Blower Fan Motor Replacement
03-06-2012, 04:25 PM
#32
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The shaft of the motor is a little longer, the fan needs to be pushed a little further an the shaft for clearance purposes.
Connect the motor before mounting it and check that it runs correctly. I had to reverse the polarity on mine.
You're done!
Connect the motor before mounting it and check that it runs correctly. I had to reverse the polarity on mine.
You're done!
05-18-2012, 01:29 AM
#33
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It seems that every DIY that Schocki posts takes 15 minutes... 
Including this blower motor R&R- if one were in a hurry and didn't clean anything this is literally a 10 minute job. I did this tonight using Roger's replacement motor.
Coupla notes and a coupla pics:
Starting point: Old blower motor shaft is ~2mm below the surface of the fan:
6 clips undone with a small flatblade screwdriver (arrow points to clip for electrical spade connections, also needs to come off). These clips really like to fly, watch your aim.....:
Electrical connections:
Pull the two spade connectors off the motor:
Separate the blower case halves by hand, and undo the 7mm screw holding the motor to the upper half - you'll note the slots in the case that allow the brush housings to fit in the case.
To remove the blower cage from the old motor, I suspended the blower vanes on 2 pieces of wood and hammered the shaft downward with a 1/4" punch.
Trivia: only the Germans would mold compass headings into the fan, and have provisions for adding metal balance pieces to the blades:
A look at the 21 year old motor reveals that about half of the brushes are gone (note the position of the braided lead) and the commutator is quite worn:
The old motor shaft is 137 mm overall, while the new motor shaft is 140mm. So as Schocki points out, the fan needs to slip 3 mm further down the shaft to fit in the housing.
Support the motor on two blocks of wood and press the fan back on the shaft, then one can tap into place with a deep 3/8"-ish socket.
New shaft in the proper position (no rubbing when test-fitted).
I should add that I bench tested the old fan before disassembly- it consumed 16 amps at 12V. The new fan motor pulls 24 amps at 12V, with a noticeably stronger output. So for all the (valid) discussions about cleaning your evaporator, I'd bet that some of the low airflow that people complain about is old tired blower motors.
Including this blower motor R&R- if one were in a hurry and didn't clean anything this is literally a 10 minute job. I did this tonight using Roger's replacement motor. Coupla notes and a coupla pics:
Starting point: Old blower motor shaft is ~2mm below the surface of the fan:
6 clips undone with a small flatblade screwdriver (arrow points to clip for electrical spade connections, also needs to come off). These clips really like to fly, watch your aim.....:
Electrical connections:
Pull the two spade connectors off the motor:
Separate the blower case halves by hand, and undo the 7mm screw holding the motor to the upper half - you'll note the slots in the case that allow the brush housings to fit in the case.
To remove the blower cage from the old motor, I suspended the blower vanes on 2 pieces of wood and hammered the shaft downward with a 1/4" punch.
Trivia: only the Germans would mold compass headings into the fan, and have provisions for adding metal balance pieces to the blades:
A look at the 21 year old motor reveals that about half of the brushes are gone (note the position of the braided lead) and the commutator is quite worn:
The old motor shaft is 137 mm overall, while the new motor shaft is 140mm. So as Schocki points out, the fan needs to slip 3 mm further down the shaft to fit in the housing.
Support the motor on two blocks of wood and press the fan back on the shaft, then one can tap into place with a deep 3/8"-ish socket.
New shaft in the proper position (no rubbing when test-fitted).
I should add that I bench tested the old fan before disassembly- it consumed 16 amps at 12V. The new fan motor pulls 24 amps at 12V, with a noticeably stronger output. So for all the (valid) discussions about cleaning your evaporator, I'd bet that some of the low airflow that people complain about is old tired blower motors.
07-01-2012, 06:52 PM
#35
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Just did this upgrade today - thanks Roger and Schocki for the write ups/photos.
Oh, turns out I had the old style blower housing. I just modified the housing - cut some slots flipped the pieces and plastic welded back together. Looks a little gnarly, but it seals and the motor really puts out some air.
Oh, turns out I had the old style blower housing. I just modified the housing - cut some slots flipped the pieces and plastic welded back together. Looks a little gnarly, but it seals and the motor really puts out some air.
07-09-2012, 05:27 AM
#36
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Just to report another successful installation of Roger's replacement blower motor on a 94 GTS.
BTW, does your HVAC system connects the AC when putting the slider on recirculation mode?
BR
Antonio
BTW, does your HVAC system connects the AC when putting the slider on recirculation mode?
BR
Antonio
07-09-2012, 08:09 AM
#37
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We love you too Roger
There are lots of issues with the HVAC Blower Motor. Most are over 20 years old and they can become noisy or stop working all together. Up until now the only solution was to buy new at circa $600 or buy a used unit with possibly the same issues. Another alternative offered was to modify the body of the blower to accommodate a new motor.
928sRus and friends have developed a “plug and play” solution using a new Bosch blower motor that requires no modification.
Remove the six clips (flat bladed screwdriver) holding the two halves of the body together. Remove the clip holding the electrical box cover in place. Disconnect the two contacts from the motor. Remove the bolt holding the motor into the blower body. Remove the squirrel cage from the splines on the old motor. Replace on the new motor and ensure the shaft is protruding slightly from the bush. Place the motor and cage assembly into the blower body and check that the cage runs smoothly and there is clearance. Assembly is the reverse and you are in business.
Higher speeds and increased flow over the old worn out motor are the benefits.
Price for the new motor is $169.95 plus shipping.
Pictures to be posted later – camera software not compatible with Windows 7.
Some cars 77 to 81 came with an earlier style blower which may or may not accept the new motor. We will try one this week to see if it works. The newer blower is backward compatible with the earlier style.
There are lots of issues with the HVAC Blower Motor. Most are over 20 years old and they can become noisy or stop working all together. Up until now the only solution was to buy new at circa $600 or buy a used unit with possibly the same issues. Another alternative offered was to modify the body of the blower to accommodate a new motor.928sRus and friends have developed a “plug and play” solution using a new Bosch blower motor that requires no modification.
Remove the six clips (flat bladed screwdriver) holding the two halves of the body together. Remove the clip holding the electrical box cover in place. Disconnect the two contacts from the motor. Remove the bolt holding the motor into the blower body. Remove the squirrel cage from the splines on the old motor. Replace on the new motor and ensure the shaft is protruding slightly from the bush. Place the motor and cage assembly into the blower body and check that the cage runs smoothly and there is clearance. Assembly is the reverse and you are in business.
Higher speeds and increased flow over the old worn out motor are the benefits.
Price for the new motor is $169.95 plus shipping.
Pictures to be posted later – camera software not compatible with Windows 7.
Some cars 77 to 81 came with an earlier style blower which may or may not accept the new motor. We will try one this week to see if it works. The newer blower is backward compatible with the earlier style.
09-11-2014, 09:27 AM
#40
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It removes the moisture from the air. Same with defrost. A/C dries the air blown on the windshield to faster remove the moisture that is there.
09-11-2014, 12:52 PM
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I put in one of Roger's kits. Had the old style housing, so I picked up a new style blower cheap off FleaBay when the opportunity came up.. Great upgrade,, much better air movement and A/C effectiveness... with a black on black car, all the better....
09-11-2014, 02:06 PM
#42
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The dedicated defogger will remove interior windshield misting (caused by humid air and a cold windshield) very quickly - but it always works more effectively with the console & door vents closed.
If the rear screen or windows are misting up repeatedly (even with rear defogger on) turn on the AC - AND increase the cabin temperature a little.
Alan
09-11-2014, 02:44 PM
#43
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I think worth mentioning is that the replacement fan motor draws more current than the old fan motor.....and the size of the wire that feeds the motor is inadequate for the amount of current passing through it.
The factory used 2.5mm wire to run from the connector to the fan motor and this is adequate. Unfortunately, they used 2.0mm wire to provide power to this connection and this is, apparently, just a little bit too small to carry the current for the upgraded fan motor......as it gets very, very hot.
For all of you grabbing the factory wiring diagram to confirm this...there's also an error in all of those diagrams. The diagrams show a 2.5mm wire coming from the blower switch to the resistance group connector (terminal 2 on the blower switch to terminal 8 on the resistance group). While this is true for early vehicles, I've yet to find a 1987 and later vehicle with this larger wire. Both black wires are 2.0mm on every "late" vehicle I've looked at (and I've looked at many, to verify this discrepancy.)
I installed several of these fan motors, before I discovered this problem. I found that the white plastic connector and the wires from the chassis to that connect to this connector got so hot that the connector would get so hot you couldn't touch it....and would discolor in a matter of days. The vehicle that I "found" the initial problem on actually had smoke coming off that connector when the fan had been on high speed for 15 minutes or so.
Initially, I thought that the connectors we just old and were not making good enough contact, so I replaced the terminals with fresh ones and re-tested. The heat problem was not cured. I then traced the ground connection for this motor and decided that it was too far away and too small, so I made a connection closer to the source and with larger wire. Still had a connector too hot to touch.
I eventually decided (I'm a far, far cry from an "electron wrangler"....most days, I'm happy if I can get the battery looms hooked up to the proper post!) that the power wire to the actual fan was inadequate for the current draw....through both the defroster and the HVAC side of the circuit. The result was a supplementary wiring loom with a relay, which solved the overheating connector problem.
I "recalled" every vehicle that I'd already installed a new fan motor in. Every single vehicle had "discolored" connectors where the fan motor loom plugs into the main harness and required the upgraded loom with relay.
Roger sells the loom upgrade, also.
The factory used 2.5mm wire to run from the connector to the fan motor and this is adequate. Unfortunately, they used 2.0mm wire to provide power to this connection and this is, apparently, just a little bit too small to carry the current for the upgraded fan motor......as it gets very, very hot.
For all of you grabbing the factory wiring diagram to confirm this...there's also an error in all of those diagrams. The diagrams show a 2.5mm wire coming from the blower switch to the resistance group connector (terminal 2 on the blower switch to terminal 8 on the resistance group). While this is true for early vehicles, I've yet to find a 1987 and later vehicle with this larger wire. Both black wires are 2.0mm on every "late" vehicle I've looked at (and I've looked at many, to verify this discrepancy.)
I installed several of these fan motors, before I discovered this problem. I found that the white plastic connector and the wires from the chassis to that connect to this connector got so hot that the connector would get so hot you couldn't touch it....and would discolor in a matter of days. The vehicle that I "found" the initial problem on actually had smoke coming off that connector when the fan had been on high speed for 15 minutes or so.
Initially, I thought that the connectors we just old and were not making good enough contact, so I replaced the terminals with fresh ones and re-tested. The heat problem was not cured. I then traced the ground connection for this motor and decided that it was too far away and too small, so I made a connection closer to the source and with larger wire. Still had a connector too hot to touch.
I eventually decided (I'm a far, far cry from an "electron wrangler"....most days, I'm happy if I can get the battery looms hooked up to the proper post!) that the power wire to the actual fan was inadequate for the current draw....through both the defroster and the HVAC side of the circuit. The result was a supplementary wiring loom with a relay, which solved the overheating connector problem.
I "recalled" every vehicle that I'd already installed a new fan motor in. Every single vehicle had "discolored" connectors where the fan motor loom plugs into the main harness and required the upgraded loom with relay.
Roger sells the loom upgrade, also.
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greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
Last edited by GregBBRD; 09-11-2014 at 04:02 PM.
09-11-2014, 03:40 PM
#45
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We only sell the blower motor with Greg's new harness.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
