Please help me find the way to replace nav system.

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I've read many thread of thread here and I've some problem about to replace Honda accord navigation system from UK accord on my car that I need your suggestion.

My car model is 2004 honda accord without navigation system 3.0 V6 J30A4 engine AT dual climate control from Thailand.

Now i replace 2005 honda accord UK navigation system on my car, everything working fine except head unit won't turn on a/c compressor.

Could you please suggest me about the way to find out this problem?

sorry for my poor English language.
Thank you in advance.