ccu complete failure - why
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Joined: Jun 2006
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From: Cambridge, United Kingdom
ccu complete failure - why
heater temp stuck on hot, all fans ceased working - ccu help
Hi guys,
All the fans have stopped working on my car all at the same time.
No heater fan, no aircon, no windscreen demist - everything suddenly stopped working. even the oil cooler blower under the front wing (which has been a problem because it is always on full) has stopped.
I'm assuming its the ccu - but I've checked the fuse for the ccu unit and it seems fine.
Any suggestions on why the whole unit would suddenly fail and how to fix it will be gratefully received.
Thanks
Marc
Hi guys,
All the fans have stopped working on my car all at the same time.
No heater fan, no aircon, no windscreen demist - everything suddenly stopped working. even the oil cooler blower under the front wing (which has been a problem because it is always on full) has stopped.
I'm assuming its the ccu - but I've checked the fuse for the ccu unit and it seems fine.
Any suggestions on why the whole unit would suddenly fail and how to fix it will be gratefully received.
Thanks
Marc
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Joined: Sep 2009
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Hopefully expert Tore will pick up on this thread soon.
No expert here, but unusual for the entire unit to crash I think.
They tend to fail with no real pattern, dropping off signals to a servo or two, then losing control of fan speed....
I posted a week ago looking for feedback on an outfit advertising rebuilds for $375 on ebay....no response.
New CCU's seem to cost $1500 or more.
Gordo
No expert here, but unusual for the entire unit to crash I think.
They tend to fail with no real pattern, dropping off signals to a servo or two, then losing control of fan speed....
I posted a week ago looking for feedback on an outfit advertising rebuilds for $375 on ebay....no response.
New CCU's seem to cost $1500 or more.
Gordo
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From: Canada & the Alps
Are you comfortable taking measurements with a DMM? If so, I can e-mail you electrical schematics.
I just got off an AC troubleshooting exercise. You need accurate data to come up with the right fix. As soon as I got that, a 20 cent diode in the AC Compressor relay was all it took for the fix.
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^Specialized ECU Repair out of FL. They only work on 95' and older ECU's. Gremlins scare me.
WWW.PorscheDME.com-(800)328-1425
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Joined: Apr 2004
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From: Oslo, Norway
I'd start with checking two fuses (28 and 17), then check the power supply leads to the CCU.
Pull the unit, and use a voltmeter. Connect voltmeter GND to pin K1 (brown wire)
Voltmeter plus lead to pin K2, (should be +12V permanent)
G29, (ignition switched +12V)
G35, (ignition switched +12V)
Details on the connectors and more here.
Cheers,
Tore
Pull the unit, and use a voltmeter. Connect voltmeter GND to pin K1 (brown wire)
Voltmeter plus lead to pin K2, (should be +12V permanent)
G29, (ignition switched +12V)
G35, (ignition switched +12V)
Details on the connectors and more here.
Cheers,
Tore
Thread Starter
Advanced
Joined: Jun 2006
Posts: 68
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From: Cambridge, United Kingdom
I'd start with checking two fuses (28 and 17), then check the power supply leads to the CCU.
Pull the unit, and use a voltmeter. Connect voltmeter GND to pin K1 (brown wire)
Voltmeter plus lead to pin K2, (should be +12V permanent)
G29, (ignition switched +12V)
G35, (ignition switched +12V)
Details on the connectors and more here.
Cheers,
Tore
Pull the unit, and use a voltmeter. Connect voltmeter GND to pin K1 (brown wire)
Voltmeter plus lead to pin K2, (should be +12V permanent)
G29, (ignition switched +12V)
G35, (ignition switched +12V)
Details on the connectors and more here.
Cheers,
Tore
I checked fuse 28 yesterday which was fine but not 17. Will pursue that avenue this evening and then pull the unit as you suggest. Do I need to disconnect the plugs from the unit to test the connections (ie am I able to get the voltmeter test by sticking the prongs in the back of the plug)? I ask because I pulled the unit once before and found it difficult to unplug the two big connectors in the space availaable and did not want to do any damage.
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Joined: Apr 2004
Posts: 2,570
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From: Oslo, Norway
Measure them with the plugs inserted. Just stick the probes in where the wires go.
I agree, it's a pain to get the plugs out, I use a small screwdriver as jack on the clip side, if you understand what I mean. (press the retaining clip, and lift the plug with the screwdriver)
OK power supplies suggests some internal CCU fault. It could be anything, shorts, defective CPU and so on. Could be repairable or not. Cross your fingers...
Cheers,
Tore
I agree, it's a pain to get the plugs out, I use a small screwdriver as jack on the clip side, if you understand what I mean. (press the retaining clip, and lift the plug with the screwdriver)
OK power supplies suggests some internal CCU fault. It could be anything, shorts, defective CPU and so on. Could be repairable or not. Cross your fingers...
Cheers,
Tore
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Thread Starter
Advanced
Joined: Jun 2006
Posts: 68
Likes: 0
From: Cambridge, United Kingdom
I'd start with checking two fuses (28 and 17), then check the power supply leads to the CCU.
Pull the unit, and use a voltmeter. Connect voltmeter GND to pin K1 (brown wire)
Voltmeter plus lead to pin K2, (should be +12V permanent)
G29, (ignition switched +12V)
G35, (ignition switched +12V)
Details on the connectors and more here.
Cheers,
Tore
Pull the unit, and use a voltmeter. Connect voltmeter GND to pin K1 (brown wire)
Voltmeter plus lead to pin K2, (should be +12V permanent)
G29, (ignition switched +12V)
G35, (ignition switched +12V)
Details on the connectors and more here.
Cheers,
Tore
Progress - there is no 12v power at pin K2 (red wire), either with or without the ignition on. Will this be the cause? Where do I go from here?
fyi both fuses 28 & 17 test as ok and both pins G29 & G35 show 12v when ignition is on
Marc
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Joined: Apr 2004
Posts: 2,570
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From: Oslo, Norway
Spot on! Red wire , K2 is Terminal 30, a name for permanent +12V, Fuse 1. It's a 25A fuse, if it's blown there's a reason for it. I'd bet there's an obstruction or short in one of the front blower motors.
Cheers,
Tore
Cheers,
Tore
Thread Starter
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Joined: Jun 2006
Posts: 68
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From: Cambridge, United Kingdom
I replaced Fuse 1, reconnected the ccu and it started functioning ok. Turned interior fan to position 1 and could hear both left and right fans running. position 2 - still ok. Position 3 and the left hand fan motor started whining then everything stopped. Fuse 1 had again blown.
Have replaced the fuse again and the ccu/heater etc all work fine if I don't move beyond fan position 2.
Any tips for what i should do about the left hand fan?
thanks again.
Marc
Last edited by a993lad; Aug 24, 2012 at 03:49 PM.
Rennlist Member
Joined: Apr 2004
Posts: 2,570
Likes: 538
From: Oslo, Norway
Good job!
I'm afraid you have to change the fan motor, the bearings are probably shot. A fairly large job, and ridiciously high spare part price. Do a search on the forum for front blower and you'll find a lot of information on this, both in the 964 and 993 forum.
While waiting for the money to have it done or the guts to do the job yourself, you could disconnect the motor in question by removing the brown/red wire from the Blower Final Stage connector harness. The final stage is placed behind the fuse box in the trunk, under the thin plastic cover. It's got a long narrow connector on top. I've never tried to remove wires from that harness, but would expect the pins to be held by clips or something. No. 5 in my picture here:
http://privat.bluezone.no/toreb2000/...vooverview.JPG
Good luck, and cheers,
Tore
I'm afraid you have to change the fan motor, the bearings are probably shot. A fairly large job, and ridiciously high spare part price. Do a search on the forum for front blower and you'll find a lot of information on this, both in the 964 and 993 forum.
While waiting for the money to have it done or the guts to do the job yourself, you could disconnect the motor in question by removing the brown/red wire from the Blower Final Stage connector harness. The final stage is placed behind the fuse box in the trunk, under the thin plastic cover. It's got a long narrow connector on top. I've never tried to remove wires from that harness, but would expect the pins to be held by clips or something. No. 5 in my picture here:
http://privat.bluezone.no/toreb2000/...vooverview.JPG
Good luck, and cheers,
Tore
Racer
Joined: Sep 2006
Posts: 437
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From: Auckland NZ & Newcastle AU
Here is my budget solution for replacing the right side blower motor, as posted on the 964 forum recently -
https://rennlist.com/forums/9761099-post9.html
If anyone is pulling their left blower out for a repair, could you kindly post the Bosch part number on the motor? That'd help to see if we can also source a cheaper blower motor replacement for the left.
https://rennlist.com/forums/9761099-post9.html
If anyone is pulling their left blower out for a repair, could you kindly post the Bosch part number on the motor? That'd help to see if we can also source a cheaper blower motor replacement for the left.