We have a 2000 GMC Safari (130,000 miles) engine is 4.3 liter. The tail lights and rear break lights continually go out. We have replaced the fuses and then it may work for a couple of days but once again goes back out. We have taken it in twice to an electrical car repair shop to the tune of over $300 but they cannot find the problem and just want us to bring it back for longer (and more expensive) visits. We can use the 4 ways. Any ideas?