OK.... Hustled up and installed the "D" fan in the cool of the morning. Sounds and operates just like the "C" version inside and out. On shore power, there's the turbo-like whistle outside. Heard only when standing by the coach door or rear wheel. That is good. That is very, very good!
IMPRESSION: There is no visual difference between the "C" and the "D" ... Samo-samo. There's no difference in the internal webbing, thickness of the hub or blade material .... or anything that I could see. The "D" does have a little smoother finish than the "C" version & no 'flash' that needed removal. So I didn't do any sanding or smoothing on the blades or hub. The "C" has a matt finish and is slightly grey/black. The "D" is a bit shinier and more black/black. The fit on the motor shaft looks to be the same as the old ones. The blade tips are still very, very close to the top of the electrical box. (So, another whack with a hammer just to be sure. Clearance is still about 3/16"......)
What is different is the weight. The "C" weighs 287 g (10.1 oz, for 'mericans) and the "D" weighs 300 g (10.6 oz). The "D" is 13 g (0.5 oz) heavier. It is the only difference that I could find. It's probably due to a more dense material used in the "D."
Interestingly, the "D" kit came with another 'hat' that is attached to the electrical box and used to brace the shroud. It's exactly the same as the one in the "C" kit. Here's where it gets interesting. One would think that the 'hat' is designed to keep the shroud from bending down and hitting the fan or, if you think like a Crow, it could be to hold the electric box down!
On mine, it is ever so clear that it does nothing AT ALL except take up space. It is too short to be effective.
The foam pad on the top of the hat is pristine.... IT HAS NEVER BEEN IN CONTACT WITH THE SHROUD!!! in the five months it's been in place!
BUT!!! No worries Mr. Coleman!!!
Rest easy in the knowledge that the main refrigerant pipe coming off the compressor is doing yeoman's work keeping your shroud from distorting down into the fan.
The foam cushion I applied to the refrigerant pipe five months ago is flattened and there are wear facets on it and the underside of the bonnet.
I took time to look at the motor mount on the circulation fan. The motor is held in place at each end by a 'C' clamp type mount with rubber inserts for cushioning and vibration control. The squirrel cage is on a stick extending into the air handler. Looks acceptable and satisfactory .....
The clamps on either end of the motor are screwed down tight. There is no space between the clamp 'ears' for any more tightening. Probably made that way for easy assembly.... put motor here.... tighten the screw till the ears touch.
Near certain there is little that can be done to stop any kind of rumble in the circulation fan.
I'll extend a flap of the Crow's wing to PPL RV Parts in Houston for helping get me a "D" fan kit.
I explained that five months ago I ordered a kit and was sent a "C" despite Coleman having "D"s in the logistics trains. So... it took a few weeks but I received a replacement for the "C" .... no charge! Thanks guys!