Ford Focus 2000 - Heater Problems

Possibly a bad valve that lets the hot coolant flow into the heater core. Bad heater core may have a blockage. Hose crimped feeding it. Does the blower work? Is the engine getting up to the proper temperature?

I seem to recall having a clogged heater core once.

That happens often when you need to top up say once a week, never actually fixing the problem and you live in a hard water area.........

Very possibly your problem is being caused by the cabin air filter which most people don't even know their vehicle has and becomes clogged and will not allow the heater or a/c to provide enough air flow to transfer the heat or cooling into the cabin. Hope it helps and good luck.

Air filter has also been replaced. Whenever I accelerate to 55mph there will be an heat just enough to defrost my windsheld, as soon as I decelerate below 30mph it would become a cool air.

Your speed-dependent results may point to another possibility. Some cars use vacuum solenoids to control various aspects of the HVAC system (Ford in the US DEFINITELY used to do so, routinely). If there is any vacuum leak, especially if near the solenoid, you may only be able to position a valve or an air door properly when you have sufficient vacuum and air flow in the manifold. I've seen the problem on late '80s VWs; on a Jetta, I made up a wire clip that held the solenoid in the door-closed position and would snap it in place in cold weather, until I had time and a workplace to install its replacement. If this is the issue, you MIGHT be able to hear a change, if you deliberately turn off the radio and drive on a road with little tire noise. If you have any other problems, such as starting issues, fuel mileage, etc. that might be affected by a vacuum leak, check this out.

Good point.

The actions of the heater controls can easily be checked with a running engine, but the car stopped. If the vacuum is good ( engine running with throttle closed eg tickover, will give the best vacuum....), the valves will open and close with a discernible sound.

It sounds as though your thermostat is stuck open and your motor is overcooled. This is my primary suspect.

What does the engine temperature thermometer say. If not marked, it needs to be in the middle of the scale.....not anywhere else, when running.....

Also possibly you do not have enough antifreeze and the rad is freezing up, though usually this gets the motor boiling!! Be careful. The pump impeller blades can get sheared off if the water is freezing....then no flow of water, a hot motor is often the resul.

Maybe the water in the heater is also frozen and the warm water just simply cannot get through!! Get a garage to check the antifreeze strength.

Another possibility is an air lock in the heater pipes. You say you changed the radiator fluid, but was the system bled at all the nipples? And a second time after a drive?

Water will flow through the lock when pushed hard, but not enough to disperse the air fully, and further bubbles will accumulate.

Heating systems are designed to have a high point around the bulkhead, the aim being to reduce the flow into the cabin should the matrix leak. Have you any problems with odour or greasy glass? - often the sign of a small leak in the matrix.

Some cars need to be "Jacked" up at the front when filling......for that very reason.

Other than heating problem, everything is fine. I took my car to the shop, the guy disassemble the pipe and clean it before he refilled the fluid. He sugested that I need to change the water pump and I don't know if this is true, since he already charged me 95$ for what he had done.