Garmin GPS "sees" satellites but can't communicate

I have a Garmin GPS module attached to my Kenwood 3 in 1 dash unit. It has functioned perfectly for several years but, last Sunday, the speed started fluctuating +/- 10kph at a steady 110 and, after I left the car parked for the day, exhibited symptoms where it seeks to be searching for and finding satellites but will not communicate with them. The satellite location screen shows locations but they flash and the signal strength indicators show empty bars but seem to reflect signal strenght. I pulled the module out and checked connections and discovered if I pulled the antenna out, the signal strength for all satellites went to zero. Re insert the antenna and the signal strengths rose again

 

I didn't go digging out the name of the module cos I think this is more a generic fault, probably a chip which needs replacing. It's 11pm here so I'll dig out he Module number tomorrow, if it's critical.
Any ideas froma general point of view ??
John

 

There is a great deal of logic in what you say except for some hiccups since. About a week and a half ago, it came good one afternoon, worked for a couple of hours then failed again. I know when it comes on cos it starts sounding the warning "bell" it gives for School Zone location. It sprung in to life for short periods over a couple of days then, late last week, it came on and hasn't failed since. I did get the impression that it was slow in showing updated location/progress, which it does every second or so but this could simply be an expectation on my part that it was going to fail again. Now it's been working a few days it seems OK, for now. Thanks for yr input