Sometimes the fan will not start?

Model number?

Does the fan simply not spin? How do you know it isn't working? Can you see the fan not spinning or is the TV giving you an error message that indicates the fan?

A fan failure can be the fan itself, or another part (usually the part that powers the fan, sometimes a sub board or the fan sometimes connects directly to the power supply).

Without at least a model number, I cannot provide any more help.

The model number of the panasonic TV is PT-52LCX66-K. During start up the power light flashes green the red twice then green again until it becomes solid green and the screen comes on. You can also hear the fan start up during this process. If the fan does not start up the power button eventually flashes orange and the Temp light flashes red, The fan running has been verified visually, by sound and by movement of air at the outlet.
Both intake and outlet vents as well as the fan have been vacummed clean. It is an intermitent problem when the fan starts the TV screen comes on, otherwise it does not come on.

PS: I've opened up the back cover and observed all this and have heard relays clicking on and off.

Well, when the fan is not spinning, you can check to make sure voltage is going to the fan. If not, then you know it's the part supplying the voltage. If voltage is going to the fan, then I would suspect the fan.

As far as parts, I don't have that information in front of me. However, if you call Panasonic, they might provide you the information necessary to find the part. They might even sell and ship the part to you.

At the very least, they should be able to recommend a service technician in your area (I'm biased toward Geek Squad Repair since that's who I work for). I would recommend having a professional service your TV, especially if you are not familiar with electronics repair.