1987 944S 16V cooling fan wiring - single fan to twinfan

[Evil Dan]

My car is a bit of anoddity that it is an oval dash 1987S with a single cooling fan, the thermo switch in the radiator is 2 wire but it has the twin fan relay in the fuse box.

The engine has been swapped to an S2 but the cooling was left as 2.5 NA with single fan.

I want to upgrade to the turbo / s2 twin fan setup.

Does anyone have any advice on what wiring I will need to alter? Has anyone else had the odd single fan set up on the 1987 S?

The wiring from the temp switch in the rad is only 2 wires, when the fan comes on its high with ignition on or slow with ignition off. I will need to add another wire here for the slow speed, where does this connect into the loom/ harness at the fusebox?

As far as I can see there is only wiring for one fan so unless the factory harness will have been tucked away somewhere I'll need to add a second wire pair to the second fan, where does this connect at the fusebox/ relay side?

Thanks in advance!

[Eskozki]

Sounds like you have similar situation as I have. I have a 86 late model with a 2-wire thermoswitch and I couldn't find the 3rd wire needed for a real late model thermoswitch. I had the electrical drawings somewhere, I'll check where I saved them when I get home. I ended up wiring a switch inside the cabin to trigger the highspeed fan as the thermoswitch only triggered the low speed. Check clarks-garage.com for some trouble shooting.

But I thought that all 944's came with twin fans? Only on the earlier model one fan will only start if the thermoswitch closes and energizes the cooling fan relay. Can you take a pic of your cars fan and thermoswitch?

[944 Ecology]

Cars without AC came with only one radiator fan.

[Evil Dan]

Yes it was UK RHD spec without AC, one cooling fan.

It runs on high speed so I guess with the standard 2.5 it would have been ok for cooling but when they swapped in the 3.0 they should have changed the Rad and fans!

Does anyone have a pin out for the 2 speed fan relay?

Are both fans ran off the same circuit at fast or slow speed or is each fan switched on and off independantly?

I'm tempted to just jump the second fan from the single fan wiring but would prefer to wire it to the intended origin in the harness or fusebox.

[Eskozki]

This is what you need?
http://www.clarks-garage.com/graphics/cooling_fan_late_1.jpg

[walfreyydo]

This page runs you down how the cooling fans work between the different years and models, with AC and without. All late model 944 85.5+ have a dual fan setup according to Clarks
http://www.clarks-garage.com/shop-manual/cool-01.htm

Factory Service manual and electrical diagrams:
http://p914-6info.net/944%20Manuals.html

[walfreyydo]

Originally Posted by 944 Ecology

Cars without AC came with only one radiator fan.

Only true on early model cars according to Clarks - but maybe thats for USA models only?

[walfreyydo]

Originally Posted by Evil Dan

My car is a bit of anoddity that it is an oval dash 1987S with a single cooling fan, the thermo switch in the radiator is 2 wire but it has the twin fan relay in the fuse box.

After some thinking...

My guess is that a PO at some point replaced the radiator and fans with the early model single fan and radiator, either because they did not understand the differences, or they could not find a good used late model radiator. They then wired the early two pin thermo switch to the slow speed input on your late model three pin fan relay (probably with some custom wiring), causing the single fan to run only in slow (or high) mode.

This is probably not enough to keep your car from overheating while in standing still or in traffic, as the late model cars need two fans running in either slow or high speed mode (high speed = AC running or coolant temp above 102C). If my theory is correct, right now you have one fan in one speed (high or low) mode only.

Recommend changing the radiator+fan setup to the correct late model dual fan setup, install the correct 3 pin thermo fan switch (likely already installed on the late model radiator if you get one used) and wire up accordingly to your existing (assuming late model) fan relay, as it should have been from the factory. The high/low speed pinout of the late model thermo switch is on Clarks and should give you the basis to connect the correct wiring to the fan relay:


Also, there are multiple different thermo fan switches with different temperature activation points. You must be sure that these are higher temps than what your thermostat is set at or your fans will run all the time. Clarks notes the normal thermo switch (again, late model 3 pin) high low temps are 92C and 102C. If you go with a used radiator this is likely already installed, but you still may want to double check. The temps should be stamped on the brass casing of the thermo fan switch itself.

Can you confirm whether there is custom wiring coming out of the two pin thermo switch on the radiator going to the fan relay (meaning there is no OEM plug, or an OEM plug with wires spliced)? If this is the case then it confirms the PO installed the wrong cooling fan/radiator setup for your car... You will also want to double check the wiring to the fans and see if the wiring for the second fan is clipped or tucked away somewhere.

[Evil Dan]

Originally Posted by walfreyydo

After some thinking...

My guess is that a PO at some point replaced the radiator and fans with the early model single fan and radiator, either because they did not understand the differences, or they could not find a good used late model radiator. They then wired the early two pin thermo switch to the slow speed input on your late model three pin fan relay (probably with some custom wiring), causing the single fan to run only in slow (or high) mode.

This is probably not enough to keep your car from overheating while in standing still or in traffic, as the late model cars need two fans running in either slow or high speed mode (high speed = AC running or coolant temp above 102C). If my theory is correct, right now you have one fan in one speed (high or low) mode only.

Recommend changing the radiator+fan setup to the correct late model dual fan setup, install the correct 3 pin thermo fan switch (likely already installed on the late model radiator if you get one used) and wire up accordingly to your existing (assuming late model) fan relay, as it should have been from the factory. The high/low speed pinout of the late model thermo switch is on Clarks and should give you the basis to connect the correct wiring to the fan relay:


Also, there are multiple different thermo fan switches with different temperature activation points. You must be sure that these are higher temps than what your thermostat is set at or your fans will run all the time. Clarks notes the normal thermo switch (again, late model 3 pin) high low temps are 92C and 102C. If you go with a used radiator this is likely already installed, but you still may want to double check. The temps should be stamped on the brass casing of the thermo fan switch itself.

Can you confirm whether there is custom wiring coming out of the two pin thermo switch on the radiator going to the fan relay (meaning there is no OEM plug, or an OEM plug with wires spliced)? If this is the case then it confirms the PO installed the wrong cooling fan/radiator setup for your car... You will also want to double check the wiring to the fans and see if the wiring for the second fan is clipped or tucked away somewhere.

Its all factory wiring, I'm assuming the 87S UK spec was a odd ball.
Like I said in the original post the fan works on high when driving and then slow speed when the ignition is off but the temp is still high.

What I need to know is do the 2 fans run on the same circuit are do they have an individual power source from the relay? Do both fans run high and both run slow when required or are they switched independantly?

Thanks

Dan




What I need to know is do both fans come on high

[walfreyydo]

With a dual fan setup on the late model cars, both fans run on low when temp is between 92-102. Both fans run on high when above 102C or when AC is running (this is all explained on the Clarks garage page I posted above). There is no individual control for each fan (ie: one runs on high one runs on low).

I believe both fans are controlled/powered through the fan relay, which switches low/high based on the reading from the 3 pin thermo fan switch in the radiator or the AC. Actual fan speed is controlled through the fan resistor.

Wiring diagrams are available in the link I posted above if you want to dig in.

[Monkey Wrench]

in volvos of the same era it is common to install a heater fan with more windings and an updated switch. It'll then use winding 1 , 2 or both to change speeds.

it sounds like Porsche only used a 1 speed motor in the 944 ( rad fan not heater blower motor) but perhaps later models or updates could use a motor with more choices of field windings rather than adding power wasting resistors in series to slow the motor which is essentially electrically inefficient. .

the 1 speed motor might be slowed by switching in a resistor in series.. power after the resistor will be less than 12V due to the power drop through the resistor so the slower speed is the motor basically running at less than 12V .


a motor with more windings may not need a resistor to change speeds , they may use 1 2 or both windings to get the three speeds and then no resistor is needed.

I think that similar to the rad , the resistor is basically a very inefficient device, it's sole purpose in life is to waste energy. Perhaps it is possible to upgrade a fan motor if the amp draw is of particular concern.

Best advice is probably to follow Clark's garage notes and keep it OEM.

Liverpool has similar weather to BC. Its not like the southern US, I wonder if Porsche realized that colder climates dont need AC or that extra fan.. perhaps that meant different options from the factory by region?

adding or deleting AC may have never been a dealer task, they were probably only sold as built in the factory.

I did not notice an option code on mine for AC.

[J1NX3D]

Originally Posted by walfreyydo

Only true on early model cars according to Clarks - but maybe thats for USA models only?

My NZ-market RHD '86 was no A/C from the factory and exactly the same single fan set up as the OP has described about his 944S. It threw me when I bought a 3 pin thermo switch for a late 944 and realised I couldn't use it.

Non-A/C 944 all seem to have single fans, US cars all seem to be spec'ed with A/C so always had 2 fans...?

Our single fan 944's also have a different cooling fan relay so those SS ones that F9T sell for example are no good to us.

Below are internal pictures of the new F9T Solid-State Cooling Fan Relay next to various original mechanical cooling fan relays. As you can see, the “Cooling Fan Relay” actually has several “internal relays.” Each fan has a dedicated relay for low-speed and high-speed operation. However, the earlier versions have a fifth internal “control” relay that was later replaced with numerous electronic components. The factory went through several updates to the dual fan relay with the latest version being “04.” Obviously, the F9T relay takes a more modern approach. The mechanical relays are replaced with four independent “smart” power switches. These power switches are designed to drive inductive loads such as automotive cooling fans or smaller starter motors.

This is mine

[walfreyydo]

Great info on the ROW cars, thanks for sharing. I do believe all US late model cars had AC

I do see in your photos background that you have a 968 (or is that a 968 engine installed in a 944?)

[J1NX3D]

Yes, a 944 with a 968 'S3' conversion. I've done a quick and dirty update on my Garage for some details, i've probably forgotten something.
J1NX3D's Garage :: J1nx3d my IG is kiwi944s3 if you use it.

Like the OP, I'm considering going to a dual fan set up too.

[v2rocket_aka944]

if you have access to any breakers near you, see if you can find the fan relay unit for a 1990s-early00s Volvo 850/V70.

you need 1 big power wire in (alternator + post is a good place), and two switch inputs (your factory 3-pin fan switch will do), and there are two output wires - high speed and low speed.

if you split each of those output wires to run 2 fans instead of one, you should be golden.

i have one of these Volvo relays, controlled by a 944 switch, in my car (but running the Volvo's large single fan on a non-stock radiator)

[Monkey Wrench]

If overloading the original OEM relay by the addition of a second fan that never existed, is a concern you could simply use the relay to switch a second larger relay ( rated for more ohms) and then the OEM one would only see the current to run the coil of that relay. That's just basically daisy chaining the relays to prevent an overload on the OEM's relay contacts.

the way it "should" be wired for the two fan system seems a bit more complicated, maybe it reduces noise by not running the second fan when not really needed and maybe that does a better job of regulating the temperature.