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What model civic is this? ex/lx/si
Just to double check you replaced the power transistor as located in the diagram below.
Sorry, overlooked that.
here is the testing procedure for the system. You either have a bad power transistor - out of the box, bad wire, or the actual heater control panel will need replaced.
You will have to perform the test below with a multimeter. The usual fix for this is the power transistor, but since that didn't work it would leave me to believe you might have a wiring issue as I hardly ever replace the heater control panel. It is possible though.
Hope this helps
The easiest thing to do if you are not able to diagnose with the steps above would be to just go to a junk yard and get a new heater panel assembly for a couple bucks. If it doesn't repair it then you will have to start tracing the wires for a broken wire or burnt wire.
This model civic would depend if the engine says vtec on it or not. vtec would be an EX model, and a DX if it doesn't say vtec. If you don't have power windows or door locks either then it is a LX
Though if you simply have a piece of wire to use as a jumper wire. You can perform some of the tests above pretty easily and could probably narrow it down with that some.