I have a carrier 8000 weathermaker its runs for 7to8 min then off and kicks back on in 3to 4 min

When did this start doing this? Have you done any work lately like a new stat or filter?

I have replaced the filter but still the same set at 69-70 runs 7-10 min then off and comes back on in 3-5 min

I just bought the house in dec 2010 the heater is 2002 the last three week we notice it cycleing on for 7to8 min then off and back on 5 min later house is 1958 the ducts are under the house

Looks like you started 3 different threads in 15 minutes but they are all the same question. Put your reply in the blank box below. In the meantime I will see if we can merge all this.

I have a carrier 8000 weather maker its runs for 7to8 min then off and kicks back on in 3to 4 min I bought the house DEC 2010 since then Ive notice it running 7to 8 min then off for 3to 5 min then back on I have change the filter nothing else

There should be a small clear window on the front panel aboutn the size of a egg, do you see it? Look inside, see any lights, how many, what color and what are they doing? These lights are threre to help diagnois a problem and there will be a chart inside the door telling you what each sequence of lights means.

Yellow light on steady

In your original, or follow-up post, you indicated the house was built in 1958. Depending on insulation, weatherstripping, leaks etc, your heat flow out of the house may be more than the heater can replace. How much insulation in attic? 16"? storm windows? At 0 outside and 68 inside, you have a substantial flow through an underinaulated house.

Not much insulation in roof plus steal roof wheni take off access door for under the house I get a lot of warm air

First home I've every own so I guess I have to learn the hard way the insulation in the roof is not that good but the heating is in the floor I do have storm windows and all wood floors and a steal roof if it matters thanks for the help I guess I have to spend more money

If you have warm air blowing down at you from the attic you may have a duct up there that has split open, I'd investigate. Your attice should be only a few degrees wrmer than the outside temp

Not in attic under house

My ducts are under house

If you don't have "much" insulation, I'd blow in at least 16" and see if that doesn't help a lot. You can get a free blower at HD and Lowe's if you buy the insulation there.

Ignore me, I just reread mypost which makes no sense to me now. I thought you said when you opened your attic door warm air poured out. I must have mixed your post with someone else, my bad. Were you in this home last winter, how did the furnace act then? Where do you live and what's the night temps

Says he bought the house Dec2010.

I just bought dec2010 moved from calif

Is duct work in the crawl space insulated. What Bob said about attic also applied to crawl space. To feel the heat when you open the access door sounds like disconnected duct work.

Check area where thermostat is located. Either you are losing heat from your house very fast or you have a supply vent blowing warm air on the thermostat tricking it in to shutting off.

Right, I knew I read something about opening a door and lots of warm air. Duct in crawl and warm air coming out of crawl could be open duct somewhere.

I went under house and found the air pendlem box rusted out on bottom

Thermostat wear you set the temp is in hallway it shows 69 on both side it donest drop before it kicks back on

Fix the plunum and most all of your issues will go away. You can patch it but a contractor will have insulated duct material and tools to do the job. I'd get 3 bids from contractors before tackling it myself.