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Help! Fiesta Mk4 Heater Has Stopped Working Completely.

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I've just signed up to see whether anyone can help with a problem I'm having with my heater.

Basically, my heater started playing up a few weeks back by only working on setting 4. Within the last couple of days, it has given up the ghost completely.

I'm familiar with the usual reason for this (the resistor), as I had the same problem about 3 years ago and resolved it by replacing the resistor with one from a breaker's yard. This served me well until recently, with all four settings working fine.

Anyway, when it started only working on setting 4, I rather stupidly ignored it.. Partially because I was lazy and could still get some form of heat out of the device and also because I work in a different town to where the breaker's yard is, (so found it difficult to get there after work before they closed). Anyway, the heater forced the issue by failing completely on Sunday morning, (yep, the day when we had a severe frost). It had been working on setting 4 the previous evening as I travelled back from watching the boxing round a mate's house. It was cold then, so I ran it on '4' for the full 15 minute journey home. Anyway, I tried using it the following morning (about 8 hours later), only to find it had packed up completely.

Thinking it was a resistor failure again, I managed to pick up a 2nd hand resistor from the breaker's yard and fitted it on Monday night, hoping that would do the job. It didn't.

On closer inspection, I noticed that the block that houses the four wires and plugs into the resistor appears to have suffered some heat damage. The bottom right hand area looked to be partially melted and that particular wire had come loose. As a result of this, I made another visit to the scrap yard and bought a 2nd hand block with about an inch and a half of wiring installed.

I've just spent the evening removing the old semi-melted block from the car's wiring, have tidied up and trimmed the existing wires and crimped them to the 'new' wires and block. I then tried the heater again. Still no joy. No hot or cold air at all and no indication that my attempted repair has made any difference whatsoever. I tried swapping the old and 'new' resistors, just in case, and still nothing.

As such, I'm stumped. My knowledge is very very limited and although I've googled the problem, all the answers seem to suggest that I replace the resistor, (which I've already done).

The only thing I can think of is that the colour of the wires on the new block are slightly different to the old one. The old one had white, yellow, blue and black; the new one white, yellow blue and orange. Rather than connect colour to colour as far as was possible, I took a note of the position of the old wires in the old block and matched their positions when linking the wiring, (i.e. the wire installed on the bottom left on the new block has been crimped to the wire that was installed to the bottom left of the old block, etc). Could this be the reason why the heater still refuses to work, (should I have matched colours instead), or is it something else (and potentially more costly)?

If anyone has any ideas, I'd be very grateful if they could let me know. I'm very worried about the next frosty day and the fact that I'll have no way to heat the vehicle (and more importantly, no way to stop the screen and windows misting up once I'm moving).



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i know this may be a stupid question to ask but have you checked the fuse and relay, are you getting power to the resistor or switch?

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Hi. Thanks for replying.

Not a daft question; I've checked the fuse, which is ok, but not the relay. How can I check this and how will I know if it is ok or not ?



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If a relay is working you will hear a click as it engages/disengages.

No click equals duff relay or no power to it.

I'd replace the relay first and go from there.

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Sorry but i may be asking a silly question as I have a mk4 1996 fiesta, do you get any heat when driving when the engine is hot and the temp turned up to max? (Close passanger side vent to force more out of driver side vents) You should feel it on your hands with windows closed if you set it to come from the vents on the dash.

Also have you tried the heaters on all 3 settings? Footwell, dash and front window?

I have noticed that even with the heater fan set to 0 and heat set to max it will come through enough to feel it when driving. Does it blow air when you turn it on all settings like 1, 2, 3, 4? If you can feel heat coming through the vents wile driving turn it down to, cold does it go back to normal temp?

On settig 4 it should cook you alive with heat set to max. If its trying to spew out air and cant maybe check for blockages? Iv not had the problem but it will be good to know what the problem is it you manage to resolve it.

Best of luck.

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