vjd3

Can anyone tell me the typical symptoms of a climate control computer failure?

TIA
Vic
95 C4

Buck

Vic, mine went into a failsafe node.

- A/C wouldn't engage compressor.
- Front oil coller blower ran whenever the engine was running.
- Aux blower in the engine compartment continued to run for 20 minutes after every engine start.

I replaced the CCU with a used one and the problems went away. Robin looked at my old one and found a broken trace. He thinks he's fixed it but I haven't had time to test it. If you decide it is your CCU I'll make you a good deal on a refurbished one.

Randall G.

Good morning Vic,

I replaced my CCU because it wouldn't start the oil cooler fan automatically. Every other function worked perfectly.

Buck had an interesting (I mean unfortunate ) case where several components were malfunctioning, and they all shared a common ground connection at the CCU. BTW Buck, I'm happy to hear your problem has stayed fixed!

I've also heard (though not confirmed) that people have had to replace their CCU because it was causing an excessive battery drain.

The following components are controlled by the CCU. If you have a malfunction in any single one, the CCU is a potential suspect. If you have multiple malfunctions (like Buck), the CCU becomes a prime suspect:

-Temperature mixing valve left
-Temperature mixing valve right
-Footwell flap
-Defrost flap
-Fresh air flap
-A/C compressor
-Oil cooler fan
-A/C condenser fan
-Shift valve circulating air flap (mid-year '95 and up)
-Shift flap rear (mid-year '95 and up)
-Rear heater (aux.) blower
-Blower final stage
-Blower motor left
-Blower motor right
-DME coasting shutoff

CCU inputs:

-3-level pressure switch (for A/C)
-Mixing chamber sensor left
-Mixing chamber sensor right
-Evaporator sensor freezing protection
-Rear (aux.) blower temp. sensor
-Oil cooler temp. sensor
-Outside temp. sensor heating
-Back-up signal (mid-95 & later)
-Speedometer

Buck ... it will be interesting to see if Robin fixed your old unit. If he did, maybe he can fix my old CCU?

vjd3

Hmmm ... mine has, for no apparent reason on two occasions, started blowing heat instead of AC, but I can't make the problem recur. I assume there is not a fault code that would be generated if the CCU hiccups?

And today, the AC was not nearly as cold as it has been since I got the car; that could be refrigerant, I suppose, or could be related?

I also note that I have never heard the fan running in the engine compartment after the car is shut down, even on hot days when I was caught in Boston traffic and the oil temp was up on the gauge a bit.

Vic
95 C4

Randall G.

Hi Vic,

It is possible to read out error codes on the CCU, if you have a "Hammer" or equivalent.

As you know, it's going to be difficult to pin-point the problem, if it can't be reproduced. Suppose reading the errors might be helpful ...

Imagine you'll have to monitor your A/C temp. for a few days to see if it's a problem. And, as you've suggested, the cause could be many things other than the CCU (e.g., a burned out condenser fan resistor).

As for the rear blower, your engine has to get really hot for it to run with the ignition off.
The threshold for the blower running is much lower with the ignition on. Next time you feel the engine is very hot: 1) turn off the engine; 2) take the temp. control **** to blue dot; 3) turn the ignition on (engine off), and; 4) listen at the rear blower to see if it's running. It should start in slow-speed when the air at the rear blower is 45C = 113F.

vjd3

Thanks, Randall ... I'll check it out.

Vic
95 C4