And this is just my thinking but if you already swapped the relay out with a known good one, I think the diode may be on backwards or in your case not on there at all.
Most diodes I've seen though are on the unit they are trying not to have back feeding thru.
Allen
Here's a novel idea, let's not throw a bunch of parts at the car hoping it will fix the problem and instead spend a little time diagnosing it first.
Life was a little easier when I was just a wrench.
