STUARTQ

Good question!

I just went to try that and found the battery is in the throws of dying.
I'll get her started tomorrow and report back.

ducnine

Hey STUARTQ, did you ever get this resolved? I have the same situation, nothing turns on anymore.
AC wasn't working for years but fans blew heat and outside air until a few months ago when it seemed to work when fan speed was at highest setting. I did not think anything of it and decide to finally convert from R12 to R134. Took it in and everything was done and mechanic told me as they were testing that it blew a fuse (1), they replaced the fuse and everything was fine for a few days. Now it stopped working altogether. Fuse 1 looks fine so it must be something else. I need to check the other fuses Tore suggests too. So what was your result?

tcsracing1

my CCU is running after shut the car off. it is killing the battery every time. It must be running longer then 20 minutes..

ToreB

Faults in the CCU power switching mechanism is a known problem. If the unit does not shut off as expected an internal transistor needs to be changed. Details here.

Cheers,
Tore

Lorenfb

Not in all cases does this solve the problem.

ToreB

Loren, a good rule of thumb in web forums is to refrain from posting if it does not contribute to the topic.
Even better, write something that helps solving the problem.
T

Lorenfb

Again, replacing the power relay control transistor in either a 964 or a 993 CCU doesn't always correct the problem of the CCU not turning-off
when the ignition switch is cycled to the off position. There are situations where that transistor is OK and the CCU still fails to turn-off when
installed in the vehicle, requiring the CCU to be repaired other than by a simple transistor replacement. This has been the case when repairing
CCUs for 15+ years.

Read here; http://www.systemsc.com/problems.htm , under CCU 964/993

JasonAndreas

Are there any further steps that we can use to troubleshoot this prior to the owner pulling the transistor and testing it themselves or sending the CCU out for component replacement?

ToreB

If the unit does not shut off within 20 minutes, I would start with changing the BC337 CCU power relay transistor.
This is part of my standard refurbish/repair procedure on these units.
Cheers,
Tore

Railmaster.

I vad the CCU fan running and battery drain problem and did the transistor DIY. Priblem solved.

Lorenfb

Check that both G29 (X) & G35 (#15), when measured to G18 (ground), have voltages less than .50 volts with the ignition key removed.
These measurements are taken from the back of the CCU with both CCU connectors plugged in.

Tests with the CCU removed are simple. Check that pins K1 and G18 (grounds) are connected internally. Using a 12V power supply, first connect
G18 to the -12V lead and then connect K2 to the +12V lead. Next momentarily connect +12V to G35 to power the CCU on. Then wait
about 10 seconds and the CCU will turn off. This will verify that the transistor controlling the power relay functions properly. If you need to
actually check the transistor in the CCU, just use the diode function of VOM to measure the two PN junctions (BE/BC) & the CE resistance
of the transistor.

jlucas

I see a couple slightly different appearing pin arrangements for the BC 337, from online pictures its not possible to determine if the pitch of the pins is actually different of it just looks different because of the size of the transistor portion.
Is there a supplier than is know to have a pin arrangement that slides right in?

What is the next item to look at if it's not the BC 337?

Thanks

ToreB

You just bend the pins. Any type will do.
Cheers,
Tore

jlucas

So after the CCU fan being on continuously for a week I went to the garage to get something out of it and now the fan is off. Weird. Does that potentially indicate some other problem?

LM964

964 CCU workings (indiscriminate) are the devil's magic..