What's good everyone how's it goin? 2001 Honda Civic LX 5-Speed lil over 174,900 miles. The heater core has stopped working and can't think of what else to check there's no leak, temp gauge doesn't rise, fuse isn't blown what else could it be? It was working perfectly fine back in October of this year after using Blue Devil Radiator Flush 3 in 1 to clean it out and used it again this evening however it did blow heat for 10 seconds 4 times then went back to blowing cold air while the cleaner was in there.
Are you sure it's not a problem with your blend door not letting hot air through?
I'll check
If both the heater hoses are hot, then the problem is with the temperature control as Chuck says, and you'll probably have to disassemble the dash.
I'll check
Chock and Joe are on the right track. It sounds like the heater control valve may be clogged up.
Oh dear....