a993lad

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

osugasman

993/907

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

IXLR8

I'm not saying it isn't the CCU, but at the price of it, I wouldn't jump to conclusions and I'd do some thorough diagnostics first.

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.

77'3.6vram

^Specialized ECU Repair out of FL. They only work on 95' and older ECU's. Gremlins scare me.
WWW.PorscheDME.com-(800)328-1425

ToreB

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

a993lad

Brilliant, thanks Torre B - I was hoping you would respond (was planning to PM you).

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.

ToreB

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

a993lad

Hi ToreB

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

ToreB

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

a993lad

ToreB - Again I must bow to the master - fuse 1 is kaput as you predicted

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

ToreB

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

993/907

Is Fuse 1 the 25 amp fuse?
Mine has done exactly the same thing, but it is the passenger side fan gone kaput.
New one on order, about $500.
Indie says a couple hours labor.

Gordo

911PERVY

Nearer $900, they are £478 in the UK, Porsche only part

f3nr15

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.