I've recently had a problem with the ventilation and Air Conditioning (AC) controls failing, with none of the lights below any of the button selected lighting up. I replaced the 7.5A fan relay fuse in the bottom right of the fuse box below the dashboard, and all was well once more, but it failed again due to the fuse blowing after about 2-3 minutes of driving with the AC on. I tried another fuse, and as soon as I turned on AC, the new fuse blew. I think I could hear a click sound when it failed, presumably from a relay.
When it has failed, the fan still blows air, and I can adjust its speed and temperature with the two dials. AC wont work though, and the buttons will not adjust where the air will be blown. It stays permanently on the air direction that it was set on when it last failed. Losing AC is a serious problem for clearing the windscreen in winter, so am keen to get it fixed soon. But I fear that with quite a complex system, it could be time consuming for a garage to diagnose, so am hoping some of you can help.
Though it's probably unrelated, I do have a problem either with the wiring or more likely the ECU, which was repaired 3-4 years ago following burst capacitors, as I've recently been getting error codes for the TDC and no.1 cylinder sensors, yet have had both replaced recently to clear the problem, and I still get engine warning lights. Can't remember which was the latest error between the two. The car occasionally stalls on me, and occasionally stutters or just loses its spark and drops the revs down to zero. But it's not that bad, and runs fine most of the time, albeit with the engine warning light often coming on. Will probably just get a new ECU soon, but with a little beginning of rust underneath too, I fear this additional ventilation issue is making me consider my beloved's future a bit. If I can solve that, I can deal with the others I suspect. Though one thing I fear is buying a new ECU and finding that it was the wiring at fault, which would leave me with a brand new ECU needing selling, and no hope of fixing the wiring. But I'd hope I could find a buyer of the new ECU for a decent price if it came to that, particularly as I understand that the latest replacement ECUs are built with a lot more durability than the original.
Anyway, back to the ventilation issue. Firstly, it would be handy if anyone can advise whether there's any way the ECU is causing the ventilation issue, as its circuitry does interact with the AC. If I can solve both the AC *and* engine problems with a new ECU, then that would be great.
I've attached the translated wiring diagrams, with the most applicable being on page 6. I've also attached the heating system workshop manual which has a wiring diagram on page 15-6 which also shows the switches for the controls. I'm a bit confused, as the two diagrams don't really appear to be consistent, but maybe they show the same thing but from different perspectives. You can see the 7.5A fan relay fuse on both, and the AC system, but I can't quite figure it out.
Note that I wonder whether the AC system needs its gas or fluid replaced or topped up, as apart from a new belt, it hasn't had any maintenance for a decade or maybe two. Could this be the cause?
Reply With Quote
Originally Posted by Bruce
