Do I need new thermostat or heat pump interior unit?

How can I tell if I need to replace honeywell thermostat or the heat pump interior unit? No circuit breakers tripped [tried and reset them all], no lights, no noise, no 'startup', no nothing. System [trane and honeywell thermostat] was installed 1990, I am original owner. Exterior unit replaced about two years ago. Thoroughly cleaned interior unit when it 'clogged up' two months ago with vacuum, brushes, weak disinfectant, and thorough flush of 'aquarium pump' and tygon tubing. I think I put everything back together correctly! Need help; starting to get into 30s at night. Thanks, Sammie. 20081021, 1403 est.
.. wolfgangk626..

Follow the thermostat wiring diagram and jump it out of the circuit, That way you will know if the thermostat is causing the problem.

Follow the thermostat wiring diagram and jump it out of the circuit, That way you will know if the thermostat is causing the problem.

Um, thanks. Where would I find the diagram [don't see it inside cover I popped off], and what on earth is 'jump it out of the circuit? I'm a scientist, not an electrician! Does that mean 'trip the inside -- and outside for good measure -- heat pump switches' ? I DID tip the thingie to freeze to death setting, and nothing happened at thermostat. Please make it simple for me to follow directions. T here are also two fat circuit breakers on the interior unit; a 30 and a 60. The ones in the box I do not trust, because labels were switched and several years ago, a visiting electrician tripped the wrong heat pump one at the circuit box ad I had an eight hundred electric bill in February. Thanks in advance for your SIMPLE please, help.
Sammie.

Usually the diagram is located on the inside of the blower motor door panel.

Jumping it out means to bypass the thermostat wiring. You can do this at the thermostat or at the inside unit low voltage wiring terminals.

OR you can just push in the contactor in the outside unit in and see if the outside unit starts and runs for a few seconds. NOTE use a insulated device to push in the contactor/starter since live 240 volts is present on the main terminals.

If you set the thermostat to emergency heat or set it all the way up and nothing happened then you should check for 24 volts at the transformer inside the inside unit.

Once you find the wiring diagram that might help you to figure out some things BUT since you are not knowledgeable on electric it might be safer for you to call for ON SITE service so nothing gets screwed up in the testing process.

I am all for the do it yourselfer but sometimes it is better to let a professional come to your house. Yes they can be expensive but so can burning up something by making a mistake while you are working on the unit.

Thank you for your gracious reply. If I had nothing else to do, I'd go take a community college course on the topic, but your wisdom prevails. Called the heat-pump folks tonite; it's easier for me to find some cash, then to come back to life, or re-build the house.

Thanks so much; feel free to contact me for any questions on growing roses, German Shepherd Dogs or police dog training, pharmaceuticals or vaccines. I'll crawl back under my crate now. No more heatpump exploring for me! I owe you some favor in the future.
Thanks again, Sammie.