Alright im having several weird electrical issues with my second gen that i believe are due to bad grounding.

When i bought the truck, the situation was as follows: The grounding strap on the left/passenger side of the block attached to the valve cover bolt was disconnected because the valve stud is broken off, The windshield wipers would come on whenever the drivers side* turn signal came on.

i found out about the wipers first and i couldnt find a problem with ground G100 even though thats where people usually fix the wiper short, so i installed a quick and dirty kill switch so that i could turn left And use my washer pump when needed. last night is when i found that ground strap and i attached it to a different stud on the valve cover, the one next closest to the firewall because i managed to get a good ground off of it. Now that ive reattached that ground (which has been after owning and driving the truck for more than a year) the left turn signal indicator in the cab is permanently on, the drivers side parking lamp/turn signal are dimmed down to almost nothing with the lights turned on, and turning on the left signal switch makes the passenger turn signal flash. Hazard light switch makes all four work but the drivers side is still dim.

thats the full list of directly related electrical symptoms but a possibly related one is that the transmission has been having shift problems for about 8 months and i think it may have been related to that grounding strap for the tranny, I dont think fixing the wiring will fix that problem with this unit though because the gears have started going in I assume due to high rpm while getting it to shift. Only adding this piece for potential help with troubleshooting the electrical issues.

 

Think I would have a look at the connectors at the multi-function switch, and maybe even the switch itself.....

 

I went through it once back when I was trying to diagnose a different issue but ill try it again now that i found this new demon, any recommendations on what to check about it, or just which pins are getting voltage, and resistances while its off?

 

If you don't already have the factory service manual, get one from here. Wiring diagrams are in section 8W.

 

Sir, you have just handed me the equivilant of a bible. I have had to hunt through google so many times for each scrap of this info THANKYOU!

 

Following that i went through with my multi today, no issues on the switch unfortunately. Id have loved it to be that quick of a fix, any other ideas where to poke?

 

My rule of thumb is when there's lights on when they shouldn't it's almost always a ground issue, so I think your first guess was pretty good. Try finding the black ground wire at the left turn/marker light and use some wire to connect it straight to the negative battery terminal. See what changes. Another thing you can try is remove the bulb in the left turn/marker light and see if the right turn signal still comes on when it should be the left.

 

Alrighty, sorry for the delay i can only really mess with it on days off so i hope im not breaking some 'thread revival' rule. Pulling the left bulb has seemingly cured a lot of my ailments, as well as in the socket with everything off (no parking lights, turn signals, not even key on) im getting ~.3 (200 scale so, I think that would be 60 ohm?) on one set of prongs, while the ones i believe to be positive are giving me a 13.x, still on 200 scale. I removed the grounding cables behind the headlight and cleaned it all up to bare metal on the stud, its getting a solid ground to battery negative (also around a .3) so im a bit at a loss here. Should i check any passenger side grounds since there are issues on both sides? the service manual is a bit more of a task to navigate than i thought so i apologize for the follow up asks.

I'd also been advised to check the wire looms under the motor to see if anything had melted through within them, gonna tackle that on my next day off aswell.

 

No worries, you're keeping the thread going which is better than some people that post a question never to be heard from again ... Don't get me wrong, it appears electrical stuff is not your strong suit. I can't tell what you're measuring (Volts ? Ohms ? between where ?). On a typical digital multi-meter you select a range, no need to do any math. Setting it to 200 means it will measure up to 200 of whatever you're measuring. Assuming you're looking at resistance 0.3 Ohms from the black wire at the bulb socket to battery negative would be good. If you're measuring from the stud that's not conclusive as you could have "green crusties" in the wire going to it. Also have a good look at the bulb and its socket if there's any corrosion in there.

 

You and DT both have the right idea. I'm guessing you've seen that all the circuits you are talking about, share that common ground, as do I believe, the O/D and ASD, and trailer connector if you have one. They are also spliced into other ground paths as well I believe. Voltage will find it's way home, one way or another. With common grounds, there is more than one way for it to get there. Here's another way to think about it.
Take your VOM, digital is easier to read. Check your battery voltage and remember it. Unhook the positive cable, no power to the truck at all. Hook the negative lead to the positive battery terminal. Now what you are looking for is a drop or difference in voltage along your ground wires. Check bare metal on the body anywhere, you should see battery voltage, that's a good start. The sheet metal looks like one huge wire to the battery. If not, fix the battery ground to the body. Now start checking the affected circuits one at a time. A difference of .1 is not a big deal. A few tenths will dim your lights, much more than that and the voltage will try to back up through another circuit, and pull more amps to get there. Path of least resistance. A large voltage drop, or no voltage at all, fix the bad ground. Also, .1V on a light circuit is no big deal but maybe should be fixed, .2V on a 5V MAP sensor circuit might confuse the PCM. It's relative.
If you need to make a jumper wire to extend your VOM to say the back of the truck, go ahead. Check the voltage again before you set out, you'll see that a decent sized wire 6ft long should change the voltage very little.