phoneyman

I have been searching through the archives for the last 2 hours, and have learned a lot about the 993, but not enough to fix my problem:

Short: Disconnected battery to install some things, reconnected battery. After turning ignition on (not starting car), the rear blower motor stays on forever (ignition off) until I disconnect battery.

Long: I disconnected the battery to swap out Momo steering wheel with a 996 GT3 wheel. Got the wheel installed, connected battery and turned ignition to on to test horn. Everythings fine. Disconnect battery again to rewire stereo (swap switched and constant 12V+ on Crutchfield harness), put radio back in the DIN slot and reconnected battery. Turn ignition on, and the rear blower fan starts at the low speed. Turn ignition off and fan blows until I disconnect battery. I have:

1) Turned the CCU temp all the way down as stated in an old thread, no change.
2) Checked the rear blower relay, everything seems to check out. Terminals 30c, 87c & 30, 87 are disconnected, 85, 85c, 86 are connected. no change.
3) Checked that the radio did not disconnect connections on back of CCU. no change.
4) Disconnected battery for ~1hr and reconnected to see if something needed a hard reset, no change.

The CCU is making an electrical hum while blower motor is on and key is out of the ignition. I'm thinking the CCU is the next place to look? Anybody have another place to start snooping around?

TIA

JB 911

Did you try tapping the rear relay in back fuse panel? (to see if it has stuck)

Did you try swapping it with one of the front relays from the ac condenser or oil fan ? I think they are the same.

That would probably be too ironic though to have a relay fail at the same time you did a repair. I'm thinking something got knocked loose.

phoneyman

I have not tried either of those ideas, but I will. I imagine the relay is not stuck as the continuity check implied the switches were not on. I will read the bentley and check that the two relays are the same and if so swap. I felt around the back of the CCU and the connections seemed firm, but will check again and possibly pull the CCU.

Just tried again and this time the front fan(s) (condenser or oil cooler) also turned on with ignition and cycled on and off a few times. This is so confusing.

JB 911

double check the battery cables are tight and that the battery ground strap didn't get knocked loose

phoneyman

Connections are tight and the ground strap wasnt knocked loose. I disconnected the (+) side both times instead of (-)/ground accidentally. Could that cause problems?

phoneyman

Just wanted to add this to the thread in case someone wanders on it in the future. I found an old post by Randall G (thanks!) that states the resistance values that the air temperature sensor in the rear blower motor should read, as per the shop manual. I am going to check those pieces next as the relay is good and the CCU "seems" good.

https://rennlist.com/forums/94651-post27.html

ToreB

You might have a internal problem in the CCU preventing it from shutting off after ignition off. This can be the known problem of a transistor fail. The hum you hear is probably from the CCU fan.
I've described details in this here:http://www.bergvillfx.com/ccurepair.html
Cheers,
Tore

Garth S

Why not go back and delete/reverse the swap of unswitched (buss #30) to switched ( either X-buss or #15 buss) ....and see what happens.

It may be that you have introduced +12V into the trigger side of certain relays ( 86 -> #85): regardless, I do not know specifically the goal of the 12V feed swap, but would use that as a "restore" point

techman1

Try temporarily undoing the wiring for the Crutchfield adapter, (swap switched and constant 12V+ on Crutchfield harness), and see if the issue is corrected.
Sounds like a relay is being energized through an indirect feed. Also look very carefully at wire sheathing behind the radio for a pinched wire.

phoneyman

Tore, Ive read every word of your site for the CCU/HVAC related stuff. I have a couple small things to try first, and if they dont work I will pull the CCU and diagnose from your awesomely informative site. Thanks.

phoneyman

The first thing I did was disconnect the radio completely and remove it from the equation. With the open terminals and knowing nothing is bridged inside the adapter housing, that should eliminate the radio as the problem. The goal of the swap was that the Crutchfield harness has switched and constant 12V+ swapped on their harness so my radio could not hold its settings. Thanks.

phoneyman

Unless swapping relays and checking the rear air temperature sensor work, I will be pulling out the CCU and checking all the wiring sheathes. Hopefully its something simple and not something inside the CCU.

techman1

Some wiring adapter plugs from Crutchfield had internal connections (bridges), for example power in #2 supplied connection to out 2 & 4.

Just making a WAG, goodluck!

phoneyman

Thats good to know. I guess I didnt check very thoroughly.

As for the problem, it solved itself. I left the battery disconnected overnight, charged it disconnected from the car for a few hours, and everything is functioning properly. Cycled through the CCU to make sure the fans turned on at the right times, the rear aux blower turns off at the correct time, etc. So I guess it was a non-issue. Not sure what caused the kwirk, but seems to be no problem. Thanks to everyone for the advice.

phoneyman

Do the blinking lights for the security system tell you anything about problems? I know that if a sensor is tripped, the lights blink twice real quick. Now when I lock the doors with everything shut, the lights blink about 2/second for ~10 blinks, then settle to the normal blinking pattern. I'm searching the archives and looking for my manual in a box to see if this is normal.

lopro suggested that maybe I have a current drain somewhere, so wanted to check if the security lights are an indicator people know about. TIA