This VT38A has only been in service a short time. It was installed as a driveway monitor and as such, was activated very frequently.
In opening the unit, I see that the contacts of the relay that supplies 110v ac power to the floodlights are severely burned and the black plastic shield fastened to the side of the contact assembly has experienced an advanced degree of melting. I suppose that the carbon arc that frequently takes place between dirty or burned switch contacts must have created the heat that melted the plastic shield because the melting is immediately adjacent to the relay contacts.
I'll clean and burnish the contacts and test the unit. Even if it works, I would expect the problem to reoccur, probably sooner than before since even after my contact cleaning effort, the contacts will never be as clean as when new.
It's surprising to see this problem in a quite new unit. I have five PR511 motion sensor floodlight units in operation, one of which has been in operation for about five years and is subject to very frequent activation. The other four have only been in operation for about two months, the same period of time that the VT38A was in service. Of these four, three incur only occasional activation while one also experiences frequent activation.
Of the five PR511s, two of them were manufactured at least five years ago, while the other three are of unknown age...just that I only purchased them a couple of months ago.
I replaced the defective VT38A with one of the recently purchased PR511s and we will see if the recently purchased PR511 has the same relay contact problem as the VT38A when used in a frequently activated environment. It could possibly turn out to be yet another 'Made in China' aggravation.