2004 Silverado wacky turn signal

[ledhed75]

I have a 2004 Silverado, 4.3 V6, 2WD, with about 6500 miles on it. Been fairly flawless since I got it in August, except for one weird quirk. When I turn on the left turn signal, and only the left, the hazard lights come on. What's worse is it happens seemingly randomly, and I usually have trouble getting the hazards to go off and the left signal on when making a turn. The right signal and hazards work fine. So far, I've had it back to 2 dealers three times. The first tightened all the grounds, the second replaced the signal control lever, and now the same second dealer can't find anything wrong with it. I'm not imagining the problem; I just can't duplicate it on cue. Can anyone offer me some advice? I suspect the flasher unit under the dash behind the fuse box. However, it's a $40 part, and I hate to be spending my own money on a new truck in warranty. Thanks for your help.