There's three types of resister packs for the 928 S/S4/GT and one for the late GTS models.
928 618 101 01 is the resistor pack for
pre-1989 cars
928 616 101 00 is for the 1989-1993 cars
928 616 101 01 is for the 1994-1995 cars
On top of that there was a change in the wiring of the resistor packs. A pre 1989 version and the one starting 1989.
The pre-1989 has a thermo switch that switches full power to the fan for cooling down the overheated resistor pack. The "magic blower syndrome"
The starting 1989 version is similar, but has a thermo switch that now interrupts the power to the fan to let the resistor pack cool down. It shuts down the fan.
The thermo switch itself is different as it opens when hot instead of closes when hot.
The '94/'95 resistor pack is quite different to the earlier ones - it
doesn't even mount in the plenum (due to pollen filter) - only has 4 pins used
and 3 resistor elements. Speed 0 for these cars is really off (no blower) for
all other models Speed 0 is just a very low speed mode (though some still allow
an off mode via the blower relay controlled by the head unit off mode).
The '89-'93 model that Dan has as a replacement(?) is incompatible with the
earlier model only due to its pinout - it actually has the same features and
mounts in the same manner. It does not have a bimetalic strip to bypass the
resistance group* - instead it has a series thermal switch - if it gets too hot
it just turns off (full speed mode still works via the switch & DEF).
Older versions switch to full speed via the bypass when they overheat (aka
"magic blower syndrome").
Since the early version is NLA - the available '89-'93 version can be
substituted with some pin swaps in the blower socket - this is what Don has done
- but he seems to be having some issues with this.
I believe the '94/'95 version could also be used in earlier cars - however I've
never really written about this - The pinout of this model is MORE different
than the others.
Alan
============
This is for a up to 1984 model:
==========
There is is a bi-metal switch protection circuit in the resistor pack to keep
it from overheating should the air flow be restricted. The bi-metal switch can
sometimes fail, but might be repaired without having to buy a new part.
Also, the resistor pack was redesigned but the newer part is not interchangeable
with the old. My 90' S4 had the wrong resistor pack installed when I bought it
which was causing a blow speed problem. 928 616 101 00 is the resistor pack that
Don has in his car
928 616 101 01 is for the 94 to 95 cars.
Why will the 01 not work? Its cheaper than the 00.
------------
The '94/'95 resistor pack is quite different to the earlier ones - it doesn't
even mount in the plenum (due to pollen filter) - only has 4 pins used and 3
resistor elements. Speed 0 for these cars is really off (no blower) for all
other models Speed 0 is just a very low speed mode (though some still allow an
off mode via the blower relay controlled by the head unit off mode).
The '89-'93 model that Dan has as a replacement(?) is incompatible with the
earlier model only due to its pin out - it actually has the same features and
mounts in the same manner. It does not have a bimetallic strip to bypass the
resistance group* - instead it has a series thermal switch - if it gets too hot
it just turns off (full speed mode still works via the switch & DEF).
Older versions switch to full speed via the bypass when they overheat (aka
"magic blower syndrome").
Since the early version is NLA - the available '89-'93 version can be
substituted with some pin swaps in the blower socket - this is what Don has done
- but he seems to be having some issues with this.
I believe the '94/'95 version could also be used - however I've never really
written about this - The pin out of this model is MORE different than the
others.
If Don has the '94/'95 versions - he's using the wrong instructions....
Alan
__________________
1994 928 GTS Black/Black Manual "AZ Desert Gang"
------------
Roger, I thought the pack I got from you was for 89-93 originally. Sounds like
the 94-95 pack is very different. Looking at the wiring diagrams, the 89-93 is
only slightly different and many here have successfully rewired the plug and
used this pack with success on older cars.
Borland says 3 types: 78-88, 89-93 & 94-95
Borland,
__________________
Don Carter
--------
OK Don - if you have the '94/'95 unit and assuming it fits in the plenum in the
same way and has the same pin out designation (check this - I haven't looked)
these are the swaps you need to do.
Note these instructions are only good for mounting a '94/'95 unit in a <'89
vehicle.
White wire stays on Pin1 (no change)
Move White/Green wire from Pin 5 to Pin 3
Move White/Blue wire from Pin 7 to Pin 4
Move the 2 Black wires from Pin 6 to Pin 2
Leave the Red/White & Red wires on pin 8 (they will not connect to anything)
Move the Red/White wire on pin 4 to pin 5, 6 or 7 (it will not connect to
anything)
(its possible the pairing of the wires on pins 4 & 8 will be reversed - doesn't
matter - what I listed is what's in the wiring diagrams - I think in practice
pin 8 has just the Red/White and pin 4 has the Red/White & Red (functionally
this is the same -> its the same red/White wire)
Alan
----------
The pack I have is almost identical to the pack I took out. 7 pins (socket 3 is
empty), socket's numbered the same way and the pack mounts exactly the same way.
The new pack had a cage around the coils, old one didn't, but it could have been
removed in the past.
Alan, are you saying the '94/'95 pack only has 4 pins, or only 4 pins are used?
If it only 4 pins, then I don't have it, I have 7.
__________________
Don Carter
-------
Don - no its likely to look exactly the same but have only pins 1-4 connected to
anything (you can check this with a DMM on ohms mode) if the part number is 928
616 101 01 it is for the '94/'95.
Alan
======== 
OK so if you replaced an '86 resistor pack with an '89-'93 version it will
not work correctly without modification. Since the <'89 version seem to be NLA I
assume this is what happened?
The pin out and function is different. The function can still be compatible with
some slight modifications:
'86 Resistor Pack Configuration (Pin# / Wire Color / Function)
1 WT Blower Switch I-IV (SW1)
2 NA Same as Pin 6 (not used)
4 RE Feed from Blower relay
5 WT/GN Blower Switch II-IV (SW2)
6 BK Blower Motor Switch IV (SW4)
7 WT/BL Blower Switch III-IV (SW3)
8 RE/WT Thermal bypass - linked to Pin 4
'89 Resistor Pack Configuration (Pin# / Wire Color / Function)
1 WT Blower Switch I-IV (SW1)
2 NA Same as Pin 6 (not used)
4 RE Feed from Blower relay
5 WT/GN Blower Switch II-IV (SW2)
6 NA (not used)
7 WT/BL Blower Switch III-IV (SW3)
8 BK Blower Motor Switch IV (SW4)
So bottom line:
On the connector for the resistor pack cut/remove the RE/WT link between pins 4
& 8
Swap the terminal pin connected to the 2 black wires in pin 6 of the connector
over to pin 8 of the connector - leave pin 6 disconnected. The terminal pins can
be moved in the connector without soldering...
Alan
========
resister pack new style
There are 4 resistance coils in the blower resistor, marked 0.25, 0.4, 1, and
2.5 ohms.
Here's a close up picture of the 4 coils and the marked resistances. Regarding
the coils, I'd bet they're nichrome wire, in three different thicknesses and
lengths as follows:
0.25 ohm coil: 0.9 mm wire (19 gauge), 8.25 mm OD coils, 4.5 turns
0.4ohm coil: 0.7mm wire (21 gauge), 7.8 mm OD coils, 4.5 turns
1 ohm coil: 0.7 mm wire: 9 mm OD coils, 11.5 turns
2.5 ohm coil: 0.5 mm wire (24 gauge): 11.2 mm OD coils, 12.5 turns
------
This is the last version 928_616_101_02 which is used in the 1994/1995 model.
====
This conversion document should be quite helpful: Blower-Resistor-Pack-Swap
=====
Its unclear why this switch is damaged like this - it is very well protected
by the cage & surrounding terminals which makes mechanical damage after assembly
quite unlikely. Electrical overstress also seems unlikely to cause this
kind of dislocation. Handling damage during assembly or parts handling, or parts
quality issues seem more likely.
I can say with this specific damage this unit will function ~normally in a '78 -
'89 car - BUT without any kind of thermal protection. It would not work at all
in a '90 - '93 car (just as if no blower resistor was installed).
Conversely this unit with a fully functional NC switch would work properly in a
'90 -'93 (with thermal protection), but it would not work in a '78 -'89 car (the
blower would run on high all the time without wiring changes).
For a fully functional unit the wiring at the blower connector on a '78 - '89
car could be adapted (as previously described) to get a fully functional version
to work properly with thermal protection.
There is evidence of another 928.616.101.00 working on an '86 car reportedly
without wiring changes which would suggest that car's resistor pack was in fact
damaged in this exact same way (so no thermal protection).
Roger also reports many returns of 928.616.101.00 for '78 -' 89 cars which
suggests many are also not damaged in this way. Only testing a volume of new
stock on hand would reveal how common this fault is.
The test here would be to see if Pin 6 & Pin 8 are connected (continuity test),
if yes the thermal switch could be presumed functional, if no the switch is
certainly non-functional.
Some background here:
Resistor Pack Evolution:
========================
1) 1978-1989* 5 blower speeds: 0,1,2,3,4 (4 bypasses Rx pack) Overheat Thermal
bypass to speed 4
2) 1990*-1993 5 blower Speeds: 0,1,2,3,4 (4 bypasses Rx pack) Overheat Thermal
cut-out (for speeds 0-3), changed connections on car side
3) 1994-1995 4 blower speeds (speed 0 is off) 1,2,3,4 (4 bypasses Rx pack) No
thermal device, changed connector on car side
The car side wiring is different between 1), 2) & 3), with even a quite
different connector type on 3)
1) & 2) share the same connector type and the pins can be rearranged to adapt
connections .
The 1994-1995 resistor pack is not in the plenum (plenum redesigned for pollen
filter) it is instead mounted where the intensive washer tank used to be near
the wiper motor
Resistor Packs 3 Basic Types:
****
Part Numbers: (Roger please verify)
===================================
1) 1978 - 1989* Cars - 928.618.101.00 (NLA) (I'm assuming this was the 1st
number) No direct superseding replacement seems available
2) 1990*- 1993 Cars - 928.618.101.01 (NLA) SS -> 928.616.101.00
3) 1994 - 1995 Cars - 928.616.101.01 (NLA) SS -> 928.616.101.02
Porsche Claims 928.616.101.00 also Supersedes for '78-'89 cars however I believe
this not possible with this configuration (works only if the NC thermal switch
is damaged OC & inoperable).
[* Note also the transition year 1) -> 2) is shown for ordering as '88->'89,
however based on the wiring diagrams I believe it is actually '89->'90 (can
anyone confirm this?)]
Porsches Wiring Mistake:
====================
In changing thermal switching from Parallel NO (Bypass) to Series NC (Disable)
Porsche chose to keep the thermal switch in the same place in the module: Pin 6
and Pin 8 as for the previous NO switch
To accommodate this they changed the car side wiring to the blower resistor Vs.
the '78 - '89 cars this was really a poor choice.
Porsche would have done better to place the NC switch between the 0.25W resistor
& Pin 6 in the updated resistor pack and leave the car wiring the same.
See generic example below & keep it simple.
*****
This configuration (with the Prev. NO switch removed) would have been compatible
with the earlier cars thus making "a Disable" functionality available for
retrofit.
Stock mgmt. would have been easier as a single superseded SKU could directly
cover all previous vehicles while providing a solution to Magic Blower Syndrome
on early cars.
At this point though since the installed wiring IS different between '89->'90
this is not an option. A single SKU for both isn't possible now without major
added complexity AND some trade offs, or by removing thermal protection.
The only option to safely use an NC type Blower Pack on a '78 - '89 car is to
find a fully functional resistor pack and rewire the blower connector.
Porsche would clearly like to have a single SKU for this part across all years -
but they simply DON'T have one. I wonder if in testing this empirically for
function on an early car they happened to used a device with this exact failure?
Alan
====
Throughout this thread there is some confusion about the year breakpoint between
the early years resistor pack and the mid-years resistor pack. This is because
in the parts ordering details it is shown as 1988 -> 1989 and in the wiring
diagrams configurations it is shown as 1989 ->1990. Normally the wiring diagrams
are very reliable - at least about major functional changes - and so I placed
more credence in that detail. However in this case it has been shown that the
changeover did occur between 1988 ->1989 so the wiring diagram is just incorrect
for 1989, and the ordering details are correct.
The above threads are now too old for me to now edit & correct . But here is the
corrected summary again:
Updated for correctness
Reiterating what Roger initially posted (which was already correct for the year
transition):
928 618 101 01 was relevant for 78 to 88 and became unavailable for a period of
time and Porsche SS it to 928 616 101 00 (this an incorrect supersession and it
is not functional for these years)
928 616 101 00 was relevant for 89 to 93 cars only originally. (Still is only
applicable to these years - unless the connector is rewired - however many
quality issues seen with current supply valid as of early 2025)
928 616 101 01 was relevant for 94 to 95 but now SS to 928 616 101 02 for 94 to
95.
A further clarification is that for the few '94 GTS cars with M718 option code
the Mid-Years pack applies as these cars were built like the '93 models and sold
as '94 models (wrt VIN)
Alan