Please play nicely. No one wants to listen/read a keyboard warriors rants....
Bad alternators seem to be able to manifest themselves in many ways but would high revving at idle as opposed to low revs /cutting out (which seems more the norm for an alternator issue) be a sign when coupled with other electrical issues?
It depends on the ECU. I don't know if your ECU does it, but, ECU's do monitor battery voltage. They also control idle speed (via the idle air control valve). Normally idle speed is mostly dependent on engine temperature - so on a cold engine it'll be 1000+ rpm, and then as the engine warms up it slowly reduced to 600RPM ish. However, it's entirely possible that your ECU also has a mode where it increases RPM if it detects low battery voltage, in order to increase the charging current generated by the alternator. If it's actually the alternator that's faulty, then battery voltage may never increase, so you get permanently high idle speed.
ECU's also often increase idle RPM when A/C is enabled - to compensate for the extra load the A/C compressor puts on the engine.
I don't know if the Ashtray ECU does any of these things, but it is at least possible, and could explain what was going on.
Astra still driving fine with ac on and absolutely no issues after nearly a week. Eden maintain that it could not be that as the engine was revving erratically when they had it. They gave me so much bullshit as to why they could not diagnose. Independent Auto Electrician was adamant from get go that it was the alternator.It appears to be fixed, Phil. Personally, I wouldn't worry about the whys and wherefores.
Bad alternators seem to be able to manifest themselves in many ways but would high revving at idle as opposed to low revs /cutting out (which seems more the norm for an alternator issue) be a sign when coupled with other electrical issues?
Eden are stumped - it has now been referred to Vauxhall Technical Assistance HQI take it it's an astra K, Phil?
Sorry, just seen it's a J.
