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2002 2500 CTD high beams not working

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  #11  
Old 05-14-2021 | 07:45 PM
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Any input on how to test the MFS to rule it out completely?
 
  #12  
Old 05-14-2021 | 08:29 PM
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Ok, according to theory, (01 service manual...) The Red with Orange trace wires are the ground circuit for the high beams. (cavity C in the headlamp connectors....) With the headlights on, and high beams selected, you should see continuity to ground on that wire. If you don't, check the Black/Orange wire at the beam select switch, see if you have continuity to ground there. (gonna have to pull the column cover for that test.) Also test the light green wire for continuity to ground, also at the beam switch.
 
  #13  
Old 05-14-2021 | 08:30 PM
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See the relevant part of the wiring diagram below. It's important to understand that the lighting works a little different from most other vehicles. Power comes from the PDC directly to the light bulbs. All the wiring shown below the headlamps connects to ground thus completing the circuit. With both light bulbs removed power does not reach that lower part, you can only test the lower part with an ohm meter (resistance to ground) or a test light. With low beams on the violet/white wire at the connector is grounded (already verified working), in the high beam setting the red/orange should connect to ground. If that's not the case follow the red/orange wiring.


 
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Old 05-14-2021 | 08:47 PM
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Originally Posted by HeyYou
Ok, according to theory, (01 service manual...) The Red with Orange trace wires are the ground circuit for the high beams. (cavity C in the headlamp connectors....) With the headlights on, and high beams selected, you should see continuity to ground on that wire. If you don't, check the Black/Orange wire at the beam select switch, see if you have continuity to ground there. (gonna have to pull the column cover for that test.) Also test the light green wire for continuity to ground, also at the beam switch.
are every one of these steps with the lights on and the switch connected?
 
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Old 05-14-2021 | 08:58 PM
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Lights on, but, to test the wires at the MF Switch, just unplug the connector. Makes it easier.
 
  #16  
Old 05-14-2021 | 09:03 PM
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Originally Posted by HeyYou
Ok, according to theory, (01 service manual...) The Red with Orange trace wires are the ground circuit for the high beams. (cavity C in the headlamp connectors....) With the headlights on, and high beams selected, you should see continuity to ground on that wire. If you don't, check the Black/Orange wire at the beam select switch, see if you have continuity to ground there. (gonna have to pull the column cover for that test.) Also test the light green wire for continuity to ground, also at the beam switch.

so I have ZERO continuity with the headlights on or off at the cavity c on the plug, sorry I had to edit this response
 

Last edited by Silverram80; 05-14-2021 at 09:11 PM.
  #17  
Old 05-14-2021 | 09:07 PM
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[QUOTE=Silverram80;3514879]are every one of these steps with the lights on and the switch connected?[/QUOTE

lights on/off I have continuity on the black/orange stripe and also the light green wire.
 
  #18  
Old 05-14-2021 | 09:27 PM
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Bulb plug

Same wire coming into fuse box Red/orange?
 
  #19  
Old 05-15-2021 | 10:54 AM
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Headlights off, neither of those wires should show continuity to ground.... Something is definitely strange there.
 
  #20  
Old 05-15-2021 | 11:52 AM
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Originally Posted by HeyYou
Headlights off, neither of those wires should show continuity to ground.... Something is definitely strange there.

just to be clear :
zero continuity on the bulb plug/ cavity c / red orange wire

i DO have continuity on the light green and orange/ black wires in the column harness.
 



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