urquattro20Vt

Hey guys-
'1991 964 Turbo.
Ok so weird things happening. Two things actually - I wonder if related? (EDIT - I do think they are now).
First - turn key on, but not all the way to start - there is a weird vibrating metallic rumbling noise - like super unhappy bearings - coming from passenger/right rear corner area, possibly closer to the rear wheel?. Like some pump is super unhappy??? Engine not running so not power steering. Noise is located more outside/back from there anyway - I think. Noise continues after engine running - but eventually quiets down. What else is back there??

Maybe coincidentally - I had my CCU rebuilt by Specialized ECU a few years ago. Several times now (especially in the last week - even more so today - very consistent today) I've turned the car on and the HVAC fan comes on - like Speed 3. Will not obey input from the fan speed dial. And the oil cooler fan comes on and the AC condenser fan. Turn car off everything (all fans AND the unhappy "pump") continues to run while the CCU fan runs for about 20 seconds - then everything turns off. I can now start the car without all the fans coming on. If I turn the ignition back off before going through this process all the fan come on as I turn the key to "on". and back on and all back to normal.

I will contact Specialized ECU this week - but anybody had this issue?

Brandon
​​​​​​​'91 Turbo

ToreB

I guess one or both of your electric fans in the engine compartment has given up the ghost. The bearings fail, and the fan cage creates havoc when crashing into the fan housing. It is impossible to determine the cause for noise without being able to inspect the car.
It sems you have an issue with the CCU indeed, the fans shall not behave like this, and I cannot see how an external fault should cause this. I assume your service vendor can help.
Cheers,
Tore

No_snivelling

It does sound like bad fan bearings. I had my rear blower turning on (speed2) when it should not and fixed it by replacing the ballast resistor and the thermister.

systemsc

The 964/993 CCU is very reliable and rarely fails in its original factory condition. Read here under Porsche/CCU 964/993; https://www.systemsc.com/problems.htm

urquattro20Vt

yeah I bet its the blower motor bearing dying.

Cold start today none of this stuff happened.

Would the CCU know something weird is going on back there - and it's causing it to run all the other fans (oil cooler, AC condenser, cabin blower)??

Brandon
'91 964 Turbo

peterpullin

only thing you can read out is klimate and abs i think. no more options on our cars.

only standard 964 have access to all systems via obd. turbos are oldschool…

ToreB

As mentioned above, it sems you have an issue with the CCU indeed, the fans shall not behave like this, and I cannot see how an external fault should cause this.
Cheers,
Tore

pretarch

Brandon, call Specialized ECU Repair, they are really good at taking care of warranties on these CCUs.

Lorenfb

It's good that you, (pretarch AKA - Specialized ECU Repair/ECU Doctors), are in involved in resolving your warranty issue with the OP.

Metal Guru

Ahh, not a paying sponsor I recon.

Metal Guru

Thought I read somewhere that the CIS frequency valve can be monitored, but that's about it.

systemsc

That part is used on a 911SC, which doesn't have a diagnostic system like the 964 and later Porsches.

Metal Guru

The 964 Turbo uses CIS.

systemsc

Right, but there's no diagnostic system for the 965.

Metal Guru

Per the Bentley manual, diagnostics accessible thru the Bosch Hammer on the 964 Turbo include:
*Oxygen sensor control unit
*Turbocharger control unit
*Acceleration enrichment control unit
*Ignition control unit
*Airbag system