visor_down
Member
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- 410
- Location
- UK
Hi all
Have problem with the interior heater on fiesta, basically will not blow hot air at idle, only when the engine is held at sustained revs (ie when moving)
They are well known for the circuit board on the rear of the heater control knob going or the heater control valve (HCV) getting stuck, however both seem to be working on this one
The heater circuit provides a pulsed earth which is varied depending on the setting of the control knob and allows more or less coolant to flow through the matrix.
Have established the following:
• The control board is providing a pulsed signal and you can feel the solenoid working in the HCV.
• Replaced thermostat
• Replaced coolant, flushed the block, matrix and rad with thermostat removed. Both rad and matrix flow readily. The header tank lid was left off, engine brought up to fan cut in temp and all hoses squeezed to bleed air (there are no bleed screws)
I can only think that there is a restriction in the system somewhere (next port of call was the oil cooler fitted to the rear of the block), my thinking being that the water pump can only provide enough pressure to feed through the HCV (at top of system level with header) and matrix when the engine is revved or that the water pump itself is faulty or inefficient to allow sufficient flow of coolant at idle.
That or the HCV is working, but not opening fully and causing a restriction, the pipes on the matrix side of the valve do get hot though. Was considering bypassing the HCV and oil cooler in turn to see if that resolves it (for diagnosis not on a permanent basis obliviously)
Anyone had similar or have any ideas?
Don't really want to drain the coolant yet again without a good list of things to check
Have problem with the interior heater on fiesta, basically will not blow hot air at idle, only when the engine is held at sustained revs (ie when moving)
They are well known for the circuit board on the rear of the heater control knob going or the heater control valve (HCV) getting stuck, however both seem to be working on this one
The heater circuit provides a pulsed earth which is varied depending on the setting of the control knob and allows more or less coolant to flow through the matrix.
Have established the following:
• The control board is providing a pulsed signal and you can feel the solenoid working in the HCV.
• Replaced thermostat
• Replaced coolant, flushed the block, matrix and rad with thermostat removed. Both rad and matrix flow readily. The header tank lid was left off, engine brought up to fan cut in temp and all hoses squeezed to bleed air (there are no bleed screws)
I can only think that there is a restriction in the system somewhere (next port of call was the oil cooler fitted to the rear of the block), my thinking being that the water pump can only provide enough pressure to feed through the HCV (at top of system level with header) and matrix when the engine is revved or that the water pump itself is faulty or inefficient to allow sufficient flow of coolant at idle.
That or the HCV is working, but not opening fully and causing a restriction, the pipes on the matrix side of the valve do get hot though. Was considering bypassing the HCV and oil cooler in turn to see if that resolves it (for diagnosis not on a permanent basis obliviously)
Anyone had similar or have any ideas?
Don't really want to drain the coolant yet again without a good list of things to check
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