Gama

I have become the proud owner of a 89 s4 which has what I believe is a fault with the Radiator fans. They come on as soon as the ignition is turned on and after the car has reached operating temperature and has been switched off they remain on for maybe half an hour (not good for battery). I am used to working on lot simpler cars and have to admit looking under the bonnet of my porsche leaves me feeling rather intimidated. I have yet to aquire a shop manual. Could this be a problem with the Temp Sensor? If so where is it situated?
Any help would be much appreciated.

Ta
Mark

dr bob

Gama--

Welcome to the group and to 928 ownership. IMHO, the 1989 car is perhaps the best of the breed; You have selected well!

On to your question--

There are a few things that can case what you are seeing.

The principal operation of the fans is managing engine coolant temp. The sensor used for the fans is located on the bottom front left (driver's side on US cars) of the radiator, accessible under the AC condenser. Works only with key on. Fans run at any of three speeds depending on coolant temp.

The AC system is monitored for freon pressure, with a transducer mounted on the receiver/drier, right front of car in front of the AC condenser. This is the upper sensor on that plumbing on my car. When AC is on, fans will run at any of three speeds depending on refrigerant temp as determined by its pressure.

There's an intake manifold temp switch mounted in the middle of the top of the intake manifold. It's intended to relieve some hot-soak heat problems after the engine is shut down. Works whether the key is on or off. Fans run at low speed when the switch is closed.

If you have an automatic transmission, there's a temp switch on the trans that helps protect it from overheating. Works with key on or off. Fan runs in low speed when the temp switch is closed.


The sensors connect to a controller module that's located under the cover on the side of the passenger's seat area. Under that cover you'll also find the audio amp. The fan controller is the forwatd module that says Hella on it. Fan speed signals from that module are sent to an amplifier/wsitching module located on the right front (pass side on US cars) apron at the front of the engine bay under the hood. Look next to the hood latch, at that black finned unit with the round plug on top. A screw and little finger bracket retain the connector plug.

Primary power wiring comes directly from the battery (in the rear of the car under the spare tire area under the luggage area) through dedicated feeds to the central electrics panel on the passenger side floor area, through fuses 28 and 29, to that amplifier module.


The workshop manuals have a diagnostic process. You can get a CD set of them from Jim Morehouse here on the list, along with the tech pubs and service bulletins, and a lot of other very useful info needed to keep the car alive and happy. Search for Jim in the user's list and PM him for info.

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Rennlist membership will be a key to your longer-term enjoyment of the car. It's really cheap, and adds some features like the search functions that let you find and read posts and solutions from others who have passed this way before you. Invest now for your future enjoyment!

Gama

Dr Bob

thanks for your detailed reply. The fans do switch to a lower speed when the ignition is switch off. Would this observation help me narrow down the culprit? I will get hold of jim too.

Hilton

Hi Mark welcome to 928 ownership.

You might want to go look at this site in the UK. It should help demistify things

dr bob

The first thing to try would be disconnecting the wires on the temp switch at the top of the intake manifold. This should eliminate the fans running after the ignition is off. The failure mode for that switch is closed it seems, causing what you are seeing. That's often the result of washing the engine or otherwise getting water on the switch. Swiath is easy to replace-- just unscrew the old one and screw the new one into the same place. No coolant under the switch so everything stays dry.

Where are you located?

Gama

Im a Kiwi boy living Just north of Auckland, New Zealand.

I didnt quite appreciate how understated these cars are in NZ. Since ive Aquired this beast, everybody is shocked to learn its V8 powered, with a frightening top speed. Certainly placed a few smiles (and a few white knuckles) on a few of the lads faces after a quick Fang.

Thanks for the link Xlot. Dr Bob, I have given the engine an initial hose down prior to giving it a good clean (although the previous owner serviced the car regularly, he was not hot in the cleaning department) seems I may have disturbed the setup by doing this. More Questions if I may.

1) Are 928's sensitive to engine cleaning?(High pressure water gun at a safe distance?)

2) The Sensor you are refering to is the one on top towards the back of the manifold?(just to make doubly sure im reaching for the right one)

3) Two Sensors in front of the intake, connected to cooling system plumbing. What's the purpose of these two?

4) Is there a way of disabling the Brake Pad service warning (Ive found the work around for Tire pressure warning but cant find the one for the Brakes)

5) The Bonnet Hydrolic arms are stuffed. Does any body know how to fix these?

dr bob

[QUOTE=Gama;4659541]Im a Kiwi boy living Just north of Auckland, New Zealand.

I didnt quite appreciate how understated these cars are in NZ. Since ive Aquired this beast, everybody is shocked to learn its V8 powered, with a frightening top speed. Certainly placed a few smiles (and a few white knuckles) on a few of the lads faces after a quick Fang.

Thanks for the link Xlot. Dr Bob, I have given the engine an initial hose down prior to giving it a good clean (although the previous owner serviced the car regularly, he was not hot in the cleaning department) seems I may have disturbed the setup by doing this. More Questions if I may.

1) Are 928's sensitive to engine cleaning?(High pressure water gun at a safe distance?)
/quote]

They can be especially as they age. The wiring gets dried out, connectors crack, and water has an easier time finding places to sit. I don't hesitate to clean the engine, just go gentlly with the water spray.


That's the one. Brown wire and a brown/green wire if I remember correctly.


One is feeding temp signals to the ignition brain (EZK) and the fuel management brain (LHA). IIRC, that's the one on the left as you look at the front of the motor. Dual-element thermistor-type sensor. The other one feeds the gauge and the temp light.

Easiest way is to install pads that have some thickness to them, and at the same time replace the wear sensors that are clipped into notches in the pad backing plate. The senors are simple wire loops embedded in plastic shells. The wire loop wers therough from rubbing on the rotor. The open loop then causes the warning lamp to illuminate. You can cut the wires going to the sensors and close the loops, but then you have no protection. The sensors will wear through before pad depth is less than about 5mm. That looks like a lot of pad left but doesn't quite keep up with a few high-speed braking sequences without fade.

There are replacements available from third-party parts suppliers. Right now the US dollar is weak so it's a great time to order your parts from the US. I suggest that you drive the car a bit and make a list of parts you'll need, then order from one of our begger suppliers. My favorite is 928 International, online at www.928intl.com They do a lot of international orders to your neighborhood. Last time I looked the hood struts were less than US$20 each. Look at the struts on the rear hatch also-- they are typically the same age. Installation is minutes, slide back the little metal retainer clip around each ball coupler, and the old strut pops off. New one pops right on to replace. So you'll need four struts, pads for 4 wheels, possibly rotors, need the pad sensors and the sticky retainers for the pads. Plus all the other things you discover in the next week or two.


There's an active 928 owners' group in neighboring Australia, and some other cars have made it to NZ besides yours. So you're not alone there. I'm sure some of the other NZ owners will chime in with a welcome.