I have been having trouble with the climate control system and was advised to check the auxiliary water pump. Not having time to do so right away, I just disconnected the wire to the pump. Still have problem, but the heat/cooling still worked. I thought that if the pump was disconnected that there would be not much heated water coming into the heater coil, but there seems to be plenty. Is there another one of this little suckers in the system? If not, why bother keeping the pump active, especially when it can damage the CCU?

As for the overall problem, until the car is driven several miles, the outside air exchange keeps cycling off and on. Can hear clicking like a relay going on and off in the dash on the passenger side. Any thoughts on what this is other than replacing the whole climate control unit?

Any thoughts appreciated - RMF

The auxiliary water pump is necessary to keep the water flowing throgh the heater radiator when the engine is at idle.
If you're stucked in traffic (idle) for a certain period of time, the engine water pump does not generate enough circulation to feed the heater radiator. After a while, the coolant cools-off in the heater and you have no more heat.
jack

The auxiliary water pump is there to help in the circulation of the coolant when the engine is at idle. The only thing that can stop hot coolant into the cabin is by using the temperature dial, which controls (I believe) the monovalve. Once the car is running the auxiliary pump is not needed.
What you hear clicking is a malfunction of the CCU circuit board itself.
Here is the remedy:
Take the CCU out, and resolder the contact points (most likely the push buttons).
Look closely for cracks at the solder points (cold solder). Very often with age they come apart, causing the intermittent switching on and off of the fan, and the ac compresor.
I am sure that is your problem. I had the same symptons over a year ago.

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

I see Jackd replied as I was typing.

__________________
1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified

Thank you Pesuazo and Jackd. I'll take a look at the connections.

OK guys - I got the unit out and the bottom removed. All I see is a green circuit board with a bunch of solder joints. None appear to be cracked. Do I remove the board and look further? I have done this in the past and all looked OK. I looked at the actual wire connectors to which the switches attach, but they look in order.

Oh for the days of mechanical controls like the old 75 I have. A lot good all this gadgetry does if it does not work. I do not find it hard to reach over and move a slide lever to adjust the heat or AC.

Has anyone you know of been able to bypass all the electronics and just have basic adjustments?

RMF