How can I tell if heat exchanger on my gas furnace is broken?

I have a high efficency gas furnace that runs good. But after it shuts off a little water leaks from underneath it. The pcv vent, drain and pump are fine. Does this mean my heat exchanger is broken or could there be a loose hose connection inside the furnace?

most likely you have a loose hose. pop off the cover and take a look. there will be a drain hose from the induced draft blower and one from the secondary heat exchanger. both of these hoses will hook to a trap of some sort.. on rheem ruud and weather king itll be a round black box.. on trane and most others the trap will be rectangular and white.....what ever the brand, the trap will be hooked into a drain, or condensate removal pump.

if you are in serious doubt, get a carbon monoxide detector. there cheap, and they could save your life.

if you call a service man, dont act panicky.....a good service man can find a leak in a brand new unit....no lie...they all leak a little, but they suck in fresh air rather than blow out fumes unless there is a serious hole or crack.

rheem imperial drum units were a peice of junk and should be deep sixed as a matter of habit.

hope this helps,
Possum,hvac guy

LIGHT A MATCH AND WAVE IT AROUND THE FURNACE

If your heat exchanger was leaking, you would probably see some vapor around it while it was running and a CO detector would give an alarm if set next to it. But take off the cover plate, and find where the condensate hose is coming off the heat exchanger, and look for a leak. I think your second guess is the right one...a loose hose inside the furnace.

You should have your furnace serviced by a factory authorized professional. A seasonal service is not that expensive and they will make sure that your system is operating properly. Be sure to let the technician know about your concerns. The newer high efficiency models are far too complex to fix with no training. I typically do all of my own work, but that is one of the few areas that needs professional know how.