following on from this post -
https://www.scoobynet.com/other-marq...g-problem.html

i've had the cold air blowing problem, the heater control valve has been replaced, the thermostat has been checked and working fine, the coolant system has been drained and replaced but the cold air problem persists....

could anybody suggest what the cause could be? or a fiesta based site that could provide more info?

tia
max

 

either its not been done properly and you have a nasty air lock or the heater matrix is blocked

 

Did you check the power supply coming from the heater control (on the dash) to the valve? AFAIK it should be a pulsed 12v. If you're getting nothing then it could be the heater control on the dash. If it is, you'll be wanting one of Fleabay like this :-

eBay.co.uk: 1996 Ford Fiesta Mk4 Heater Control Unit Panel (item 300044389204 end time 08-Nov-06 12:34:15 GMT)

because they're about £120 new apparently

 

cheers for the replies guys

i have been thinking its a power supply prob, ie the heater control on the dash, but would it be the cold to hot blower?, as the 1,2,3,4 heater controls still works!

does anybody know if the whole panel needs to come out or can i just pull the cold to hot controler out and check somehow?

gaz-cole, where/what is the heater matrix?

 

The electro wizardry is on the back of the panel I posted up there ^ small circuit board. (the fan switch is seperate, as is the direction switch which still sensibly runs off cable)

Unless, you are watching that panel ^ on ebay, someone is about to get a £4.99 bargain in 13 mins

 

the heater matrix is the small radiator on back of your dash board thats where the warm air comes from on the inside of your car and if its blocked at all you wont get any water flow trough the heater matrix

 

Common problem on Fiestas is the HCV.

Try fitting an older model HCV if possible.

 

now i understand! doh, didnt bid on that item as it was for the mark 4 and i've got a mark 5, but if all i need is circuit board, i'll look out for the next one

do you know if its a plug in job, or am i going to have to get the soldering iron out?

thanks again

 

It's a 2 minute swap (plug in) but check whether you have a pulsed 12v at the valve on the bulkhead, because if you do, it aint broke

 

have got a 12v pulse at the HVC!

nexts tep of diagnosis, looks like its going to be the heater matrix, not much else left to check...

gaz-cole, any idea how to access this? is it a remove dash job?

as a side note, the heater now provides its own 'natural' heat once the car is warmed up and moving, end up stationery and it goes back to cold... would this be more signs of the heater matrix not working?

thanks

 

sounds like bad flow to me. You've replaced the valve and the heater controls are okay. So as long as you have hot pipes at the valve, it's cabin side. Try taking the valve off again and using a hose-pipe down the hose into the car. use it in the reverse direction to normal flow and it *may* clear any blockage

 

cheers stainy, can always try that aswell