Heater not working - Honda Prelude Forum

Dallicis · 11-16-2004, 04:13 PM

Well, i havent had a heater for over a year now and its getting cold again. I figured I would try and see what it is. I checked all the cables already and everything is fully functional there. Today, i ran out of daylight, but I took off the heater hoses that lead into the firewall making sure they werent blocked and checked the functionality of the flap itself... All checked out fine... Now, heres my problem.. There is no flow, so it has to be blocked somewhere. The heater hose gets hot where it normally would if the heater was off, but doesnt get hot along the line. The return hose doesnt get hot either.. I am thinking its most likely blocked off in the cabin of the car. Sometime tomorrow or thursday i am going to take off the return hose and turn the heat on to see if I get flow, and thatll tell me its not blocked inside the cabin, but I dont think itll do me any good... How can I unblock it inside the cabin? Am I going to have to remove the heater matrix or what? Anyone?

dohcpower v2.0 · 11-16-2004, 04:27 PM

sometimes i hear if you reverse the flow.. ie swap the hoses on the heater core, it might breake up the blockage...

i've never personally tried it, but i've heard of people doing it to break apart a blockage.

Lucke · 11-17-2004, 09:39 PM

well, i had to do a heater core bypass because my heater core rusted through. but it sounds like something might be blocking it, although i'm not sure how that would happen out of nowhere. that would mean that you would have some crap floating around in your coolant... once you get this all figured out, make sure you flush your radiator.

Dallicis · 11-20-2004, 11:58 AM

well, i got it fixed... I went to the auto parts store and bought a bottle of system cleaner.. Its supposed to break apart deposits.. I then disconnected the heater hoses form the engine and tried to blow in one end.. No good.. Definentley the heater core was blocked.. So, I sucked the antifreeze out.. Be careful if you do this. Then I poured some of the system cleaner in.. Let it sit for 30 minutes.. Got a water hose and tried to use extreme pressure to unclog the blockage.. Sure enough, it was messy, but it worked and some nasty build up spewed for about 4 minutes out of it.. Then, I put more cleaner in it and let it sit another 30 and repeated... Then I reassembled it all and added cleaner to the radiator and let it run... The heater works now, not great.. But I am sure its still partially blocked and maybe the cleaner will help it out.. It says drive it around 3-6 for best results... So, thats the game plan...