Re: RPM drop - Saab 900 Bulletin Board - Saabnet.com
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Yes, it's due to the sudden electrical load but the reason it happens is because the fan is requiring excessive current to start, either because of inadequacies of the electrical system or because the motor is worn. The idle didn't sag when these cars were new!
I don't *think* the starting radiator fan idle sag is a result of the alternator's sudden increased load, but rather a loss of current in the system - weak spark, drop in fuel pressure, sudden wacko sensor feedback, etc. The inrush current of the aged motor has got be significant. Once the fan is started, it's not such a big deal and everything goes back to normal. The AIC is there to compensate for mechanical load, not an old electrical system.
The AC is a different scenario. The electrical draw of the AC clutch is actually not terribly significant, it's the mechanical load of the compressor on the engine that the AIC is compensating for, in the same way the AIC compensates for the extra load of the automatic transmission on '86+ c900s.
posted by 12.195.130...
Posts in this Thread:
- Clean radiator fans?, Tushy, Mon, 12 Jan 2015 11:24:57
- Thanks all, Tushy, Mon, 12 Jan 2015 12:51:31
- Re: Clean radiator fans?, Simon S, Mon, 12 Jan 2015 12:24:06
- Re: Clean radiator fans?, Justin VanAbrahams
, Mon, 12 Jan 2015 12:06:56- RPM drop, bill schultz
, Mon, 12 Jan 2015 14:12:02- Re: RPM drop, Justin VanAbrahams
, Mon, 12 Jan 2015 14:28:21 <-- Viewing This Message
- Re: Clean radiator fans?, Frankenstein900, Mon, 12 Jan 2015 11:53:47
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