RV Repair: air conditioner thermostat, air conditioner thermostat, fan operation

Question
we're not sure if we ever used the 2 speed function for the fan.  The replacement thermostat was a coleman 7900-7541 and it has red, white, green, and yellow wire.  The AC unit is I think a MACH1 7332 series or possibly a MACH3 7333 series.  Hope this helps.   Gary
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Followup To

Question -
We were having trouble with our AC not shutting down after a while.  We took out the old thermostat( Coleman 6799C6951) and recorded what went where.  It has six wires coming out, white, red, grey, yellow, blue, and green.  The replacement one we got only has 4 wires, white, red, yellow and blue.  Not sure what goes where.  The original therm. is for heating and cooling with high and low fan.  Any suggestions would be appreciated.    Gary

Answer -
Hi Gary:

It sounds like they may have sold you the wrong thermostat. Your origional thermostat has provisions for a two speed indoor fan operation. The new thermostat does not have that option. Do you know if your air conditioner uses the two speed indoor fan function? Would you please send me the part number of the replacement thermostat and if available the model number of you air conditioning unit, so that I can do further research on this matter for you. I will do my best to assist you any way I can.

Regards, Larry

Answer
Hello Gary:

I appologize for taking so long to get back with you. Ive truly been looking for the correct wiring diagram, so I could compare the two thermostats to determine if the replacement would work. I did not want to give you a short, incomplete answer. I wanted to be able to tell you why. After lots of research, the short answer is no, it will not work. You will need the exact replacement for the original one. The new one you have does not have a green or gray terminal. The green wire sends a signal for the fan start on at high speed. The gray wire sends a signal to start the fan on low speed. You can see why these two additional wire terminals are necessary. Without them, the a/c fan would not come on.

I hope this helps out. If I can further assist you, please let me know.

Regards, Larry