overheating 944S 16v

[onrails]

so, im in the same boat of overheating, ive read this thread and have followed clark's. third cooling fan thermo switch finally from Porsche dealer. New to me off ebay, ceramic resistors, replaced and tested fans, relay circuit tested as described in clark's ok high and low. I am not sure of the placement of wirers to the resistors, ive been chasing this for a while now. I have a BLK/RED, RED/BLK, RED/WHT, and RED/GRN. This is a 944 "S" and i can not find the exact color wire placement to the resistors. The black w/red stripe isnt a option that i have found. Hopefully there is an "S" model enthusiast that can afford some advice.

[walfreyydo]

Some more information would be helpful.

When does the car begin to overheat? While moving or while sitting still?

Have you confirmed the fans are not coming on when your temp gauge reaches the second mark (90C)?

I have an 89 S2 and can take a photo of my resistors and post back so you can see the wire colors - if that would help.

[TibetanT]

Hello There:

I have a 1987 944S, is that the year you have?

First and foremost, any records of work done to the vehicle up to this point?
Second, how did you get to the conclusion that the wiring to the resistors are not correct?

I am confused as to what the actual question regarding overheating is, so that's why I am asking. Do the fans come on at all? When driving, does the temp gauge go above the third "line" indicator on the temp gauge or does it go all the way into the RED?

Also, when was the last time the water pump and thermostat was changed? <
Also, are there any hoses leaking within the engine compartment?

If you need some pictures of what my 1987 944S wiring to those resistors look like, let me know and I will take some pictures to try and help.

Good luck with your investigation.

[onrails]

87' 944S
I have owned and worked on it for 20+ years.
Replaced: water pump new style; thermostat twice 83c; thermo switch three times, Advanced Auto, Amazon, last one from Porsche dealer; resistors off Ebay process of elimination.
Work done: resistor wire repair, same gage wire; reservoir and cap tested; thermostat tested in boiling water; relay test per Clark's; high/low speed fans per Clark's; AC button fans per Clark's, all fan tests passed with jumper; tested water pump is pumping with garden hose in reservoir and no thermostat upper hose off; Compression tested all 4 cylinders 180+; I have questioned the thermo switch BUT 3 of them? I have not had success testing it as Clark's has limited info on the S model.
Driving it with no thermostat it stays around the first line(bottom); at idle it will eventually go to red with no fans coming on until I hit the AC then fans on and it cools fast. I have messed with the resistor wires so much it would be nice to have a pic or diagram to eliminate that as well. Heater works and engine runs strong with no timing or mechanical issues. This may be a repost as the first one said i timed out.

[originalowner]

Do both fans come on when you turn on the A/C, or just one?

[jjeffries]

Are you doing anything to corroborate what the temperature gauge is telling you, as in, using a thermometer of some sort to measure coolant temps?

John

[TibetanT]

Onrails:

Sorry for the delay with getting back here, but right now my garage is at 9degrees, so too cold for me.
My engine cowl cover will crack and break if I try to remove it for pictures right now.

I will get information as soon as I can.

The switch you speak of, is this the fan switch on the radiator? Or is it the switch on the engine block?

I always try to ensure my fan switch on the radiator is of the same degrees Celcius as the thermostat used within the water pump. <

[TibetanT]

Onrails:

Unable to get the pictures, so I used a small mirror and a good light to see what the wiring is for the resistors.

Nearest to the passenger side of car, the wiring is : Top Brown/Red Bottom Black/Red

Nearest to the center of engine side, the wiring is : Top Red/White Bottom Red/Green


Hope this helps, and good luck!

[onrails]

Originally Posted by originalowner

Do both fans come on when you turn on the A/C, or just one?

Both

[onrails]

Tibetan T

Fan switch on radiator and thermostat from Porsche dealer, 83 degrees Celsius. I did find that the RD/WH and RD/GN were wrong. The other 2 are BK/RD and RD/BK. I will test this combo. Thanks for the help. Sorry for your weather, I spent many years in Alaska and know how it can get.

[onrails]

Both

[originalowner]

Originally Posted by onrails

Work done: ... relay test per Clark's;

If you have successfully passed the 9 steps in Clark's titled


Testing Late Model Cooling Fan Relay


Then the thermo-switch on the radiator is bad or not getting hot. You can test the operation of the low-temperature (slow-speed) contact by measuring the resistance of the switch with the sensing end in boiling water. It should close like a switch. The high temperature contact closes above the boiling point of water, making it more difficult to check. Start with the slow-speed, as that part is not working for sure.

Originally Posted by onrails

I have not had success testing it as Clark's has limited info on the S model.

The S is the same as the other versions with respect to the cooling fans.

[onrails]

I am doing those steps now. I did purchase a relay because my thermo-switch is from the dealer. I will definitely start with the low-speed contacts when I test it. I will keep Ya'll posted.

[onrails]

did the boiling water test on one of the many thermo-switches i have replaced,.. no contact.. after replacing the relay(fuse/relay), i have high speed fans when it gets near the red. still no low speed. so im really looking into the low speed wiring to the resistor? I need more diagrams as this "S" model still uses the turbo parts/part#. Help?

[onrails]

my infrared temp gage shows 175F but i will never trust it from the waterpump.

[onrails]

what are these 3 wires at the power steering pump that i was told to disconnect years ago?

[djnolan]

should you be able to jumper the thermofan switch wiring to check the low speed fans?

[944 Ecology]

Originally Posted by onrails

what are these 3 wires at the power steering pump that i was told to disconnect years ago?

Those two wires are an unfused circuit (connected to a pressure sensor in the pump) designed to boost the idle speed when the steering is cranked all the way left or right. Instead of working as designed, it ended up burning very expensive wiring harnesses.

[originalowner]

Schematic:

[onrails]

I hear what you are saying about the temp censor, but the high speed turns on when VERY hot can I deduct that it is receiving a HOT coolant message, meaning it is sensing the coolant? Bringing me back to the low side of the thermofan switch itself? They do turn on slow speed when jumped at the harness/plug. Definitely getting frustrating after 2 aftermarket and the 3rd switch ordered from Porsche Dealer.