I likewise had a thought to do this, and many thanks for your work to save me time doing it myself.
Got rid of the ground at 87a on both relays and everything works perfectly. I can say the window does go up and down faster but not by much. I'm talking only fractions of a second faster. I am using junk yard parts too so maybe the motor is all worn out. I'll have to see if a newer motor performs the same.
The way I test a motor, is by using a high gauge test harness to jump from the battery straight to the motor. This quickly verifies whether the motor is tired or the wiring needs refreshing. Incidentally, this is how I discovered that the rear window motor was intrinsically grounded. Imagine my surprise when I cabled up the positive (I generally always cable positive first) and the motor immediately started turning! Not only that, but the motor was *strong*, rather than the worn out thing I thought it was. This also incidentally proved the ground was solid, though I'm still inclined to run a ground strap.
I've built a few harnesses for the rear gate glass motors-you HAVE to run big heavy gauge wiring to the back as well as a stout ground to body and motor housing. Mounting the relays in the rear is ideal and recently I've added auto down to my rear gate glass harnesses-no more holding the damn switch lol.
+1 for checking grounds; especially on older rigs where everything grounds out through the body.
+1 for installing the relays in the rear and running a new high gauge positive.
+1 for insuring the new high gauge positive is fused. I'm personally putting a thermal breaker in-line instead -- like the stock, where if you overamp for too long the breaker pops, and then after "a while" will recontact so you don't pop fuses so much.
I'm looking to scavenge a connector set (both ends) from the wrecking yard so minimal modification to the existing harness is needed. Failing that, I'll get two complete sets of "some other" two wire, high gauge, weatherized connectors, and rewire the stock harness and the relays to use that instead.
The existing wiring to the tail gate will carry the switch voltage to the relays. I intend to install the relays in the driver side, rear quarter panel behind the interior panel. The wrecking yard male connector will plug into the female at the tailgate and go to the relay switch control inputs, and the female connector plug into the male connector at the tailgate and go to the relay load outputs (I'll have to double check, but I'm nearly certain that is correct). Obviously the high gauge positive goes to the relay load inputs.
If this new work needs to be bypassed, simply reconnect the original wiring back together at the tailgate (easily accessible, no tools necessary).
I'll post photos of my install when I get it done.
