switch to A/C and nothing happened. When trying to rewire it this morning, I was able to get the A/C unit to kick on (after several minutes), but not the blower. I replaced a Totaline P374-0200 with this model. I have 7 wires to deal with (W,O,G,R,Y,Blu,Blk). I can't remember but I think all but the Blk wire was used on the totaline model. I am currently using the 4-wire Heating and Cooling set-up as shown in section 2.3.5 of the installation manual. Does anyone know what I need to do to get the A/C unit and blower to work properly?

My set-up:
Red wire jumpered to both Rh and Rc (I assume this is power)
White to W (Heat relay)
Yellow to Y (Cool relay)
Green to G (Fan Relay)

Thanks,

This tstat is apparently stressing quite a few people out. I started my day with a similar problem. I turned my cooling mode on and nothing. I have the same model Tstat.

My HVAC system is gas fired furnace with an outdoor A/C unit. I have 5 wires coming up from my low voltage panel (in the furnace) to my programmable thermostat. I initially set it up as a 5-wire setup (made sense to me anyway). Well, today I ended up placing the jumper back in the Rc & Rh, keeping the red wire hooked up and removing the blue wire from the Rc connection. The other wires (white, yellow, & green) remained connected to the tstat. This appears to have solved my problem.

Now, you have an additional black and orange wire. I believe these wires are for sending a signal to the low voltage panel in the furnace to modulate the fan for part load conditions. You may want to trace these wire back to the panel in your furnace. I know that on the RTH230B Thermostat packaging, it indicates that the thermostat is not compatible with multi stage heating and cooling. This may be the issue if that's what you have.

What was the wiring config on the Totaline P374-0200? Did the orange wire have it's own connection at the thermostat? I understand you can't recall the black wire though.

Do you have an outdoor unit which provides cooling?

Bison,

I spent much of yesterday stressing over this tstat. I traced the blk, orange and brown (which I forgot) back to the furnace and found that they aren't used at all. I believe the blue is connected to ground from the outside A/C condensing unit. I figured this out by blowing a couple of fuses on the furnace yesterday when touching the red and blue together. I have mine connected the same way you do right now and it is working for the moment (thought I'm not sure how long). I'm not sure what is different from the way I had it connected yesterday morning when the blower wasn't kicking on, and the way I have it connected now. I did take the whole thermostat apart and I think there is definitely something wrong with an internal relay. I had everything connected and away from the wall and just by rotating my hand one way the A/C unit would kick on... and the other way it would kick off. I am calling Honeywell on Monday and will try and get them to upgrade my model. As for right now, I am getting lucky. Although the fan doesn't work at all when switching it from auto to on. Not sure what to do about that.

Thanks,
Marcus

Good luck with Honeywell.