djbooya

I thought my issue was related to the CCU issues posted here in the past. However, I'm not sure if it is the same. With my CCU completely removed and Fuse #1 inserted the inside compartment blower stays running. Is this normal with the CCU removed completely? It does the same thing with the CCU inserted as well. The issue started up about 2 months ago and I've just been dealing without the climate control by keeping fuse #1 out. Obviously, if I leave it in the battery gets drained. I tried removing relays associated to the inside blower with the CCU removed and that didn't seem to help either.

Any other things I should be troubleshooting?

johnbtrask

I had a similar experience. Open up the CCU and clean the connector between the main PCBs and the front panel with electrical contact cleaner (if its disconnected the fan will run all the time) Do the same with the two connectors on the back of the the CCU. Also be sure that all the connectors or properly seated.

djbooya

Tried that didn't seem to work. Is there any self troubleshooting I can do to narrow down if this is indeed the CCU before I send it in to get rebuilt?

mojorizing

Search "blower final stage"

here's a couple

https://rennlist.com/forums/964-foru...-stuck-on.html

https://rennlist.com/forums/964-foru...n-runs-on.html

djbooya

Thanks for the pointers. That final stage blower might just be the issue.

Is that component one that can come up with a diagnostic tool? If yes, is there anyone on the boards near Fremont, CA that has a diagnostic tool that can help me check? I'd prefer to avoid the dealer if possible just to get this diagnosed.

Thanks again!

ToreB

That certainly look like a defective blower final stage. If the output transistors are shorted the blower motor(s) will run continiously. Are both blowers running? The blowers should not run with the CCU out.
There is a feedback line from the final stage to the CCU, and you might have a fault code stored there.
Changing the finals stage is quite an ordeal, see this DIY for details:
http://p-car.com/diy/ac/
Cheers,
Tore

FeralComprehension

This guy can fix your CCU and is sometimes helpful with diagnostics.

He can be irascible.

From his failure modes page (material removed):

"CLIMATE CONTROL TYPICAL FAILURE MODES

PORSCHE

Model 964 - 964 659 04Y XX
very reliable, except for a rare excessive standby current draw,
rear blower fuse (F1 - 30A) blown causing no front blower
except at minimum temperature, limited diagnostics (XX = 00)"

bmohr

I had a blower that stayed on after ignition turn off. Finally did the rear relay jumper mod and it solved the issue. Then my ccu fan would stay on, and I simply disconnected the fan and voila. No more issues. OF course the side effect is the hvac controls take longer to switch i.e if the heat is on and you turn it to cool, it will take a couple minutes to switch over and vice versa.

l.chadburn

I had exactly the same problem in my 1992 C4 Cabriolet.
With the CCU in and the fuse in all blowers were on full even with the ignition off and the key out.
The only way to stop it was to remove the fuse.
I went through to a fellow 964 owner and tried his CCU in my car - worked perfectly.
I then tried my CCU in his car - exactly the same effect.

Solution - I debated whether to pay for a 2nd hand one, however whilst searching the net and talking to other people I came across this website
http://www.autoecu.com
I sent my unit across to the states and it came back with a lifetime warranty.
It is now in my car and works great.
Hope this helps mate

Lee

djbooya

My blowers were running even with the CCU out. I'm hoping it is just the control unit which doesn't look too bad to change according to this page:
https://rennlist.com/forums/964-foru...trol-unit.html

Thanks for the pointers to those CCU shops. I may see if my local parts heaven will let me test a CCU that they have so I can narrow down if it is that vs. the final stage control unit.

djbooya

I didn't get to test a CCU, but was able to test the final stage amplifier unit (96462401002). However, now my fan is not sticking "on". What I am testing now is leaving my car with Fuse 1 in and the final stage amplifier disconnected. I started yesterday with a voltage on my battery of 12.62 and tonight about 30 hours later it is 12.47. Fuse 1 is in and my CCU is disconnected. Is this normal battery drain? If yes, then does this provide any indication that the Final Stage amplifier unit is the issue?

ToreB

It's difficult to answer your question on battery drain based on the voltage of the battery. You have to measure the current draw using an amperemeter to get reliable results. Connect the amperemeter in series with one of the pole connectors on the battery.
Normal current draw in a 964 with ignition off is 50 to 70 mA. (0.05A) An aftermarket alarm can introduce an additional 5 to 50mA.
When measuring, note that open doors will activate the interior lights as well as a relay for enabling the power windows. Also, an open bonnet and/or engine lid will activate the lights there too.
After ignition off the CCU with fan will continue to run for 1 to 10 minutes. (circa 500mA)
An unlocked car will also have the OBD LCD with light turned on in the tachometer.

Therefore, measure the current with all interior/bonnet/engine lights off, lock the doors, and wait for the CCU to turn off. You might consider opening the windows first to avoid having problems getting in due to a problem with immobilizer or similar.

A value of 100-200mA or so can indicate that some of the above mentioned points are active.

If the CCU does not turn off (0.5A) you may have a problem with an internal transistor. It's an easy fix for an electronic wiz.
A car fitted with a 50Ah battery will go flat in about 100 hours with a current draw of 0.5A.
Best regards,
Tore