From: V1UhOh@aol.com
Sent: Friday, June 23, 2000 12:08 AM
To: 928
Subject: [928] Re: 928 is playing games with me
hey steve
There is a resistor pack in the blower tunnel..under the rainshield...
....to cut it short there is a bimetal strip in the resistor pack that when
the tunnel area gets too hot the strips bend and make contact and turn on the
blower to a MAX setting overiding the switch...basically sounds like magic
blower syndrome. I got sick of this gremlin especially in Vegas
ie. on a nice cool day....intense sun on my car....tunnel gets hot...turn
the key and instant hi flow hot air!!
as a last resort Ive had my bi metal contacts "isolated" so they will never
touch. (amounted to putting a piece of tape between the two contacts) Perhaps
a no no...but it works and im insured and the blower genie is not to be seen.
Tony
try My 1987 Porsche 928 S4
under airrecirculation flap
From: Wally Plumley [wplumley@avana.net]
Sent: Friday, July 21, 2000 2:35 PM
To: 928
Subject: [928] Re: A/C System Problems
At 09:36 AM 7/21/00 -0600, Erik Behrendsen wrote:
>On the way out to Wichita I lost the use of the first three speeds of the
>blower fan, (with or without the A/C on.) Then about 2-3 minutes later the
>fourth speed dies and NO A/C . I did a little digging around and found that
>the # 17 fuse (30amp) was blown, so I change that. First three speeds still
>didn't work, but the four one did, at least for about 45 seconds and then it
>blew again. Now, during the time that it was working it sounded like the
>blower fan was having a little trouble but I don't know if that's related to
>the first three speeds not working or not.
You appear to have either a short circuit inside the blower resistor pack
(most likely), a short circuit in the wiring to the blower, or (less
likely) a blower motor that is pulling much too much current.
I would start looking at the resistor pack in the HVAC plenum under the
plastic cover under the hood at the base of the windshield.
If you have problems finding the short circuit, one way of testing is to
take a blown fuse and solder a small 12 vdc light bulb across the tiny tabs
on the face of the fuse (you will probably have to cut away some of the
plastic). When you plug the light into the socket that blows fuses, it will
allow enough current to pass to allow troubleshooting, but not enough to
burn anything up.
Wally Plumley
928 Specialists
From: "Jolanda & Oscar"
Date: Sat, 7 Jul 2001 10:54:08 +0200
Subject: [928OC Public] How to replace the bimetallic switch ?
Hi list !
My problem is a common one: My blower only works on "4".
Thanks to the list, I know what the problem is. Here in Holland this
switch costs about $120 .
I ordered the part (928-616-101-00) and now I have to install it.
In my archives the only instruction on this issue was: "I installed the new
switch and...".
Well...that doesn't do it for me, I'm afraid. Can somebody please instruct
me on how to install this switch.
Oh....I'm not a mechanic, so please don't let me remove the hood ore
something.
Thanks in advance
Oscar
'92 928GTS manual grand prix white
From: Kurt Rottner [kurt.rottner@gmx.net]
Sent: Sunday, July 08, 2001 11:02 AM
To: '928@list.928oc.org'
Subject: [928OC Public] How to replace the bimetallic switch ?
Oscar,
I did this long time ago, so I hope I recall everything:
First: you DON'T need to take off the hood!
Peel off the rubber lip which holds down the black fan cowling and
carefully pull the cowling out to expose the "area of interest".
The resistor block is visible from it's connector-side, sticking out from
an air duct. The problem is that the opening is not large enough to take it
out, though.
Place a shop rag to prevent the bolts from getting lost. Take off the
connector and loosen the bolts ( I think there were two) There is a rubber
sleeve which connects the blower motor to the air duct. Pull this sleeve to
the side, far enough to get the resistor block through. Push a wire through
this opening and hook it to the resistor block to pull it out. The new
block goes in the same way, using a second wire hook to pull the block into
it's place.
The rest should be straight forward.
One word of caution: the anti-iceing capillary of the A/C is pretty close
to the fan resistor block, be sure not to bend or break the capillary when
working on the resistor block.
BTW: Don't throw away your old resistor block. It is normally corrosion of
the bimetallic switch that causes trouble. Cleaning these contacts makes it
ready for a new go once the "new" switch fails ;-)
Hope that helps
Kurt
90 S4 Auto
-----Original Message-----
From: Wally Plumley [mailto:wplumley@bellsouth.net]
Sent: Friday, March 08, 2002 9:56 AM
To: 928
Subject: [928] Re: Need advice on Fan Blower problem
At 02:47 PM 3/7/02, Lee, Howard S wrote:
>I have a blower problem on the climate control system which I would
>appreciate your advice to help fix. It was working fine last week.
>Noticed yesterday that the blower only works when the fan switch is
>at the highest setting, 4. Does not blow at any other setting.
>A/C, Heat, Temp and Vent controls seem to be working normally. Rear
>A/C, blower system seems to be working normally.
>
>Is this problem due to the documented resistor pack issues? I'm not
>sure since the maximum blowing isn't intermittent, and still coming
>on only at setting 4.
Two different resistor pack problems.
The blower motor is powered in two different ways.
The speed knob sends power thru different combinations of wire resistors in
the resistor pack mounted in the blower plenum under the hood. Top speed
bypasses all of the resistors. If the blower does not run on any of the
lower speeds, but will run on 4, the problem is usually a broken resistor
wire or bad connection in the resistor pack.
The blower motor has an independent power source thru the DEFROST setting.
If the blower will not run on any knob speed, including 4, but will run on
DEFROST, the problem is probably either the blower relay or fuse.
The "magic blower syndrome" is different. Inside the resistor pack, there
is a thermal switch that bypasses the resistors, running the blower at full
speed. Apparently, Porsche engineers were concerned about overheating the
resistor pack or the plastic plenum where it is mounted. If the blower is
on a low speed, with low airflow thru the plenum, and perhaps the blower
motor is pulling more than normal amperage due to bad bearings, the
resistor pack can overheat. The thermal switch will close, bypassing the
resistors, and the blower motor will go to full speed. The increased
airflow will cool the resistor pack and the thermal switch, the switch will
open, and the blower will go back to a low speed.
if the thermal switch gets too sensitive, the blower will continually be
switching to high speed and back by itself, thus the "magic blower
syndrome". The cure is to take the resistor pack out and adjust the thermal
switch, or to replace the resistor pack.
Wally Plumley
928 Specialists
www.928gt.com