groovzilla

all,

i noticed last night a static interference noise comming from the CCU during and AFTER i turned the ignition off.

the sound was gone this morning but when i started the car i got the same noise, turned off the car and the noise went away within 10 seconds.

i started car again and the noise started up again and this time it would go away after the ignition was turned off...i fianlly disconected the battery the noise stopped...i did notice a spark when i removed the negative ground at the battery so there is something up with the CCU>>

any ideas???...

again its not a motor sound it is a radio static sort of noise..

thanks

John Boggiano

In spite of how you described it, could it not be the tick-tick-tick of the little fan fouling its casing?

You know that that fan runs for twenty minutes after you turn off the ignition, UNLESS the ignition was only on for a few seconds?

groovzilla

the CCU fan runs after the ignition is turned off even if the fan control is turned to the OFF position?

KirkF

After the ignition is turned off, a small fan in the back of the CCU continues to run for 20 minutes.
The purpose of the fan is to move cabin air over the internal temperature sensor in the CCU.

I'm not sure why they choose to keep it running after ignition off. Maybe to ensure no overheating occurs in the CCU.

The fan is a common source of 964 power drain. A transistor fails in the circuitry, and it leaves the fan on forever.

Kirk

John Boggiano

I think it's tied in with the circuit that monitors post-shutdown engine temperature and activates the rear blower to cool it if necessary - that's why it runs on after ignition off.