Cupcar#12

need some help (scratching my head actually)

some questions...
Does G12 have current normally - it does not have anything that i can detect.

My switch is installed and the fan works when jumpered? but the override does not work and i cannot get it turned on without jumping it.

the CCU works fine for Ventilation control.

any ideas?

Cupcar#12

Bad Relay?
I jumpered both high and low speed operation and that works so the resistor is fine.
the odd thing is i have power on term 86 and nothing on 30 - possible mis wire in the central electrics connector?

C4Russ

Rob, how long do you wait for the fan to kick on? The switch isn't instant. It takes a moment for the CCU to think about it before turning on the fan.

Cupcar#12

a minute or two - does it take longer than that?

C4Russ

I don't think so, mine starts in 30-50 seconds. I was hoping for something simple.

Tom W

Mine starts immediately (in the 993).

I found in the 964 that it was best to completely remove the fans. I get much better air flow without the fans and, with dual coolers, my oil temps stay at about 180-200 °F, even when the track temp is 100 °F or more.

Cupcar#12

Mine Seems to run hotter with the fan (not running)

worse comes to worse i can jumper it - i have a new relay on order and will test the temp control switch tonight

JasonAndreas

No

The oil cooler temperature sensor is NTC (negative temperature coefficient) based so to get a reading you measure resistance between pins G12 (Sensor) and G18 (Ground). Ambient would be somewhere between 4 and 5 k-Ohms.

Cupcar#12

ok good to know then.

The fan does not come on when the temp sender is unplugged - hopefully this means the relay is bad.
correct me if i am wrong here

Cupcar#12

More questions -
New relay - found that the #2 Fuse (30a) was blown and replaced -
Fan works But.......

it is locked in high - so Open Circuit basically defaulting to HIGH operation.
When i measure resistance across G12 & G1 i am in the 19K range - but when i measure it on the T14 connector in the trunk i am at 0.


So my new question - i cut the G12 wire to install a switch - however even with the wire reconnected with nothing in between i am at 19k

i checked the temp switch (it is new) last night

The resistor passes the jumper test for high and low.

so now what? any idea's?
Replace the Temp sender?

tbennett017

Additional question: I want to experiment with running the fan at a lower initial temp. Does anyone know of a different temp sender unit calibrated at a lower temp setting? I could hardwire it.. but I would rather have it be automatic...

thx.

Cupcar#12

further update on my issue.

1) the hammer reports temp sender ground fault (sender is new and plugged in - Any ideas Guru's?????
2) replaced the wire leading to G12
3) replaced temp sender and resistor

still stuck on high - gone to try a thing or 2 more but basically i at a fault stage i can live with.

Cupcar#12

further update on my issue.

1) the hammer reports temp sender ground fault (sender is new and plugged in - Any ideas Guru's?????
2) replaced the wire leading to G12
3) replaced temp sender and resistor

still stuck on high - gone to try a thing or 2 more but basically i at a fault stage i can live with.

JasonAndreas

That is the way the fan switch is supposed to operate. If the CCU detects a temperature sensor fault the oil cooler fan is operated in high speed mode. The switch is supposed to break the circuit.

Are you checking between G12 & G1 or G12 & G18? The measurement should be taken between G12 & G18 and from the larger of the two connectors (the upper one) on the back of the CCU. Also, the trunk connector that you want to check is T34 and not T14. Do you have a hammer or did you just borrow one?

Cupcar#12

thanks - just borrowed the hammer - my local shop is very helpful
i will double check the ohm reading tonight.
but either way it is reading an open circuit - so the fan comes on - i tried bypassing grnd on the sender to a known good ground - no change, fan on high and circuit open.
i am starting to think the pos is not connected on the switch or i have some other wiring issue.