Taipo

I actually meant that the rotor seems to have been turning on the shaft not moving closer and further from the commutator.
If the rotor turns (forward and reverse) on the shaft the relationship between the rotor and commutator will change and this will change the current consumption and power delivered by the motor.
I think it would also make a noise as the rotor turns forward and reverse.

Keith
90 S4
NZ

jon928se

I think Keith may be on the right track here.

I replaced the bearings in one stock Fan motor and somehow during removal of the fan blade from the motor managed to unstick the commutator ring and winding yoke from the shaft. - Some trial and error got it pressed back into the correct place on the shaft and it seemed to work for a while then failed similarly to the Pics above. A small relative back and forwards rotation of the commutator and the winding yoke would quickly cause fatigue of the winding wires where they connecto the commutator segments. .

FredR

Phil,

What we have uncovered to date makes me tempted to take a look although it flies in the face of my policy to leave well alone. It would be interesting if you can post pics showing the differences in the two fan motors fitted on your set if it is not too mcuh trouble. Perhaps DR can then advise if he has seen this on other sets but I doubt he would have removed the fans from the motors if the differences are only visible behind the fan hub.

I presume the fan is retained by a small central nut like the OEM unit?

Regards

Fred

PHIL928

Fred,

I believe that all these fans were the same from date of the first production. I think I just got a bit unlucky...
I'll install the new motor as soon as I get it (1 or 2 weeks) and I'll keep you guys updated.

I investigated whether or not the rotor was able to turn on the shaft and it seems pretty snug. Here's a video:
It looks like the shaft is turning but it's not, it's really tight in the vice. There is a bit of play on the rotor, is that enough to cause this?

It's quite easy to remove the blades from the motors, they are held on with a couple of circlips. Just be carefull they tend to break easily if removed without the use of circlip pliers (like I did haha)
Here's a picture:

FredR

Phil,

Nice pic of your tootsies!

As per my earlier comment I am utterly gobsmacked! Why oh why would anyone fit two diferent concepts like this in one piece of kit? Hopefully Dave might be able to comment whether he has seen this combo previously. Seems to me what I saw on that data sheet is correct. Makes me wonder if I have a smoking gun lurking in there.

On the other hand, the fan module well covers this so I suppose it could be argued that dust and water would have a hard time getting in there but it means squat relative to the two motors being different.

The video clip suggests to me the interference fit has gone and it is only the remnants of the windings that are holding it from rotating altogether- did I read the video correctly?

Regards

Fred

FredR

Phil,

correction on my last sentence - what I was trying to say was "it looks like the rotor is moving relative to what must be a mounting sleeve that sits on the main shaft".

Fred

jon928se

That's enough movement to fatigue the wires connecting the commutator segments to the windings which would lead to uneven running as soon as the first one broke, exacerbating the movement as the rotor tries to accelerate then coast against the constant smooth mechanical resistance provided by the fan balades.

If I remember enough electric motor theory, when the angle between a commutator segment and respective rotor winding changes, you either get less rpm and more torque or more rpm and less torque. One of those (I forget which) would cause the motor to then slow down and try to pull more current than designed whcih would overheat the windings.

Taipo

I also think that is enough play to fatigue the connections, there seems to be ten pole pairs on that motor so that movement could occur up to ten times per revolution (while all the connections are intact).

Keith
90 S4
NZ

FredR

Mark,

The kind of money you indicate being asked ought to be the going rate for a 928 in reasonably nice condition and full working order. What you have in front of you at the moment is worth little given the superficial evidence. If the car has been looked after in the way I rather fear it has then you can probably expect the following hit list:

1. Timing belt/idler wheels/ water pump [$2500 for Porsche main dealer supply and fit recently quoted Oman]
2. Ignition leads [$500]
3. Tires [$1500]
4. Brake discs all round plus pads- [$1500]
5. Engine gearbox mounts [$500]
6. Torque converter bearings [$800]
7. Half shaft boots [$500]
8. Steering rack seals/gaiters [$500]
9. In tank fuel pump [$300]
10. External fuel pump [$300]
11. Rebuilt MAF [$500]
12. Distributor covers/rotors [$200]
13. Auto box filter/ATF channgeout [$200]
14. PSD system flush/refill [$100]
15. Brake fluid change [$100]
16. Air filter [$80]
17. Cooling system flush/recharge [$100]
18. a/c system- compressor strip, clean, new seals, drier unit, new hoses, re-gas [$500]
19. Rear hatch plastic insert [$80]
20. Cooling system hoses [$200]
21. Brake hoses [$200]
22. Fuel hoses [$200]
23. Fuel pressure regulator/two dampers [$300]
24. Fuel injector overhaul [$200]
25. LH computer overhaul JDS Porsche [$500 plus delivery]
26. Torque tube bearings - Black Sea R&D [$500?] can be fitted same time as torque converter bearings
27. Rear wheel bearings [$500]
28. Wiper blades all round [$100]
29. Knock sensors/Hall trigger/ Crank position sensor [$500]
30. Radiator [end tanks vulnerable] [$1000]
31. Replacement for missing fan shroud/fans - 928 Specialists [$500]
32 Oil filter/oil charge [ $100]
33. Black Sea super clamp [$500] or PKlamp [$100]
34. Track rod ends [$200]
35.Ignition switch [$100]
36. Tired suspension units/springs [$1000]
37. Engine/gearbox under tray probably missing [$500]

I can guarantee that if the above have not been changed out they will invariably need to be changed out immediately or in the very near future. If the PO can demonstrate these things in recent service history all well and good but looking at the fan bodge I would say the chances of this are el zippo- this chap probably did the common 928 trick of "doing nothing until the car will not go any more" hence why like this.

My arithmetic tells me that this little lot [probably not totally exhaustive] adds up to about $18k or BD7k. When looked at from this perspective how much is the lump currently in front of you really worth?

The water pump/timing belt item is based on the Porsche main dealer doing this- unless I did it myself I would not trust anyone else and they will most likely only fit parts they supply. direct from Porsche Middle East. Folks like Roger at 928srus will supply you good aftermarket parts for this for around $500 or so if you can fit them.

Also, if needed- a half decent second hand engine delivered will likely cost $12k+ and that only if you can trust the source. My experience in this part of the world is that early GTS engines do not survive- mostly destroyed by TBF.

Complete respray will cost upwards of BD1000, door/sunroof seals- $500, interior reupholstry in leather BD600 upwards depending on quality. depending how far/need to go.

Not wishing to put you off but this realistically is the price of 928 ownership. With nearly 13 years experience backing me up overhere I know what I am talking about. I loved the car from the day I first saw it in 1978 and still get a kick driving it. It is not a cheap hobby but you can minimise costs with prudence.

Finally, another word of caution- I have seen too many 928's seriously damaged in the heads/external top of cylinder chimney due to corrosion brought about by not changing the coolant and/or sat stagnant for too long. These engines do not like stagnation. Just about anyone on this list will tell that the best running/least troublesome examples are the ones that are regularly used.

Trust the above helpful/indicative.

Regards

Fred R

PHIL928

^ hmm wrong thread haha :P

FredR

Ops- posted in wrong thread!

My LH is fried!

PHIL928

Hey Guys,
I fitted the replacement motor and i'm back to being able to drive the car
Today after a 15 minute drive, I got back home, popped the hood to inspect the fans and the new motor's wires were really hot. Too hot to touch pretty much, but nothing was melted. I suspect that the problem that caused the first one to pack up is still there.
The other original motor's wires were hot, but not as hot as the new motor.

Any idea for the cause of this or is it expected?

Thanks!

FredR

Phil,

I presume you are back to two SPAL motors. No idea how your kit was connected up but the Porsche wiring is much thicker than the SPAL wiring tails which means the current will heat the cable up more than stock. Whether this transates to anything noticeable no idea- pity I did not see your post earlier when I was out playing this afternoon- I would have checked mine not thatit means an awful lot.

I take it the fan is able to spin freely [nothing binding]. Presumably you checked the replacement motor rating to ensure it has the same power delivery. I take it there is no way that you could be leaking current to earth in the vicinity of tthe motor?

Nothing else fathoms at the moment.

Fred