4373751 91 dodge d250 headlight switch

[fester_1]

recently i had fixed pcm rebuilt and put in new fuel pump and got truck running again. Well i turned on the headlights and they did not work but the parking lights did. After watching utube video i took 30 minutes to take dash out EASILY not rough. and removed 3 screws to the power mirror adjust to gain access to light switch. Ran ohm test on switch to see how it worked. Here how. Parking lights first since they worked. B2 is hot wire and is red . pull out knob to 1st notch and it energizes R which is yellow black wire. The yellow black wire goes to all 4 corners of truck to light up each lamp, also at this time I becomes energized and the instrument panel lights up which is controlled by the spring coil at front of light switch. I is tan or biege color which run instrument cluster. Also if you look at the LF parking light bulb you will see the yellow black wires for parking lamp and 2 green wires for blinker filament. most likely one for turn signal one for hazard flasher. now the dome light is yellow wire and goes to D. more on that maybe later.
Headlights 12v hot on blue wire which is b3 ,pull knob out 2 notch and b3 energizes U which is blue black wire. Now here is the conundrum , i placed a jumper wire from B3 and U and pull knob to 2nd notch and lights came on. Yeah . NOW THIS CIRCUIT WORKS FINE. Why? If a cuircuit breaker is inside switch why would bypassing this make it work like normal.
Have not worked on high beam yet. But P is always hot and is green black and energizes H which is green. This truck runs lights thru multi function turn signal.
i suspect B1 which is red white energizes D dome but have not tested this yet. I also used hayes 12-31 page at the back of the book.

 

[fester_1]

this light is used in many cars with different color wires for different years . these wire colors only apply to this year of truck

 

[fester_1]

of course didn't get it quite right. One of the blue b3 is jumpered and runs to rear for power via the harness by the steering wheel.The other blue b3 which has the power i couldn't find its origin. One of the U black blue goes to pin 4 of the pcm it would seem i couldn't find where the other U black blue wire goes. 12-7 in hayes book states that low is 18 and 19 and hi beam is 19 and 20 of the multi function switch , But mine is 23 which is green most likely coming from H on switch and then it is transfered to 22 for the high beam which is red orange and runs to lamp. Then 23 again with the multi funcion switch in normal position transfers to 24 the purple white wire and runs to the lamp for low beams , which i have no continuity in this circuit. It is open. I also noticed purple white on pin 6 on pcm. So new multi function switch it is so low beam will work. recap continuity from23 to 22 and not in 23 to 24.
The yellow D is grounded when activated by light switch, which means dome always has power and it is grounded by various switches to activate the dome light.

 

[fester_1]

After looking at pcm diagram , if B3 blue is for license plate light and such and has 12v on it until you pull the light switch knob and then b3 makes contact with U and U goes to pin 4 on pcm ,which is a ground . This makes no sense.