Every morning I start the engine of my car and the air conditioning works properly. But as I drive to my workplace it stops cooling. I've serviced it but have been told that the real cause is that the signal does not reach the valv, which is not an air conditioning issue but an engine failure, which would be a worse and more expensive problem to solve, because catalytic converters, oxygen sensors, spark plugs and coils would need to be replaced. What is your opinion?