Fiesta heater

[MickyP10]

My daughter's got a Y-reg Flight and the heater's permanently hot, so I'm guessing the cable is broken or become detchade. Anyone taken the middle bit of dashboard off or can you get to it by sitting upside down wityh a torch?

 

[MrTinker]

It will be the control valve which is located under the bonnet in the centre below the windscreen, it will have 4 hoses on it and a leckie plug, these get full of crud and jam in one position, take it off and clean it out, should do the trick.

 

[MickyP10]

Ta. Had heard about that and that the Fiesta doesn't have a cable! Have measured the voltage at control valve plug and it's nowhere near 12 volts, so don't know if it's supposed to be stepped down or whether the dashboard bit with the knob is faulty. Don't want to throw money at the car so was thinking of sticking a central heating isolating valve near the heater valve (£2!), then turn it on or off for winter. What do you think?

 

[jetex]

Be careful removing the pipes off the valve, as the pipe stubs get very brittle and will snap off. A new valve is around £40.

 

[MickyP10]

Was thinking of cutting the hose before it gets to the valve. The issue I have is I'm not sure what voltage should get to the plug on the valve - because it seems to vary to between two and five volts. All of which may mean the valve is fine but the dashboard bit is duff. I'm told they're £80!

 

[MrTinker]

I've done loads of these and usualy it's because they are blocked up, i've had a fair few that where faulty mind, but it's well worth cleaning it out first, also i should have said be carefull removing the pipes, as jetex said.
Don't cut the hoses! twist them where the hose clips where when you have moved the clips down the hose.

 

[MickyP10]

Okay, maybe I have a look at it first, and if it isn't obviously crudded up, I'll try my trick. Would it be more likely to stick shut than open? Ie be cold all the time rather than hot - or doesn't it work that way?

 

[MrTinker]

I've had them do both. It's a bypass valve though so when the valve is open the heater is cold and when it is shut it's on hot.

 

[MickyP10]

I thought I'd try leaving the plug disconnected and maybe it would get colder. Seemed to get hotter, though, unless my imagination! Anyways, I'll have a look tomorrow.

Thanks!

 

[MrTinker]

With the plug disconected it is on hot, so that makes sence.

 

[MickyP10]

Post mortem. Couldn't find owt wrong with valve but was still worried about low voltage feed from dash, so thinking I'm probably going to end up with replacing the dash and valve, at, hell £130-plus. So I added my isolating valve, which works quite well. Come winter time, I'll turn it 90 degrees and allow hot water into the heater matrix.

 

[mfarrow]

I believe the output from the dash is pulsed, i.e. it's peak 12V but the time 'on' varies with the required temperature. A cheap multimeter will just report the peak, so you'll never see any variation. You'll need an oscilloscope to check it properly.