[StephenA]

My ACC reports 1 fault when I run a diagnostic on it. I've replaced the air temp sensor so its not that but what to look at next?

In the morning driving to work I can have the temp set at 68-70 and its fine. Coming home in the dark I need to have it at 80 to make it comfortable so is it the sun sensor thats gone awol?

Steve

 

[adrian]

Does running the diagnostic tell you what faults or just how many?
Would the diagnostic run tell you if the system pressure was low?

 

[Mark B]

I often have to increase the temp slightly when it goes dark, with no faults. I think it's just a feature of the system (or my body!).

I can't remember whether the fault detection is limited to the sensors or whether it includes the actuators as well. It does not include the recirc motor or gas pressure. You can easily check whether the temp and air distribution controls (motors) are working. After that you've got the sun sensor, cabin temp and heater box output temp and anything that I've forgotten. The external temp comes from the outside air temp fed to the dashboard display if my memory is correct.

Unless you can start swapping parts with friend, I'd start looking for a diagnostic computer, assuming they work with the air con.

 

[chris-edinburgh]

at the mo, my acc is doing a strange thing, when its on HI everythings fine, but if i drop the temp down to 27, its like cold, no graduation...
Is everyone elses like that?

 

[Mark B]

Do a self diagnostic check and you'll probably find it reports a fault. Let us know. I'd put money on the cabin temp sensor.

 

[chris-edinburgh]

whats the proceedure for doing a diagnostic as ive never done one before

 

[Mark B]

This page is quite useful reading.

The diagnosis is started by pressing AUTO and <=> together (i.e. top left and bottom right). The temp display then reads zero, and the light on the right hand controls moves from bottom to top. If, before returning to the set temp, the display shows 1, 2 or 3, you have 1, 2 or 3 faults.

 

[StephenA]

and mine shows 1 fault but without a techII or similar I dont know whats causing it.

 

[chris-edinburgh]

well i tried out the diagnostic test at lunch, and there seems to be no fault codes coming up

 

[Mark B]

Then I suggest that your cabin temp sensor might be failing. If I remember correctly, they can go a bit wobbly without failing totally and therefore do not show up a fault. Time to phone a friend to borrow one, or talk nicely to your dealer to ask if you can try one out before commiting the cash. They are about £50 I think.

Alternatively Stephen A might be able to do you a good deal!

 

[StephenA]

I borrowed mine - so that only leaves the other internal sensors as faulty as the external temp one works just fine.

Given the cost of parts I might just stick with having to ramp the temp up after dark.

Steve

 

[sgould]

I find my 9-5 has similar symptoms, possibly overcompensating when the sun goes in.

If the sun sensor is working, is its sensitivity adjustable with Tech2?

This can be done with the 9-5. The software takes a weighted average of the various sensors. Tech2 can change the weighting.

 

[GREY LADY]

Chris-Edinburgh Thanks for the posting,the ACC on my '92 Carly is giving exactly the same symptons.That is full heat on Hi but full cold on any other setting! I've done an ostrich on the fault all through the summer and autumn but now,too late as usual!

 

[ACParrott]

I have a 9000 2.3 turbo, and have been having the same problem, when I tested it first time it came up with no faults, the second time it came up with 1 fault so I tried a third time and again came up with no faults. Recon for the moment I will keep resetting and see what happens.

 

[StephenA]

Mine gets odder. I found on on Friday that if I wait until the car is warmish and then turn off the ACC, leave it for 2 minutes and then turn it back on then it seems to work better in that 70 produces a nice warmth rather than the cold it did before it was cycled...

Steve