Fiesta Heater Not Working

bheart65

Hi Folks,

My cousin owns a 2002 Mk4/5 Fiesta van with the 1.8 turbo diesel engine. Recently, the heater has stopped blowing out hot air, he said it was blowing out only hot air before it failed. The fan is still working in all positions - 1-4 but only cold air is blowing out. He's had it looked at by 4 mechanics plus sundry outsiders. Here's a list of what's done so far:-

1. New heater control valve, power checked to connector and is working correctly. Both hoses behind new valve heat up after a while so water is circulating.
2. Heater Matrix taken out and flushed with water flowing freely
3. New Thermostat
4. Air Bled from system

Still no hot air blowing out. We are at a loss as to what else might be the problem. I was wondering:
(a) If the heater resistor might have any bearing on it but I think that only has affects blower speeds ie. 1-4 and they're all working.
(b) Would the coolant temperature sensor have any bearing on whether the heater would blow out hot air or not, it's about all we can think of left to replace on the coolant side of things.
(c) Is there any flaps etc. at the bottom of the box that the heater matrix sits into that might be broken and stuck closed, not allowing the hot air to come through into the car.
(d) Would a faulty ecu be the cause.
(e) Would a new water pump help rectify it?

If anyone thinks the coolant temperature sensor could be a cause and needs replacing could someone please post a pic of where it is in the engine bay as he's already spent over €300 on parts and labour and can't afford much more.

We're all scratching our heads and can't come up with any solutions. Any help would be greatly appreciated.

Thanks for looking.
Tom.

corktina

I have no experience of diesel Fiestas but if it was petrol two things common to go wrong are the switch panel on the dash and the heater control valve on the bulkhead in the engine compartment.

bheart65

Hi Corktina,

Appreciate your time. We've already replaced the heater control valve and on your advice have swapped out the switch panel with another fiesta that is definitely working but still no joy. Another possibility might be the heater door actuator might be worn and need replacing. Will try that next.
Thanks again.

mickdw

The control valve at the bulkhead is such a common issue that if a breaker part was used, it would be quite likely that the replacement was also faulty.
Seeing what has been checked, it can only surely be the control unit or the valve as corktina says

bluezulu49

Hi Guys,
We have two 2000 vintage Fiesta Zetecs in our household and have had trouble with the heater control valve in both. (They stick open or shut.)

Initially I solved the problem by buying new valves on ebay but a weekend failure led me to take out the valve, open the solenoid switch and clean it.

Two screws hold on the silver solenoid cover. If you undo them there is a piston like object inside which tends to get gummed up. I clean this up with 400 grade wet and dry sandpaper and also the bore in which it travels. I then grease both items and when assembled they work again. I have done this so often that from inception to completion now takes me 20 minutes.

Electrical operation of the switch can be tested while the valve is out of the car.

Hope this helps.

Bluezulu49

bheart65

Thanks guys,

The replacement heater control valve was a brand new Ford replacement. When it didn't make any difference we thought it might have been a dud, so we replaced it with one out of another fiesta whose heater was working and still no joy. So the new hcv was put back in, besides we're getting hot water in both pipes on the matrix side of the valve so water is circulating. I'm starting to think the flap motor on the heater box may be the issue as there seems to be heat getting as far as the matrix but not into the car. I'm presuming the temperature flap is stuck in the cold position, so will check that out over the weekend when I have a bit of light.

Thanks again for all your help.

corktina

i'd recheck the dash panel. I took the back off mine and the knob was not located in the square properly meaning it was not actuating the electrical gubbins that opens the heater up