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Originally Posted by gsxr
1) Sounds to me like your new VFC is working as intended. Temps up to 100C are normal. Temps above 100C are usually not (unless ambients are very high and/or there's extended full load.)
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the vfc will not engage until very close to 100C. the problem is this, the darn thing once engaged will not disengage properly. it stays on so long, that the thermostat closes up completely in an attempt to maintain the engine temp around 82C. once the vfc finally disengages, the temp creeps back up, and the cycle starts anew. when you stop, the temp spikes up rather alarmingly due to the fact that the thermostat is closed! i know the thermo works because i watch the temp gauge like a hawk, and can see it trying to compensate for the disengagement problem with the vfc.
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Originally Posted by gsxr
2) The VFC won't engage properly if the radiator has a 'cool' spot ahead of the fan. This can be very hard to figure out and more than one good clutch has been replaced when the radiator was the real problem. Also need to make sure the condenser fins are clean in front of the fan area to allow proper airflow.
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it could certainly be the radiator, i have no way of knowing without a laser temp gauge or something. the condenser, however, i replaced at the same time as the vfc and i cleaned all the crud out from the fins of the radiator and flushed the system and refilled with the proper coolant/water ratio, etc.
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Originally Posted by gsxr
3) The new/replacement VFC for the 603 is actually a 606 clutch with plastic fan. It's my opinion that this newer clutch is designed to engage at a higher temperature to improve fuel economy by raising engine temps to the 90-100C range, instead of the previous 85-90C range that most people expect. The FSM details exact temps for operation of the old clutch but is annoyingly silent on the details of the 606 clutch.
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if it would stay between 90-100C i would not worry about it, but now it goes to 105C sometimes, then back to 82C, then back up to 100-105C as the thermo tries to compensate for the vfc engagement problem.
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Originally Posted by gsxr
4) Aftermarket electric fans have a bad rap because they *usually* don't pull enough CFM to properly cool the car. And trying to get one large enough to fit is often a problem. Then there's the issue of the alternator upgrade and required electrical cable size increases, battery terminal modifications, etc - it's a lot of work. And for what? Don't forget they are usually a LOT noisier than the stock VFC setup. Now, factory electric fans are a TOTALLY different discussion. Mercedes can engineer an OE setup with the proper electrical system, CFM, and noise properties. But trying to retrofit this on an older MB is usually a waste of time and money - IMO, anyway. I have no plans to ever replace the VFC on my car. The one and only reason I'd ever consider it is if I were to go the SuperTurbo route and needed to relocate the radiator 2 inches back, and had to ditch the VFC to make room. (I don't plan to ever do this, btw... and it works in Finland because they're at roughly the same latitude as Alaska, if you get my drift.)
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my big issue with the vfc is not its operation (when working right), its the stupid little bimetallic strip that actuates it. if the strip does not reform itself upon cool down, the thing will not let the vfc disengage properly. hence, the vfc will come on erratically and go off erratically as the strip deflects with the heat.