furnace has short heating cycles

[dafish76]

Hello i need some help please with my furnace i have a coleman blend air model # 7970-590 my problem is when i turn on my furnance it will come on and run for about 1 min. than shut off and it keeps cycling like this evan if i turn up the thermostat to 85 last winter we were having a problem with the heat cool switch on the bottom of the theromstat some times the furnance wouldnt come on and you would have to move the switch from off to heat then it would come on i was just wondering if it is the thermostat doing this now or what i need to check Thankyou for your help

[Robert]

Hi,

That is the blower assembly number. It could be the t-stat, limits, fan & Limit, loose connections to name most common.



Thanks,
Robert

[dafish76]

Thankyou for your response sorry the model #of coleman furnance i have is 7966-856 do you have the theromastat i need for this furnance i also have ac. the thermostat i have now is a miller and i have 4 wires comming out of the wall and they went to treminals rh-w-rc-y i will check for loose connections can you tell me how to check the limit switches i do have a d.v.o.m once again Thankyou for your time

[Robert]

Do you not have a green wire connected to G terminal on t-stat ?


Should have that for blower operation in a/c mode.


Thanks,
Robert