Horn and reverse lights wont work.

Need to get car inspected but my horn and reverse lights wont work. I have replaced to horn, checked the fuses and it still wont work. On the reverse lights, I have replaced to bulbs twice and checked fuses and still no luck. Crazy thing is, when I put in new bulbs they light up the first time I put it in reverse but nothing after that. There a short or a bad relay anywhere for both problems?
Thanks

Almost sounds like there is too much power going to the bulbs and your blowing em... Checked the lines with a multimeter yet? I would pull out a reverse bulb and a brake bulb and compare the readings of both. I don't know any numbers off the top of my head for the range it should be within, but at least you can get a close comparison of the two since the brake bulbs are fine. Both should be about the same. At least it's a start to diagnosing the problem... Not sure why the horn would go out with this as well... Did you check your grounds to make sure you have a good clean connection there?

I'll check the grounds to make sure. I'll have to find my meter but I will do that also thanks