Brights flashing with right turn

[J-SQUARED]

Been working on my 85 K1500 front wiring. It was taken apart when I got it so I don't know the previous working condition. I tested all 4 headlights to find all functions work. I did some research and opted for the LMC headlight relay kit to operate my lights. I see there is a strong emphasis on grounds with the headlights so I made sure the grounds were clean and adequate. I have 4 total grounds. 2 on the LMC kit and two in the OEM harness. Since I opted for the LMC kit I went ahead and cut out all of the EOM plugs/wiring and replaced the plug that connects to the LMC kit with a new one. I also opened up all the OEM internal splices in the loom and cut those out and re did them with heat shrink. Some were pretty nasty. I did re-use the OEM wiring to marker/turn and the wiring going to the new plug I put in. Everything looked good and all copper was clean and bright every where I cut into it. I tested everything and it looked good so I re-assembled everything. I went to re-test and found zero functionality on headlights when I turned them on. Park/markers all worked. When I actuated the brights they came on and then when I toggled back the headlights were on. I figured it was a tired MFS and moved on. I then check signals and noticed with low beams everything works as it should. When I turn the high beams on the right turn signal indicator in the cab glows dimly. When I turn the right turn signal on all 4 brights flash on the truck. Although this looks pretty cool, not exactly ideal, lol. I'm about 80% convinced the problem is in the MFS as it is finicky and I can move it around a bit making the headlights turn on and off. My other thought is maybe somehow voltage is back feeding through ground somehow through the turn signal circuit. It was late when I got done last night so I haven't tested anything as I was irritated it gave me fits when I thought I had it whipped...

Is there a simple way to test the MFS?

Oh, rear light harness was pulled out of bed and hanging so I completely cut it out of the equation. I also tested the 4 wires back there and all four function as intended.

What does everyone think?

 

[idrivea2002golf]

I'm assuming you're using incandescent style bulbs for the turn signals. I would start by making sure the bulbs in the 4 corners of the truck are seated correctly and not burned out (parking nor turn). I had an issue, just last weekend, where I upgraded my rears to LEDs and the turn signal turned on the parking lamps for that side. The front bulb was toast and making a connection inside the glass filament. Since relays require about .00001 amp to trigger, it would take almost nothing to send the signal to the LMC harness relay and flash the brights.

 

[Beast496]

Definitely sounds like its in the MFS or in the column interface.

 

[Jgonick]

When I turn the high beams on the right turn signal indicator in the cab glows dimly

My other thought is maybe somehow voltage is back feeding through ground somehow through the turn signal circuit

You are correct-
This usually means voltage is using DK BLU-15 wire as a ground. (Right turn signal)

Check your main ground from your radiator support to the battery.
attachment is a list of main grounds.

Grounds-
Think of a partially clogged drain- a little water everything drains correctly- add too much water and it backs up. If the ground is not sufficient, electricity will try to find another path to ground.(like the turn signal)

 

[J-SQUARED]

I'm assuming you're using incandescent style bulbs for the turn signals. I would start by making sure the bulbs in the 4 corners of the truck are seated correctly and not burned out (parking nor turn). I had an issue, just last weekend, where I upgraded my rears to LEDs and the turn signal turned on the parking lamps for that side. The front bulb was toast and making a connection inside the glass filament. Since relays require about .00001 amp to trigger, it would take almost nothing to send the signal to the LMC harness relay and flash the brights.

i checked a few things when i got home and saw the front marker was just dim... The left turn signal has a new bulb and new base was making poor contact and when i touched it the marker shone brightly again. I had no idea the electrical was so touchy on these trucks!

 

[J-SQUARED]

You are correct-
This usually means voltage is using DK BLU-15 wire as a ground. (Right turn signal)

Check your main ground from your radiator support to the battery.
attachment is a list of main grounds.

Grounds-
Think of a partially clogged drain- a little water everything drains correctly- add too much water and it backs up. If the ground is not sufficient, electricity will try to find another path to ground.(like the turn signal)

Your attachment is helpful. Line 2, 3, and 8 are non existent on my truck. However, when i test ground on the core support studs it seems very strong! I will look into those two and see if that fixes things!

Thanks!

 

[J-SQUARED]

You are correct-
This usually means voltage is using DK BLU-15 wire as a ground. (Right turn signal)

Check your main ground from your radiator support to the battery.
attachment is a list of main grounds.

Grounds-
Think of a partially clogged drain- a little water everything drains correctly- add too much water and it backs up. If the ground is not sufficient, electricity will try to find another path to ground.(like the turn signal)

I should have mentioned for line 2 its exists, just differently. mine is alternator bracket to frame, not battery to frame. I think i can change it pretty easily.

 

[idrivea2002golf]

i checked a few things when i got home and saw the front marker was just dim... The left turn signal has a new bulb and new base was making poor contact and when i touched it the marker shone brightly again. I had no idea the electrical was so touchy on these trucks!

Electrical is a bear and can be stupid touchy. Especially in a 40 year old light socket. There are replacement bulb holders you can crimp on to help. I find using a screw driver to adjust the metal tabs helps too. I'm also a huge proponent of putting a dab of dielectric grease into the socket before the bulb. Doesn't help with contact but it does help with vibration and oxidation resistance.

 

[Ricko1966]

I should have mentioned for line 2 its exists, just differently. mine is alternator bracket to frame, not battery to frame. I think i can change it pretty easily.

As long as the engine has a good ground to the battery,then alternator bracket to frame is fine for chassis ground. But you do need three good grounds 1 to body,1 to engine,1 to frame.