I've got a 91' Accord and the heater stopped working but the fan is still good. No sweet smell of anti-freeze inside the passenger compartment or leaks on the floor so I eliminated the heater core as being the problem. Changed the thermostat thinking it was stuck open, bled the cooling system and still no heat.
Does anybody have an idea what I should check next? I live in Canada and ol' man winter is just around the corner, HELP!
Is your new thermostat OEM or aftermarket?
How about a block in the heater core, or one of the lines running to it? A chunk of rust or other debris could have come loose inside the radiator and made its way to the core.
Try disconnecting the two heater lines *from the block*, force water into one of them (making sure the heat control is set to full hot), and see if it comes out the other. Then force water into the other hose as well, so if something is clogging it, it may be forced out.
The coolant valve in the heater line under the hood near the firewall may not even be opening. Those things get stiff in almost every car made, probably because they are mostly plastic. A squirt of silicone on the rotary shaft couldn't hurt, but it is fairly likely the operating mechanism is out of whack now. It doesn't even get mentioned in Haynes, but the air mixer assembly is at the very bottom of the center console and is easily accessible from the passenger side by pulling the carpet aside and unfastening the duct that covers it... a couple of screws, IIRC. Both the operation and adjustment (by loosening the housing clamps and refastening them when the cable is in the right position) are fairly obvious if you look at it and twist the temperature knob. At that location you can also unfasten the actuator cable that goes to the valve and operate it by hand to check the resistance of the cable/valve pair. If the temperature control knob is broken, it is available from Honda for something around $10 CDN. Changing the valve is a more serious thing and demands you be very careful to avoid slashing your hands and wrists. Don't ask me how I know :-(
Mike
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