ToreB

Hi there again Tony.
I see your findings support my theory of the Opamps driving the flap motor directly. I also would think that it is normal that two opamps is connected in a push-pull config to enable the motor to turn either way.
So, you have narrowed the fault into two IC's, that's good!
I'm sure one of them has gone to smithereens, and I would suspect that IC 11 is the one, it is either changed before, or has somewhat different spec and has given up the ghost.
I also suspect there is no fault in your car wiring, remember, this is a common fault in our CCU's.

The pot input on G8 is surely sampled by the microcontroller circuit, therefore you can't find it in the driver circuits. The regulation is surely done in software, and not by a hardware-based closed loop.
You must find a source for the TCA 2465, maybe a fellow Rennlister has a spare or defective unit?
I would try to find two TCA's, and change IC11 first.
Best regards from Norway,
Tore

Tony993

Hi Tore,
I was also thinking of getting a couple of TCA2465 chips so I could replace IC10 and IC11. I think that's a safer approach to avoid having to pull everything apart a second time. I'll plan to do the continuity check on the wiring harness, but I'm expecting this to be OK. I'll check as follows:
G8 -> Servo Pin 3
K4 -> Serov Pin 4
K17 -> Servo Pin 5
If I get a BEEP on all of these I'll place an order for two TCA2465 chips.
Regards
Tony

ToreB

Okay mate.
You could also test the opamp outputs by connecting a voltmeter to K4 and K17 while the CCU is connected in the car.
The voltage should swing from minus to plus 12V (polarity should be reversed) if you turn the temperature **** from min to max and back. This would be the movement required by the flap, opening and stopping the hot air flow.

You could connect the voltmeter between ground and one of the outputs. The voltage should be either +12V or GND. By this you test both output "halves" of both the opamps and maybe determine which opamp that has given up the ghost, possibly both.
The above tests may not be possible to do if the CCU starts some kind of emergency shutdown mode if the response from the servo potentiometer does not follow the commands sent to the motor. You may also have to disconnect one of the leads to the motor to avoid measuring any voltage through the electric windings.

ToreB

Place an order for a TCA2465 where Tony? Have you been able to dig up a source for this?
If so, I'd also be interested.
Tore

Tony993

Hi Tore,
I did the continuity test as planned and got:
BEEP from G8 -> Servo Pin 3
BEEP from K4 -> Serov Pin 4
BEEP from K17 -> Servo Pin 5
So the wiring harness from the G & K connectors seems to be OK.
I saw your suggested message regarding the 'in-car' test which does seem to be a good appraoch. However, since everthing is in pieces on my desk I've decided to replace the two TCA2465 chips (IC10 & IC11). I'll try to find a supplier on-line and I'll let you know who and the cost/availability.
Thanks agian
Tony

ToreB

Good luck Tony, throw in an order for me as well for a handful, and I'll pay you via Paypal or bank transfer.
Maybe you're lucky to get hold of a CCU a s a source for spare parts. I did over here.
Keep us posted for any progress.
Regards from
Tore

Tony993

Hi Tore,
Too late to add a handfull more, I already placed my order. FYI, I couldn't find any retail supplier here in the USA. I ended up using a UK based supplier at www.littlediode.com
My order details were as follows:
SKU Product Item Price Quantity Total
AB439-1 TCA2465 SIP9 $19.40 2 $38.81
My shipping was $13.41 for recorded tracking & 5-10 days delivery!
I expect you could get a better deal on the shipping.
Regards
Tony

Tony993

Hi Tore,
Since I need to wait +10 days for my TCA2465 chips to arrive, I decided to re-assemble the CCU and get it back into the car. So, I ran the checks you suggested with the following results:
K4 (RH mixing flap)
- at start ~86 mV
- turn CCU control to COLD ~ 110 mV (ie little or no change)
- turn CCU control to HOT ~ 110 mV (ie little or no change)
K17 (RH mixing flap)
- at start ~700 mV
- turn CCU control to COLD ~700 mV (ie little or no change from rest)
- turn CCU control to HOT ~11 V (only for about 1 second)
K5 (LH mixing flap)
- at start ~700 mV
- turn CCU control to COLD ~ 11 V (for a second or more)
- turn CCU control to HOT ~ 700 mV (ie little or no change from rest)
K18 (LH mixing flap)
- at start ~700 mV
- turn CCU control to COLD ~700 mV (ie little or no change from rest)
- turn CCU control to HOT ~11 V (only for about 1 second)
The LEFT vent is OK and the CCU seems to be sending a voltage for a HOT setting to open the RIGHT vent.
But, it seems that the voltage is not being sent for the COLD setting to CLOSE the RH vent. K4 appears WRONG!
CONCLUSION: Since K4 BEEPs only with pin 9 of IC10 this seems to point to IC10 as being the bad chip! Does this seem correct?
Cheers
Tony

ToreB

I totally agree with your conclusion Tony. Congratulations, this is great fun!
IC 10 will also almost certainly also be having trouble driving the output to GND, I'll bet both of the output stages in that opamp is gone, therefore no changes in the voltage. When the CCU connect + 12V to one end of the flap motor it will be inert since there is no GND connection in the other end.

I will gather the information you have provided in this thread into a start of a web CCU repair manual.
Best regards from Norway
Tore

Tony993

Thanks for the quick confirmation Tore. I think the CCU Repair Manual is a great idea... perhaps we ought to collaberate and add stuff over time.
Best regards
Tony

Tony993

Hi Tore,
Your soldering tips were very helpful and I was able to remove the old TCA2465 without too much trouble. I needed to use the desoldering braid and a suction bulb to remove the old solder. Then it only needed a little wiggling to get the old chip out. When I soldering the new chip into place I attached a heat sink to it so it didn't over heat.
However, the news is bad!
After replacing IC10, I reconnected the CCU to the car. I then ran the in car tests as I did previously. The readings from K17, K5 and K18 were the same as before... and we think they are ok.
Only K4 changed but it didn't give the expected readings. The results were as follows:
K4 (RH mixing flap)
- at start ~1.7 V
- turn CCU control to COLD ~1.7 V (after an initial change it returns to the same value)
- turn CCU control to HOT ~1.7 V (after an initial change it returns to the same value)
I then pushed the CCU back into the dash of the car and tested the A/C. This confirmed the problem remains ie. only HOT air coming from the RH vent!
I also re-ran the OBD2 diagnostics on the A/C and it continues to show the same fault #32 Right Mixing Flap Motor.
Any thoughts?
Cheers
Tony

Tony993

Hi Tore,
I saw a comment in another Renlist thread about IC11 being common to Left & Right servos. Do you think this could be the culpret even though we thought IC10 was the problem?
Do you think I should also replace IC11?
Regards
Tony