nine9six

About a week ago the fan on the oil cooler would come on and run constantly, with the key turned to the III position, just before actuator in the starter, and it runs consistently while the car is running.

In connecting the PIWIS, I got error codes in the Heating/AC, module block, indicating errors, 16 and 21; outside air temperature sensor and oil temperature sensor, respectively. I have purchased and installed a new oil temperature sensor and a new outside air temperature sensor, however the same issue persists...

Has anyone had a similar/same experience, that has since fixed this issue? I am now beginning to think this may be more related to the CCU, since sensor replacement did nothing and the error messages still persist on the PIWIS.

I did find this link...
https://rennlist.com/forums/993-foru...re-sensor.html

EDIT
... and did more reading and research now I'm thinking possibly the oil temperature fan resistor...

TIA

ToreB

Just throwing in new parts may not be the best approach to solve problems.
I would recommend to use the OBD tool to read out the sensor values, especially the Climate Control Unit oil temperature sensor. Are the readings OK?
Did you delete the fault codes after sensor change, and did the codes reappear?
Are the other CCU functions working, such as heat regulation and the two slider controls?
Cheers,
Tore

Floodj

If you do replace the CCU, you might check out these guys.
http://www.ecudoctors.com/

I honestly know nothing about them, but I do know what they are saying makes sense.

ToreB

A failing oil cooler low speed resistor will not make the fan motor run continuously. However, it is very easy to test the resistor, see this DIY procedure.

There is no need to replace the CCU in this case, if it is an internal fault, it can be repaired at a much lower cost than a replacement.
Cheers,
Tore

Lorenfb

And what is being said that makes sense?

nine9six

Thank you for chiming in, Tore...I had hoped you would...

As originally stated, the oil cooler fan runs at high speed continuously with the ignition key in the III position even when the motor is cold, at initial startup of the day.

UPDATE

In checking the CCU operation, Max Air works intermittently and will start again if the sliders are moved back and forth...

P.S. A year ago, I purchased a new, in series oil cooler resistor, (993 616 521 01) from a Rennlister who had sold his 993. Because my car is 23 years old and I am already in there with the oil cooler, should I not go ahead and installed the new resistor?

Paul

ToreB

The oil temp sensor shall show room/ambient temperature when the engine is cold, moving up to 60-100 degrees C at hot engine. The outside temp sensor value should be...

I suggest to test all HVAC servos. If they do not work, you probably have a fault in the Sensor GND circuit internally in the CCU, affecting all sensor readings and servo position feedback. The most common cause for such a fault is a short circuit in the engine compartment wiring loom. Has your car had the engine wiring loom replaced under warranty?

Cheers,
Tore

nine9six

Yes, under the previous ownership, with the updated loom.

nine9six

Tore,
Would such a gnd short prevent the fan from operating at temp?
TIA

Lorenfb

Extremely rare! If that were the case, most all functions of the CCU would be inoperable.

ToreB

Loren, I do not agree with you, I see this fault often enough to say that it is a common fault.

As mentioned in my post #7 above, a fault in this circuit will make it impossible to measure any CCU sensor, and all the HVAC servo motors will not move. However, the control of the two main blowers will still work.
It may well be that some time in the past, +12V has been introduced to the Sensor GND circuit due to a faulty engine wiring loom. I also have seen this if the rear temp sensor connector in the engine bay has been wrongly connected to someting else.
This causes permanent damage to this circuit internally in the CCU, but the user may be unaware of the inoperable functions if there's no need for temperature regulation, or just by ignorance.
Cheers,
Tore

Lorenfb

To check the CCU for a corrupted ground/grounds, one just needs to check the continuity between G18 (G-35 pins) signals ground, & K1 (K-25 pins) main ground.
Also, one needs to all always check for three powers, #30 (K2), #15 (G35), X (G29), and making sure no pins of either connector have come loose while removing the CCU.

nine9six

FWIW, the oil cooler fan was operating fine until about a month ago when came on when the key was turned to position lll, and the car was stone cold.

The PIWIS reported errors 16, and 21 with outside air temp, & oil cooler temp sensors. I have since replaced both sensors, yet the errors still persist even after erasing them with the PIWIS.

I jumped contacts in the RO4 relay, to test both the low and high speed fan operation and both operated as expected.

https://www.pelicanparts.com/techart...ubleshoot2.htm

Admittedly, I am significantly more mechanically inclined whereas I would describe myself as electronically stunted.
; )