Heater controls mk5 Fiesta - pastyman
I have a Mk5 Fiesta on a W plate, when the car is cold the heater is cold, driving along the heater get warm then warmer, but all this is with the control turned to cold. If i want heat and turn the dial to fully hot, i gets hot, but when i turn it back to cold, it stays hot, even after a few miles.
I understand that the control itself may be faulty or the valve against the bulkhead behind the scuttle might not be closing properly, i think the valve has a motor of sorts to close it.
Has anyone got any ideas or if this is a common thing on the Mk5 Fiesta or an easy repairs. Is there any way i can test the control and the valve seperately ?.

Pastyman..
Heater controls mk5 Fiesta - king arthur
That's interesting - I've got a mk4 one that's doing exactly the same right now. If anyone knows the answer I'd be keen to hear it too!
Heater controls mk5 Fiesta - Dave N
This is very common. The control knob sends pulses to the heater valve. Lots of pulses let more hot water thro' to the heater, less, and less heat. There is a TSB for a new control ecu, and valve if necessary, so speak to your ford dealer and they will fix it for you, and come to the party with a part payent.
Heater controls mk5 Fiesta - elekie&a/c doctor
Assuming that the cooling system is up to spec,adequate water & no overheating,then the most common fault is the heater control valve.It is situated in bulkhead area between wipers &engine bay .Part costs about £35 & about half-hour to fit.
Heater controls mk5 Fiesta - pastyman
System is up to spec, coolant level and concentration ok, no overheating, no apparent change on temperature gauge. This control valve, does it use the motor to open and close the valve pretty much like the changeover valve in a central heating system?

Pastyman..
Heater controls mk5 Fiesta - Dave N
It's like a solenoid valve, that gets a 'shot' of electricity that momentarily opens the valve, letting hot water through. Depending where the hot/cold knob is set, depends how rapidly it gets its 'shots' of power.

It's on TSB 123/1997, entitled 'Heater temp control inoperative'Summary

Should a customer report that the heater always blows either hot or cold air, the cause may be either a damaged wiring harness, damaged electrical connectors, an inoperative heater control valve or an inoperative heater control panel. This concern can be resolved by renewing the affected component(s). Fiesta variants also require fitment of a heater control valve cover.

This bulletin supersedes pages 1, 2, 11 12 of TSB 123/1997 dated 05.06.1997 and features a revision to the Service Instruction. Please destroy the corresponding pages of the previous edition of this bulletin.

Heater controls mk5 Fiesta - pastyman
Thanks for your help chaps. I have bought a new coolant control valve, looks easy enough to fit, my Ford dealer says the failure of the valve is a common fault on a Fiesta.

Pastyman...
Heater controls mk5 Fiesta - king arthur
You bought a new one? I'm gonna go nick one from a scrappy!
Heater controls mk5 Fiesta - pastyman
Yo King Arfur, majesty dude,

Me car is only 3 years old, i dont want secondhand toot on my set of wheels. Besides that, theres a chance that the one out the scrappy might be duff as well, its seems a bit of messing about only to find you've got to do it all again.

Pastyman..
 

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