Why is this furnace locking out??

[GJ-HVAC/R]

On a no heat call today. Furnace locking out on high limit. Went to check filter and found none. Checked evaporator coil, and turns out, its slightly dirty!!! Homeowner has lived there seven years and never knew about a filter. Worst part is that someone was out last month. And replaced the flame sensor. And a year ago someone found a "problem with the gas pressure"!!! When i pumped the system down to remove coil, i got a look at the condenser coil! First pic is evap, second is condenser. Btw, they have dogs.

[chaard]

Had a customer awhile back. No filter rack. Return grilles just grilles. No filter ever installed in the 7yrs it was built. Evap coil and blower were clean. I was amazed.

[sweat hog]

It made its own filter.

[tunnel_rat]

Holy Moses........!!I think I know them....

[ryan1088]

Another filter type that gets more efficient with time!!!

[OldSchoolMech]

That Filter stops everything sensible, latent heat etc LOL

[DoctorCool]

wow... how can that system function just how?!

[WarTurtle]

Must be renters

[Cooked]

When I saw the first pic I thought it was a tear in the "time-space continuum"

[GJ-HVAC/R]

Must be renters

I would have thought so too, but its not

[71CHOPS]

now that you cleaned it, the whole system is gonna die.

[ryan1088]

now that you cleaned it, the whole system is gonna die.

At least the blower motor will.

I had that happen to me once, cleaned the filthiest condenser I had ever seen, compressor locked up the next day.

[mrpogo]

I was on a no heat got there and airhandler was running but barely a wisper of air coming out the vents. I went to check the airhandler filter had not been changed since 2008. When I pulled the filter and you could hear the blower say ahhhh. 2 weeks later we were back to replace the motor.