The chilliest heat in town

Hello! I have a 99 Ford Taurus I bought used over the hot summer after someone turned my poor little Escort into an ex-car in a bad accident. Didn’t think to check the heat in the new car at the time (I was more concerned about the a/c working!)

If I turn the heat on any setting other than low, it will be warm for a few seconds and then blow out cold air - not a/c level cold, but nothing warmer than outside the car. If I keep it on low, with virtually no blowing, it’s okay. I’m somewhere around the level of “broker than broke” these days, so I’m reluctant to take the car in and find out I’ll have to decide between groceries and fixing a car problem. Any guesses as to what this odd situation might be? (I’ll hang in with the low-level warmth this winter, but this still puzzles me.)


Is the coolant level full? What does the coolant look like, green, yellow, brown or black? Your cooling system also provides heat to the cabin. Check both heater hoses when you have the car warmed up and the blower on high. Are both heater hoses hot? If not, the heater core is probably clogged up. You might be able to flush it out. If it is clogged, it is an indication of poor maintainance so you should be looking for more problems in the cooling system.

The engine thermostat might be stuck open. This would cause the coolant to constantly circulate and probably the temp. of the coolant is somewhere around 150-160 deg.

I,am not sure but check the hoes going to firewall into heater. Is there a vacuum or wire controled valve in line. it might be open all the way. and with fan on full your are cooling the fluid in heater core to fast. your put some card board in front rad and run the temp up in rad
and try high speed if there is no control valve in line. and if this works then go to thermostat. you can take off both lines leave them connected at fire wall and use low pressure hose and flush in both directions to check for clogs. you know if any one put rad leak in to stop aleak it could have cloged the small tubes in heater core. your problem is not hard to find.

Unfortunately the design of the Taurus heating system leaves a lot to be desired. Find where the hoses go in and out of the firewall which is where they go into the heater. As stated above, they should both be hot, one just a little less than the other. If you have access to an infrared laser thermometer, use it for a check. Otherwise you need to be especially careful not to burn the back of your hand on the rear exhaust maniforld or its baffeling as you touch the hoses on the thoroughly warmed up car.

If both hoses are hot, then you have a flapper door issue. The flapper doors on your Taurus are electrically operated. There is a small white plastic box mounted to the INSIDE of the firewall, just to the right of center. It has a plug in with several wires going into it. There is a 1/4" square hole in the plastic box that you should be able to see rotate as you run the control from hot to cold. It only moves about a quarter turn, so watch closly. If there is no movement, check that the plug is plugged in. If it is, then the box is probably your problem. It comes off with four 8MM bolts, most easily accessible thru the oval radio/HVAC control hole after the control is removed. Use a long extension (or two) with a swivel at the end. A new one is under $100 from Ford, much cheaper at a salvage yard.

If your hoses are cold, you have the proper amount of coolant in the system, and the coolant temperature is up where it should be, THEN you have a plugged heater core. FIRST try pushing the clog through the core with Garden hose. You can clamp off both the inlet and outlet hoses with two of those four inch wide flat panel bending vice grips. If you don’t you’ll lose most of your coolant. @ $12 a gallon, you don’t want to waste it. Be sure to clamp the hoses off before you pull them from the heater core. The flow in and out of the heater core should be pretty much the same as it is with just the hose, in other words, no restriction. If it is restricted, you have two options, a new heater core @ $600 to $800, or flushing it out with some CLR. It’s a product used to dissolve Calcium Lime and Rust, available at any Wal*Mart.

Configure two funnels with two 18" hoses that will attach to the heater core. It helps if they have 90 degree bends near their ends. Clamps are pretty much optional as there is no pressure on the system. Pour CLR into the lower hose to the point where you see it come up into the other funnel. That way you know the heater core is full. Leave the 50/50 mixed CLR in there core for 30 seconds or so. A HUGE drain pan is nice for catching the outflow, as it will stain concrete. I usually do it twice to get all the crud out, with a garden hose flush between CLR treatments and at the end. If it eats a hole in your heater core, it was probably due for replacement anyway. So far, I haven’t had one leak yet, and I’ve done several. I’ll probably do another one tomorrow.