Chalkboss

87 S4. Had the dash out before, seemed like the blower was struggling, just not vigorous. But always worked. I have replaced the fan resistor pack recently. After that the blower sometimes does not work in any speed, or any setting. Just dead. Not a fuse issue. Do I need to look at blower (not electrically inclined), or just pull console again and check connections? If I need to test blower can you tell me how?

Thanks.

Schocki

No need to pull the dash again! Check the power supply at the motor directly with a multimeter. Especially at level 4 the fan needs to run.
AFAIK the new resistor packs sold by Porsche are not a direct plug and play. They are for the later models. The plug at the pack needs to be rewired (easy). I have to dig in our German forum but I helped a lady with this not too long ago. After installation only level 1 and 4 worked initially.
If the fan wasn't working that great before, do yourself a favor and order a new motor from Roger. They are original Bosch and a direct drop in. It makes all the difference!
Let me know what you find.

Chalkboss

Thanks Schocki,

It is working intermittently, but now only works at the highest setting (all slider positions inc. defrost). I tested at motor and have no power at lower settings. So either I have a bum connection in between or a bad HVAC unit? It's not been entirely reliable for a few years. Sometimes I push the AC and get nothing. Then it starts working. I'm not interested in doing the relay swap into it and would rather just get a refurbed one if it is the unit.

GregBBRD

You have 2 separate issues, which can drive you nuts when attempting to isolate, if you are not familiar with what failures occur.
Your resistor pack is the cause of the problem with only having 1 speed. If you look at the internal contact at the bottom of the pack (overheat prevention pack), you will see that the original pack had these contacts touching. The new pack has the contacts separated. Unless one of the "resistor coils" are broken, it is very likely that simply cleaning the contacts will "rebuild" your original part and it will work for many more years. Alternatively, you can gently "modify" the new pack by bending the adjustment area of the contacts, so they make contact gently.
Your intermittent A/C problem is the relay in the control unit. Although we used to rebuild these units, we currently are not offering this as a service to vehicles not in our shop. However, Loren at Systems Consulting (in California) does a good job of rebuilding these units.

Good luck!

Chalkboss

Thanks Greg, I did buy a new resistor pack about a year ago and I recall having to modify it although I don't remember what I did. I know it's been working fine until the last month. I'll take another look at it. Thanks for the tip for the HVAC rebuilding.

Koenig-Specials 928

I have Greg's first iteration of the more powerful blower and enhanced wiring kit.
Recently if I try to fast cool the car down at the highest speed (4) the entire head unit and blower/ac shuts down after about 5 minutes.
No fuse gets blown and after a while it resets as if nothing happened.

Is this scenario also pointing to my Resister pack?

Is removing this rubber piece and shoving your hands down inside the only way to replace the Resister pack?

The Forgotten On

I pulled this from a thread https://rennlist.com/forums/928-foru...stor-pack.html post #9

Keep in mind this applies to using the later GTS 01 resistor pack being used in an earlier car. Since I don't know which resistor pack you installed I'm going to assume it was the lower cost newer 01 variant.

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

But seeing that you had no issues until last month it could be something else entirely. Still worth checking though as the wires are easy enough to get to.

Chalkboss

Well here's a case of throwing parts at a problem when you don't fully understand the problem (fan runs at high speed only, all settings). I have recently replaced the blower motor. I pulled the resistor pack out which is only a few years old and cleaned/looked at it while I was in there. Not sure what I was looking at so not much help there. I got the 01 GTS version. I did re-pin it and it was working for months without issue.

So I button it up and turned it on, had all speeds working. I thought, cool, it's fixed. Turned it off, came back later and back to only highest speed working. Decided to replace HVAC head unit with a rebuilt one from Roger. Just put that in and no change, still only works on 4 setting. Any help? I'm not very good at electrics but do have a voltmeter but I'm a novice using it.

Thanks

Chalkboss

Any more thoughts? I swapped relays around and no change. Noticed the blower relay was getting warm. I think I'm going to pull the resistor pack again and clean it thoroughly but I don't know what to look for.

The Forgotten On

^^ The fan switch is an entirely separate assembly you can buy from Porsche independent of the main head unit.

IIRC the fan on full blast can route power through the defrost relay instead of the blower relay (relays 4 and 5 respectively).

I would replace both relays with good new 53s just to be safe.

systemsc

Here's a helpful troubleshooting guide;
I. Basic (no tools required)

a. Move temp slider to minimum temperature - with A/C button "on" compressor should come "on".
Servo unit (above the accel pedal) arm should move to the maximum position (water valve closed
with vacuum - water valve is normally open without vacuum resulting in maximum heat).
Notes:
1. high/low pressure switches must function properly - freon O.K.
2. compressor clutch current from climate control unit (CCU) must be less than 3-4 amps
or the CCU will be damaged.

b. Move temp slider to maximum temperature - water valve should open ( no vacuum) and heat
should be developed. Servo unit arm should move to the opposite maximum position of "a".

c. If either test "a" or the test "b" fails, the problem is not the CCU.
Possible causes for failure; power to CCU, bad servo unit, compressor clutch, water valve,
Freon level/switches, wiring, loss of vacuum.

d. Move temp slider to middle setting - servo unit arm should be @ approximate middle of
positions of "a" and "b". Possible causes; open temp sensors (inside/outside), bad servo unit.

Note: The min/max temperature change (no A/C) with the temp slider is a function of the inside
and outside temperatures; i.e. At very cold ambient temps, the min to max temp change may
be 40 - 50 deg. F. At very hot ambient temps, the min to max temp change may only be
15 - 20 deg. F. Also, an "open" outside temp sensor will cause full heat (no vacuum on water valve).

e. With the blower on max., move the diverter lever (lower) to various positions
and the air should be diverted accordingly. Possible causes for failure; bad servo,
no vacuum, vacuum solenoids bad, and/or vacuum actuators bad.

II. Technical (test light and/or voltmeter)

Measure the various CCU pins and check for proper voltages with the CCU connected.
Pin numbers are only applicable to late 928 CCUs (07/09/11 types). Pin numbers on early
CCUs are different as is the wiring. The CCU pins are numbered from left to right as viewed
from the CCU's side with the CCU upright and horizontal (as mounted in the vehicle) with
the front to your right.

Pin Number Measured Value (volts) (Note: Notch between pins 3 & 4)

3 interior lights "on" power ( 12 )
4 ground ( 0 )
5 compressor clutch power "in" (A/C "on") ( 12 )
6 compressor clutch power "out" ( 12 ), to freon switches then to clutch
7 A/C switch power "in" (A/C "on") ( 12 )
10 CCU power "in", ( 12 ), ignition key "on"
11 power "out", ( 12 ), lower slider @ defrost mode
12 power "out", ( 12 ), lower slider @ "OFF", vacuum to water valve from solenoid (12)
13 power "out", ( 12 ), lower slider @ max heat
14 temp sensors input, must indicate a resistance to ground, not an "open"
15 power "out", ( 12 ), lower slider off of "0"

Chalkboss

Thanks for the above but ac works fine. I have replaced fan blower relays (inc. defrost) and pulled the resistor pack and cleaned it. It's only a few years old. The part no. is 928.616.101.00.

I still get only high speed on the fan. Can someone tell me how to test this? Resistor pack looks fine, no broken wires.

systemsc

You need to use a test light (TL) to check the 5 round pins (left side of CCU) that control the blower fan speed as the **** is turned.

0 position - no pins connected - pin 5, TL on with key on
1 position - pins 1/5 connected & TL on
2 position - pins 1/2/5 connected & TL on
3 position - pins 1/2/3/5 connected & TL on
4 position - all pins connected & TL on

Then use the TL to check for 12V on the resistors as the **** is turned;

Chalkboss

Wrapping this up- after all the headache I swapped in a blower resistor pack and it works now. The one I bought around four years ago failed. Some small, metal tab on the thermal switch just fell off. Strange. Well at least I don't need to worry about the head unit or blower going out. They were getting long in the tooth.