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Found a good blower motor substitute by harvesting the blower motor from a 1995 Volvo 850. P/N 6820812. This blower motor is available on the Jungle Website for 36$ free shipping. The whole process took me about 3 hours with interruptions. 2 modification are necessary when using this Volvo blower in an a 928. Despite the low price, I don't foresee a false economy becasue the Volvo blower motor seems high quality, appears identical and works as intended. Also, a few hard to find small parts from the Volvo blower car be repurposed, these offer some value for balancing. I had magic blower motor syndrome and no amount of tweaking of the resistor pack helped. When my original blower motor was inspected there was drag on the blower shaft and the commutator was badly scored.
Two mods are needed to use the Volvo blower motor.
1. Shortening of the shaft to 24mm
2. Replacing the male spade connector with a female
Here are some Picts. This project is for an experienced 928 DIY'er and requires a few hours of effort but the results are good and the satisfaction level was high. The better balance of the new fan assembly reduced the slight grumble I had when the fan was on high to nothing. With the old blower motor I'd get magic blower after about 10 min of run time on low, That seems to be resolved, now the volume of air being moved is greatly increased.
If someone sends me a blower and a Volvo replacement I'll make a YT video on how it's done,
First thing to do is harvest Blower motor from the new Volvo Unit.
New motor shaft has to be shortened from 36mm to 24mm using a cut off wheel
Volvo blower motor appears identical, dimensions, weight winding size, and magnet size and over all general design appears the same.
928 blower fan wheel fit on Volvo fan motor with a few gentile taps. The lack of splines doesn't seem to matter.
Tiny weights from the Volvo fan were re-purposed to more finely balance the 928 fan. Porsche techs got the location of the weight right but a bit more was needed to eliminate all the grumble. You can see an intermingling of old and new weights.
Female spade connector needs to be added the brown wire.
Final Assembly
Testing and balance check. Verify polarity of wiring is correct before re-installing the blower assembly back in the 928
Harvest source
Old blower motor and new Blower motor with shortened shaft. Shaft was shortened using a cut of wheel and finished out by running the motor against a flap disk.
Last edited by icsamerica; 02-22-2023 at 10:28 PM.
I've run the blower for some time and all seems OK but the aforementioned current draw situation was a concern. I order an Ammeter to quantify the results and to put some numbers to it and to do some testing. The results were surprising to me. I thought the Volvo motor would draw more based on the amount of air being moved.
Pict 1. Ammeter with no load, shows B+ at 12.2 Volts.
Pict 2. Old blower motor, Shows current draw at 22 Amps, seems high and that high draw may explain why I had magic blower syndrome
Pict 3. Volvo blower motor and 928 blower assembly, shows almost 14 Amps, that seems about right to me based on the wire size going to the blower.
Does anyone know for sure the current draw on an OE blower motor?
All tests were done with the same fresh battery and the Voltage displayed in the 1st pict was at the end of the 2 tests.
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Last edited by icsamerica; 02-23-2023 at 08:20 PM.
The current is limited by the motor acting like a generator and making a reverse voltage (back EMF, it is called) that depends on how fast the motor spins. So if the bearings are going and the motor cannot spin as fast it will draw more current.
I did some digging and found the Volvo 850 Uses a Bosch 0 130 111 134 motor. It still can be found on-line from 52 to 85$. If I ever had to do this again for myself I'd certainly choose the made in Germany Bosch part for the extra 20$. Perhaps I'll order a spare to have on the shelf.
I also found the Chinese knock 'offs for as low as 24$ on eBay that look exactly like what I used.
Last edited by icsamerica; 02-24-2023 at 06:46 PM.
Would this work in a RHD or would connectors require reversing?
Looks promising as it doesn’t have the larger brushes which other alternative motors have, which do not fit housing in my MY91.
I've never actually seen a RHD 928 but I presume the blower is on the other side becasue of the wiper linkage. I also presume only the blower is different in some way, since it has to blow out on the opposite side. More than likely the motor turns the same way but the output is on the opposite side of the housing. I can't foresee anything insurmountable in using the Volvo fan motor on the RHD 928. The difference most likely lies in the housing orientation or the blower wheel's fin orientation in concert with where the air exits so.... game on, give it a go, you're risk in this case is what ever a fan Volvo fan motor costs in UK. If for some reason you had to use reverse polarity I don't think these type of DC motors care.
Last edited by icsamerica; 02-24-2023 at 06:47 PM.
Which Roger motor? My understanding is there were 2 versions sold over the years. Thanks for posting this. At 13.4 amps you're getting almost the same draw I got at 13.75. I presume from the video your engine was running so your voltage was higher so less amps should be required to do the same amount of work than when I did my test at 12.25 Volts with the engine not running. Whatever motor you have I presume it's a similar armature and brush design becasue it has nearly the same draw.
Last edited by icsamerica; 02-24-2023 at 08:06 PM.
02-22-2023, 02:41 PM
36$ Blower motor replacement
