Ac unit does not goes on at restart

[Frank_j11]

Nope....i mean, if i push auto button, ac switch goes on automatically....but when i turn car off and on, the entire ac unit go off but if i switch auto button again ac button will go on automatically.

[calnorth]

Nope....i mean, if i push auto button, ac switch goes on automatically....but when i turn car off and on, the entire ac unit go off but if i switch auto button again ac button will go on automatically.

It is very difficult to pinpoint this problem. At the moment I think that on press of AUTO the A/C Auto Amp memorises the HAC system state. It probably continues to do that during the use of A/C and heating on a journey. The documents don't say that but if the system was to auto return to the last use state after engine OFF and engine ON (or fault condition) then system state memory would be required.

The A/C Auto Amp is the control of the HAC system. A computational device. Question is:

1. Does it memorise system state
2. If it does not...why not. Is the memory wiped (defaulted) or not active?.

The A/C Auto Amp is a black box which cannot be diagnosed without specific Nissan or other manufacturer test equipment. For this fault I cannot see a specific Nissan test which could mean that a technician would simply change the box..to see what happens? Thats if he followed diagnostics that revealed no other fault.

[Frank_j11]

Hi Calnorth, it you may be interested on that update! I just abbandoned the idea to fix the problem and moved on. Sunday just doing some fix to door panel, i just unplugged after market mirror and windows control unit, doing that 1 of the fuse blow up, i replaced it, put al control unit plugs back and reassembled the door.... Not immediately but after a full day of use, ac unit started working notmally again!!!dont know if related to mirror control unit...but now everything is back to normal

[calnorth]

Interesting @Frank_J11. I've seen a 2003 BMW prevented from starting by a passenger door handle fault. That was a failure of the door handle CAN Bus module to communicate because the door handle had an electrical fault. No handle position signal

The question might be:
Is your Aftermarket equipment failing to communicate correctly with BCM? Its possible Bus Comms from BCM to the A/C AUTO module maybe disrupted? Data corruption in other words. The Bus system is the only common component I can see between A/C AUTO and Mirrors/Windows

The diagnostics documents are not accurate for J11b but I think A/C and Windows and mirrors are on the lesser/slower LIN Bus system because they are not critical. CAN Bus is used for critical systems such as ABS/Brakes etc.

You'll need to keep and eye on the Aftermarket stuff I'd say....